We report on the direct observation of spin wave and elastic wave emission from magnetic domain walls in ferromagnetic thin films. Driven by alternating homogeneous magnetic fields the magnetic domain walls act as coherent magnetisation wave sources. Directional and low damped elastic waves below and above the ferromagnetic resonance are excited. The wave vector of the magnetoelastically induced acoustic waves is tuned by varying the excitation frequency. The occurrence of elastic wave emission is proved by a combination of micromagnetic and mechanical finite element simulations. Domain wall emitted magnetostatic surface spin waves occur at higher frequencies, which characteristics are confirmed by micromagnetic simulations. The distinct modes of magnetisation wave excitation from micromagnetic objects are a general physical phenomenon relevant for dynamic magnetisation processes in structured magnetic films. Magnetic domain walls can act as reconfigurable antennas for spin wave and elastic wave generation. The wave orientation can be controlled separately via the domain wall orientation for elastic waves and via magnetization orientation for magnetostatic surface spin waves. Different kinds of applications like spin wave logic devices, signal processors, and devices involving spin wave mediated spin currents are projected. Spin wave excitation in magnetic films is generally based on small lateral antennas for the local excitation of spin waves. One approach towards application oriented spin wave technology focusses on the interaction between spin waves and naturally occurring magnetic microstructures at edges5 and magnetic domain walls6. In that context, symmetric Bloch type domain walls and their spin wave eigenmodes have long been studied7. Theoretical predictions include numeric and analytical models in uniaxial8 and cubic ferromagnetic materials9. Beyond regular Bloch walls, in patterned magnetic thin films different types of magnetic domain walls form. Dynamic spin wave experiments involving magnetic textures range from Néel domain walls for mode localization and guidance of spin wave modes11 to magnetic domain walls as a delimiter for spin waves12 to excited magnetic vortex cores13. Numerical studies suggest the utilisation of domain walls as directional spin wave emitters15. An evidence of such a behaviour was shown only once16. In general, for magnetic thin films dynamic domain wall effects maximize at excitation frequencies around the specific domain wall resonance, which fundamentally is below the ferromagnetic resonance of the magnetic host material19.Relying on local excitation, spin waves offer the possibility to substitute modern day electronics by wave-computing20 by solving the Landau-Lifshitz-Gilbert equation together with the elastodynamic equations using finite element simulations. A piezoelectric element generates local dynamic strain which is transferred to a magnetostrictive material. The simulations predict low loss characteristics for the elastic waves leading to enhanced magnetisation wave propagation lengths as compared to conventional field generated spin waves. The elastic magnetisation wave21 excitation from local piezoelectric antennas due to excitation of alternating strain induced anisotropy in magnetostrictive ferromagnetic layers was shown experimentally22. Alternatively, it was suggested that magnetic domain walls in magnetostrictive materials may also radiate elastic waves from domain walls through magnetoelastic coupling of a moving or vibrating domain wall23. Changes of magnetisation inside the domain wall are directly transferred to local modulation of strain through magnetostriction. Yet, the theoretical study was limited to the MHz-regime. No direct experimental proof for the described modes of wave radiation are reported so far.The possible generation of elastic magnetisation waves from local elastic strains was investigated numerically24. In25 it was shown that elastic waves induce precessional motion of magnetisation in a magnetostrictive thin film deposited on a piezoelectric substrate through strain mediation.The inverse magnetoelastic behaviour, the coupling from elastic waves to magnetisation dynamics has also been investigated. It was shown that elastic waves can interact with magnetic textures, such as magnetic vortices26 by direct time-resolved magneto-optical imaging in conjunction with complementary simulations. We show that domain walls offer an alternative and flexible excitation scheme for elastic magnetisation waves and spin waves.Here, we focus on the excitation of spin waves and elastic magnetisation waves from magnetic domain walls. Domain walls with nanometer core width offer the opportunity for local and reconfigurable spin wave devices, by flexible positioning of the domain walls. We prove the antenna free emission of magnetostatic spin waves and, in particular, elastic magnetisation waves in ferromagnetic films from asymmetric Bloch and Néel type domain walls40Fe40B20 film with a thickness of doFeBC = 120 nm deposited on a transparent glass substrate. To ensure the reproducible generation of domain walls the film is patterned into elongated stripes. Asymmetric 180° Bloch walls form for this ferromagnetic layer thickness26. With the application of a magnetic bias field aligned perpendicular to the domain wall, the domain wall angle is reduced and asymmetric Néel walls form. For the standard experiment . In the centre of the magnetic stripe, a periodic pattern of domains aligned parallel and antiparallel to the x-direction is obtained in the remanent state after applying a magnetic field along x.The investigated model system consists of a magnetostrictive amorphous ferromagnetic Coent Fig. , the axi28 images are displayed in Fig. mx, Δmy, and Δmz are shown for three different times t. The excitation frequency of the sinusoidal varying field Hω,y was set to the domain resonance ωesr/2π = 1.9 GHz. While Δmy and Δmz indicate a strong uniform precession of the domains around the easy axis of magnetisation, Δmx shows only small deviations in time. The main features at the boundary to the closure domains visible in Δmx correspond to the nature of a magnetically charged domain state at the edges. In Δmy and Δmz small periodic features appear inside the excited domains parallel to the domain wall. In the following, we focus on the magnetisation waves emitted by the central domain walls. As we show, these correspond to coherent elastic wave superpositions resulting from wave emission from the dynamically excited domain walls.Dynamic magnetisation component-selective MOKE responseHy = 640 A/m along the y-direction. The magnetisation in the centre domains is tilted by 10° relative to Ku as indicated in Fig. 26, confirmed by MOKE imaging with the sensitivity aligned perpendicular to the domain wall (not shown). The time evolution of the out-of-plane MOKE contrast c⋅Δmz displays wavefronts aligned parallel to the domain wall at the same excitation frequency of ω/2π = 1.9 GHz as used for the experiments shown in Fig. To prove the direct connection of the elastic wave generation to the magnetic domain walls we investigated the dependence of wave excitation on the domain and domain wall configuration. To ensure comparability each domain state was measured at its ferromagnetic resonance. Figure y-direction and reducing the external field Hy to zero. The narrow domain width leads to different effective fields as compared to Fig. 30 of ωesr/2π = 2.5 GHz. From the time evolution of Δmy, it is directly apparent that the periodicity of the elastic waves shifted to smaller wavelengths. The static NDS shows various domain widths, leading to locally varying effective fields. The wavelength of the elastic wave is unaffected by the local effective fields.By changing the domain width and field excitation frequency the elastic waves remain excited. Figure mx component is shown, while the time evolution was recorded with oblique plane of incidence resulting in a superposition of longitudinal and polar magneto-optical contrast (Δmy + c⋅Δmz). Due to the alignment of the anisotropy the domain wall is oriented with an angle of 4.5° to the x-axis. It is directly evident that the wave pattern follows the domain wall orientation and not the orientation of the magnetic track. In order to exclude the possibility of purely microwave field generated waves, an additional control experiment was performed, where the magnetic sample was turned with reference to the excitation source. Figure my component of magnetisation and the time evolution of magnetisation changes shows a superposition of longitudinal and polar contrast (Δmy + c⋅Δmz). The axis of oscillating magnetic field resided along the y-axis, while the long axis of the magnetic stripe was oriented 17° compared to the y-axis.A dependency on geometric factors like stripe orientation is excluded by changing the orientation of the domain walls relative to the excitation field and stripe axis. Figure Hx = 3 kA/m was applied along the x-direction to obtain a nearly saturated domain state. In contrast to the examples before and in the absence of magnetic domain walls no elastic waves are excited. The experiments prove that the wave source is not the microwave field. The elastic wave generation and orientation is directly bound to the existence and orientation of the magnetic domain walls and independent of the alignment of magnetisation.Finally, no magnetization waves form in the absence of magnetic domain walls. An additional configuration without high-angle domain walls is depicted in Fig. ω/2π = 0.7 GHz to ω/2π = 2.5 GHz. Exemplary results extracted from the centre domain at three different excitation frequencies are displayed in Fig. my − < Δmy > x,y is depicted. The change in wavelength of the elastic magnetisation waves, and thus, the dispersion relation of the excited coherent elastic waves are directly imaged. From the images it is evident that the wavelength of the superimposed elastic waves decreases with increasing excitation frequency. We interpret this as neighboring 180°-walls emitting waves with the same wavelength, which create standing wave characteristics inside the domains. For better clarity, reference lines along the wavefronts are drawn in Fig. ω/2π = 0.7 GHz the reference line remains on the node indicating standing wave characteristics. At ω/2π = 1.3 GHz and ω/2π = 1.9 GHz the elastic magnetisation waves exhibit propagating wave characteristics. In the obtained overall set of data, there appears to be no systematic correlation of gradual propagation or standing wave behaviour. Since the same unaltered domain and domain wall structure exhibits, both propagating and standing waves in Fig. The ability to tune the emission of domain wall bound waves is demonstrated by measuring the elastic magnetisation wave characteristics in an identical WDS configuration with the excitation frequency ranging from k and effective field Heff both in-plane and Heff ⊥ k). Two different states of magnetisation are compared in Fig. ω/2π = 9 GHz show the corresponding dynamic response. A line indicates the orientation of the standing spin wave nodes. Figure ω/2π = 9 GHz. It is directly evident that the detected spin waves, and unlike to the elastic waves, now follow the orientation of magnetisation. The magnetostatic spin waves generated at increased frequency are not tied to the domain wall orientation but to the alignment of magnetisation  propagating spin waves. Examples are depicted in Fig. ω/2π = 9 GHz and ω/2π = 10 GHz, respectively. As the wavelengths of these spin waves are below the optical limit of detection, they do not have an experimental counterpart in this work. At frequencies below ω/2π = 5 GHz the low wavelength spin waves are found to be oscillating at higher harmonics of the excitation frequency. At frequencies exceeding ω/2π = 5 GHz this first low wavelength mode is excited directly at the excitation frequency. In addition, a second low wavelength mode is emitted at frequencies equal or higher than ω/2π = 10 GHz, as evident by comparison of Fig. Micromagnetic simulationsω/2π = 9 GHz elastic material from which elastic waves penetrate the material. In the region of the domain wall the magnetisation rotates by π, meaning that there is at least one point in this region where the lateral magnetostriction curve has the highest possible slope. At these points the highest dependence of the dynamic strain on the varying magnetisation is expected. Magnetoelastic coupling leads to a coherent dependence of the elastic response on the dynamic magnetisation response in the domain wall.Figure y-direction. Clear wavefronts can be seen in the magnetic layer. In the substrate the wave amplitude decays rapidly, indicating a surface wave. In contrast, Fig. z-direction. The shown wave pattern is undisturbed in the substrate, but decays in the magnetic layer with positive z-direction. This can be attributed to the free deformation exhibited at the surface of the magnetic film, leading to a reduction in stress along the out-of-plane direction. The excited surface wave profile corresponds to a Rayleigh wave. The resulting stress along y- and z-axis is consistent with the experiment, showing the magnetisation wave response only along these axes. From the stress along the y and z-axis in close circumference to the domain wall  ≈ 5 μm−1. When looking at the simulated integral susceptibility spectrum, no peaks are visible for these modes. No experimental evidence for such spin waves is found as the smaller wavelength spin wave modes are not accessible by MOKE imaging due to the limited spatial resolution of the optical experiment. The regime of elastic (spin) wave generation is not confirmed by the purely micromagnetic modelling.The experimentally found magnetostatic spin wave dispersion is reproduced by the micromagnetic simulations. In addition, a characteristic dispersion of magnetostatic surface spin waves at low wave vector ω/2π = 0.55 GHz up to ω/2π = 2.5 GHz, the upper bound limited by the spatial optical resolution. The extracted ω-k dependence reveals that WDS, NDS, and CDS share a single linear dispersion relation. The dispersion is independent of the state of magnetisation. In an analytical approach, the dispersion relation is compared to the expected linear dependence for an elastic shear wave. For this the velocity of sound c was calculated usingGCoFeB = 70 GPa is the shear modulus of CoFeB33. With the volumetric mass density33ρCoFeB = 7050 kg/m3, a shear wave propagation velocity of c = 3.151 km/s is calculated. The corresponding dispersion relation is added to Fig. c = 3.159 km/s.Experimentally, the elastic magnetisation wave branch is not affected by small changes of the domain configuration. Elastic waves are observed for frequencies ranging from Furthermore, mechanical finite element calculations were conducted for four excitation frequencies from 1 GHz to 2.5 GHz using the micromagnetically obtained magnetisations to calculate the local force densities.Both, the elastic shear wave and the extracted Rayleigh wave, display good agreement with the measured wave dispersion. This confirms the presumed elastic wave mechanism. Moreover, the dispersion relation of the elastic waves provides proof for the domain wall mediated generation of elastic waves.Distinct modes of magnetisation waves are generated from domain wall dynamics. The existence of the waves is confirmed by direct time resolved magneto-optical imaging. Standing magnetostatic surface spin waves in the Damon-Eshbach configuration and elastic magnetisation waves are excited by magnetic domain walls acting as antennas. The experimental investigation shows that the magnetostatic surface spin waves follow the alignment of magnetisation orientation in the domains. In contrast, the elastic waves are independent of the alignment of the excitation field and the state of magnetisation inside the domains. The orientation of the elastic waves is purely bound to the orientation of the domain walls. They are solely and directly connected to the dynamically excited domain walls. The direction of elastic wave propagation can be tuned with the orientation of the domain walls.Together with the experimental evidence, our analysis of the linear dispersion relation clearly shows that the origin of the elastic mode stems from coherent elastic waves generated at the domain walls in the magnetostrictive thin films through magnetoelastic coupling. Origin is a dynamic tensioning inside the excited domain walls of the magnetostrictive material as confirmed by finite element simulations.The discovery of the alternative mode of acoustic wave generation from domain walls could help building broadband and reconfigurable sources of low damped magnetoelastic spin waves for future applications without the need for piezoelectric substrates or elements. The magnetostatic and elastic magnetisation waves emitted by high angle domain walls show that magnetic domain walls can be used as reconfigurable sources for coherent emission of magnetisation waves up to high frequencies into the GHz-regime.a(5 nm)/Co40Fe40B20(120 nm)/Ru(3 nm) layer was prepared by sputter deposition on a glass SiO2 wafer with a thickness t = 800 μm. The Ru covering layer forms a protective layer over the ferromagnetic structures to avoid oxidation and corrosion. Saturation polarisation of the ferromagnetic material is Js = 1.5T. An induced uniaxial magnetic anisotropy of Ku = 1300 J/m3 is introduced by applying a magnetic field of Hepd = 8 kA/m during magnetic layer deposition30. The saturation magnetostriction is λs ≈ 25 × 10−6 34. To ensure the generation of periodic domain walls the film is patterned into elongated stripes with the dimension of 40 μm × 10 mm via standard photolithography and selective ion beam etching. Substrate pieces of 10 mm × 10 mm were cut by wafer sawing from the full wafer.A T35 with an in-plane magnetic field pulse of Hulsep ≈ 3.0 A/m and a rise time of tt,10–90r ≤ 50 ps 27 based on the magneto-optical Kerr effect (MOKE) to a ferromagnetic thin film structure. For all magneto-optical images a specialized magneto-optical wide-field microscope is used that allows not only for static domain imaging, but also for time-resolved observations by using a pulsed Nd:YVO4 laser illumination system with 7 ps pulse width and a repetition rate of 50 MHz for stroboscopic imaging. The laser wavelength is λ = 532 nm and the numerical aperture of the used long-distance objective lens is NA = 0.6. This transfers to a spatial resolution of about 450 nm.To experimentally probe wave emission, we apply time-resolved magneto-optical wide field imagingHω,y. The central wave guide consists of a 160 μm wide and 17.5 μm thick centre conductor. The sample is positioned with the magnetic surface down on top of the waveguide and the sample direction relative to the dynamic magnetic field can be freely adjusted. To influence the domain pattern, and thus the domain wall determined magnetisation dynamics, the magnetic field history is varied in angle and strength.A motorised stage is implemented in the setup allowing for precise and reproducible positioning of a lens, resulting in automatic control of the angle of incidence and magneto-optical sensitivity. A coplanar waveguide is utilised to generate a homogeneous high frequency magnetic field 28. It allows for direct measurement of in-plane and out-of-plane magnetisation components by dynamic MOKE microscopy. In order to measure only dynamic magnetisation contrast each dynamic MOKE image at a phase ϕ is subtracted by an image of phase ϕ − π. The measurement process involves the measurement using two non-zero angles of incidence differing by a sign change and subtraction of those two magneto-optical sensitivities. By following this procedure the polar magneto-optical contrast cancels out, leading to pure magnetic in-plane response. By this also a possible birefringence or photo-elastic effect resulting from the magnetoelastic interaction cancels for the detection of the pure in-plane magnetisation components, as the reflection coefficients are symmetric for two opposing angles of incidence36. Only magnetic contrast changes are visible in the quantitative dynamic in-plane images .The dynamic change of individual magnetisation components is probed by a component selective imaging process3 31 were used to explain the experimental results. In accordance with the experiments, in the numerical simulations a two-dimensional two domain state of domain width w = 25 μm was simulated in the y,z cross-section plane. Periodic boundary conditions along x- and y-directions were applied. A grid size of 1 × 12500 × 30 with a cell size of 4 × 4 × 4 nm3 was used. Calculations were performed with an exchange constant A = 15 pJ/m37, a damping constant α = 0.008, an uniaxial anisotropy Ku = 1300 J/m3, a saturation magnetisation of Ms = 1200 kA/m and at a temperature of T = 0 K. The domain wall was excited with a magnetic field amplitude of Hω,y = 145 A/m. The homogeneous high frequency field was applied at frequencies ranging from ω/2π = 0.5 GHz to ω/2π = 12 GHz. In order to gain comparable results and gain purely dynamic magnetisation response Δmy each simulated time frame at excitation phase ϕ is subtracted by the corresponding time frame at excitation phase ϕ − π.Two-dimensional micromagnetic simulations using mumax26λs = 25 ⋅ 10−6 is the saturation magnetostriction, mi,k are the components of the magnetisation vector and δik is the Kronecker delta. In order to calculate the elastic response of the material on the domain wall excitation, we calculated the force density f caused by magnetostriction38:39 calculation.The components of the magnetostrictive strain tensor 40Fe40B20 with a length of 50 μm. To reduce the computation time, the substrate was assumed to be infinitely thick, hence after 10 μm of the substrate low reflecting boundary conditions are applied. These conditions are as well applied for the left and right boundary of the simulation area to avoid standing waves due to reflection. The excitation area around the domain wall is placed in the middle of the magnetostrictive layer with a size of 808 × 116 nm2 with a cell size of 4 × 4 nm2, where the calculated forces are applied as a boundary load. Due to the numerical gradient evaluation, the force input was reduced by one cell along the z-direction compared to the micromagnetically simulated magnetisation distribution. For the calculation the following isotropic material parameters were used a Young’s modulus of ECoFeB = 182 GPa, a Poisson’s ratio of νCoFeB = 0.3, and a density of ρCoFeB = 7050 kg/m3 33, and respectively Eglass = 82 GPa, νglass = 0.206, and ρglass = 2510 kg/m3 40.The COMSOL Multiphysics® model consists of a 116 nm thick layer of a magnetostrictive amorphous ferromagnetic CoThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.Supplementary informationSupplementary video 1Supplementary video 2Supplementary video 3


In silico approaches have become indispensable for drug discovery as well as drug repositioning and adverse effect prediction. We have developed the eF-seek program to predict protein–ligand interactions based on the surface structure of proteins using a clique search algorithm. We have also developed a special protein structure prediction pipeline and accumulated predicted 3D models in the Structural Atlas of the Human Genome (SAHG) database. Using this database, genome-wide prediction of non-peptide ligands for proteins in the human genome was performed, and a subset of predicted interactions including 14 PDZ domains was then confirmed by NMR titration. Surprisingly, diclofenac, a non-steroidal anti-inflammatory drug, was found to be a non-peptide PDZ domain ligand, which bound to 5 of 15 tested PDZ domains. The critical residues for the PDZ–diclofenac interaction were also determined. Pharmacological implications of the accidental PDZ–diclofenac interaction are further discussed.  Many protein–ligand docking programs have been developed and are widely used -NH4Cl as the sole nitrogen source. The harvested cells were resuspended in lysis buffer  and disrupted by sonication. The supernatant was applied to a DEAE–Sepharose  column and then affinity purified by Glutathione Sepharose 4 Fast Flow  chromatography. The GST tag was removed by PreScission protease on beads. The purified proteins were concentrated to ~0.2 mM and dialyzed with 5 mM MES (pH 6.5).The expression vectors for the recombinant GST-tagged form of PDZ domains listed in 1H–15N SOFAST-HMQC spectra with and without ligands were measured. In each titration experiment, a final concentration of the compound at 0.5 mM (cocktail or single compound) was added to the proteins. The signal assignment of mZO1-PDZ1 (the first domain of mouse ZO1) has already been published [1H–15N SOFAST-HMQC spectra were calculated according to the formula {Δδ(1H)2 + [Δδ(15N)/7]2}1/2. The chemical shift changes were then mapped onto the structure of mZO1-PDZ1 (PDB:2RRM) using OtMG/CCP4mg graphic software [NMR experiments were performed on a Bruker Avance III (600 MHz) NMR spectrometer  equipped with a cryogenic triple-resonance probe. For the titration study, 25 μM PDZ domain sample was dissolved in 300 μL of 5 mM sodium–MES buffer (pH 6.5), and the ublished . All NMRublished  and analublished . All chesoftware .in silico screening, although eF-seek failed to predict some of the newly found PDZ–ligand interactions. Since eF-seek is an evidence-based binding site predictor for only ligands which appear at least once in PDB, eF-seek is not ideal for virtual screening in drug discovery. In contrast, eF-seek is sensitive to shapes and charge distributions of the protein surface, thereby making it useful for comparing proteins in terms of protein–ligand interaction. Finally, with these features, eF-seek is efficient for drug repositioning and/or adverse effect prediction.Three non-peptide PDZ domain ligands, diclofenac, flufenamic acid, and fusidic acid, were found to bind to more than 4 PDZ domains at their canonical peptide binding sites. We examined 10 commercially available compounds, which were selected by genome-wide eF-seek prediction against all PDZ domains in the human genome. This ratio is higher than that of the usual NMR-assisted


Covalent organic frameworks (COFs) are an emerging class of functional nanostructures with intriguing properties, due to their unprecedented combination of high crystallinity, tunable pore size, large surface area, and unique molecular architecture. The range of properties characterized in COFs has rapidly expanded to include those of interest for numerous applications ranging from energy to environment. Here, a background overview is provided, consisting of a brief introduction of porous materials and the design feature of COFs. Then, recent advancements of COFs as a designer platform for a plethora of applications are emphasized together with discussions about the strategies and principles involved. Finally, challenges remaining for this type material for real applications are outlined. They are fundamental in a diverse range of applications, from structural materials to energy technologies.1.22O is available for bond self‐correction. A boronate ester‐linked network designated COF‐5, obtained from the condensation of 1,4‐benzenediboronic acid (BDBA) and 2,3,6,7,10,11‐hexahydroxytriphenylene (HHTP), which represents a prototypical 2D COF structure. The COF‐5 network adopts a hexagonal unit cell with the porous sheets stacked in a nearly eclipsed fashion with a 0.34 nm interlayer spacing. This structure, as well as all subsequent 2D COFs, was assigned by comparing its refined powder X‐ray diffraction (PXRD) pattern with simulated patterns of eclipsed and staggered stacking arrangements; no single‐crystal X‐ray structure of a 2D COF has been reported so far. COF‐5 exhibits permanent porosity with a Brunauer–Emmett–Teller (BET) surface area of 1590 m2 g−1, a narrow pore‐size distribution centered at 2.7 nm, and excellent thermal stability (to temperatures up to 500 to 600 °C). The other 2D COF, COF‐1, derived from the self‐condensation of BDBA was reported simultaneously with COF‐5, and remains the single example of staggered interlayer stacking. These successes have led to the expansion of COF materials to include organic units linked by strong covalent bonds such as B—O, C—N, and C—C.] Due to the diversity of organic synthesis, the enormous possible design space available within COFs provides virtually unlimited room for imagination, allowing designed incorporation of different functionalities for numerous potential applications. In contrast to other porous materials, the control of geometry, size, and functionality of the building blocks can be used to design not only the atomic layer structure, but also the framework structure. In this context, the properties of COFs can be designed using specific structures of knots and linkers in the topology diagrams. Thus, COFs offer a combination of properties not found in other materials.COF synthesis was inspired by prior advances in other classes of framework materials and designed noncovalent assemblies, in particular from the concepts used for MOF synthesis. One of the challenges of extending MOF design concepts to covalently linked polymers is that many organic functional groups, characteristically possessing high bond strengths, do not undergo dynamic exchange processes as readily as coordination complexes. As a result, linking organic molecules by covalent bonds into extended solids typically generates amorphous, disordered materials.[[qv: 5a]] The attainment of crystals was accomplished by several techniques in which a balance is struck between the kinetics and the thermodynamic reversibility of the linking reactions. This breakthrough was made by Yaghi and co‐workers when they reported the very first two COF members.1.2.1−3, lower than any other crystalline solid.COFs are constructed solely from light elements that are expected to offer high gravimetric performance for guest molecule and energy storage. The density for COF‐108 is only 0.17 g cm1.2.2COFs are connected by robust covalent bonds and thereby show enhanced stability compared to most MOFs. Recent advances in reinforcing the COF structures include providing hydrogen bonding interactions, weakening the polarity of the amine bond, introducing enol‐keto tautomerizations, or utilizing a Michael addition–elimination/benzoxazole pathway.1.2.3COFs are crystalline, offering a strategy to position functional groups in a highly controlled and predictable manner. This establishes the structure–property relationship and enables characterization using diffraction techniques. This structural uniformity is also potentially attractive for optoelectronic devices and catalysis.1.2.42 g−1 have been reported for 2D and 3D COFs, respectively.COFs have periodic and uniform porosity allowing for better performance in gas separation or catalysis where usually full access to the pores is required. Surface areas exceeding 3000 and 5000 m1.2.5COFs' versatile properties can be adjusted from a thoughtful selection of building units prior to synthesis. Therefore, scientists can manage the composition and the structural architecture in a crystalline and porous material with precise control over chemical functionality, density, and spatial arrangement of the active sites. Recent developed strategies, such as incorporating monomers with reduced symmetry, multiple components with differing lengths, more than one bond forming process, or using metal coordination approaches, enable the COF structures to be more sophisticatedly controlled. Depending on the desired properties and functions, COFs can be designed at three different structural levels: pore design, skeleton design, and the complementary design of pores and skeletons.In this review, we will highlight representative examples that leverage the above features to construct COFs with promising properties. We aim to give a concise overview about the multitude of properties of COFs and applications that have been realized so far, providing inspiration for further development and utilization of these intriguing structures. A main focus will be on insights regarding the task‐led design. Beyond assembling diverse molecular linkers in coupling reactions to generate the frameworks, additional functionality can be incorporated into COFs through postsynthetic modification as well as integration with other functional materials and these will be introduced along with their specific application. Challenges remain for this type of material pertaining to their practical applications, such as convenient methods to process COFs into useful forms and scalable synthesis, which will be introduced in the last section.22.12 storage capacity can be achieved in COF‐105 at 80 bar.[[qv: 13a]] This value obviously outperforms representative MOFs whose H2 uptake values were 7.0 and 7.1 wt% for MOF‐177[[qv: 14a]] and MOF‐5,[[qv: 14b]] respectively. With respect to volumetric capacity, COF‐102 boasts the maximum excess H2 uptake of 40.4 g L−1 at 100 bar, close to the target of 45 g L−1 identified by the Department of Energy, ranking it among the highest performing materials in terms of gas storage capacities.[[qv: 14c]] Stimulated by these theoretical results, Furukawa and Yaghi demonstrated the first adsorption studies of H2, CH4, and CO2 relevant to clean energy applications in COFs.−1, respectively, at 77 K and 85 bar, rivaling some of the best MOFs and other porous materials in their uptake capacities. These results suggest that COFs give great potential in the quest for practical gas storage materials.Inspired by an escalating interest in MOFs and other porous materials for storing, separating, or sequestering technologically relevant gases,3 are of interest for industrial ammonia transportation, separation of NH3 from N2 and H2, personal protective equipment, as well as air remediation. Considering the high density of Lewis acidic boron atoms, present in boroxine (B3O3) or boronate ester (C2O2B) rings in some COFs, these sites provide a unique adsorbent surface ready for trapping Lewis basic gases, such as ammonia, reminiscent of the classical ammonia–borane coordinative bond , significantly outperforming the state‐of‐the‐art materials Zeolite 13× (9 mol kg−1) and Amberlyst 15 (11 mol kg−1). A noteworthy feature of COF‐10 is that the adsorbed NH3 can be completely removed by heating to 200 °C under a pressure of 0.1 torr and repeated adsorption/desorption cycling did not result in any significant loss of NH3 uptake capacity for at least three cycles. However, broadening and a decrease in intensity of the PXRD patterns of COF‐10 subsequent to each cycle indicated that the ammonia adsorption resulted in turbostratic structural disorder and increasing disorder in packing between layers during cycling. This was further evidenced by the decreasing mesoporous character as reflected by its gradually lowering N2 uptake capacity. To eliminate the issue of irreversibly disordering lattice packing during cycling, using Lewis acidic 3D COFs might improve the long‐term performance, given that their entire frameworks are connected by covalent bonds.In addition to gas storage, COFs are also useful for the capture and storage of harmful gases. Due to its irreplaceable role in global agriculture and industry, ammonia is one of the largest volume chemicals on the planet, yet it is a highly toxic and corrosive gas even in small concentrations.nd Figure1a. Giv3 uptake capacity of 6.85 mmol g−1 at 1 bar, 298 K, which increases nearly 50% to 9.34 mmol g−1 for the material with 17% acid functionalization. Furthermore, the authors incorporated Ca, Sr, and Mn divalent cations to the pore surface by treatment of the best performing 17% acid‐functionalized COF with corresponding metal solutions. The ammonia uptake capacity was significantly enhanced in all three cases, particularly for the strontium incorporated material, with an equilibrium ammonia capacity of 14.30 mmol g−1 under identical conditions. These results provided a way to increase the interaction strength between the COF materials and the target molecules and thus improve the uptake capacity and selectivity.Recent studies have illuminated the impact of open metal sites on the ammonia capacity of MOFs, but a vast majority of MOFs cannot survive under ammonia exposure. To address this issue, the advantages of both MOFs and COFs can be combined, as the covalent bond constructed backbone provides stability, while the introduction of metal ions with accessible coordination sites confers a high affinity for ammonia. In this context, Yang et al. reported functionalization of an imine‐linked 2D COF with carboxylic acid groups decorating the pore walls with a controlled amount by using a multicomponent condensation strategy.Figure2 g−1, the highest value reported to date for a COF. Metalation was readily achieved by treatment of the COF with Ni(COD)2 toluene solution, yielding Ni‐DBA‐3D‐COF with a retained surface area , McGrier and co‐workers demonstrated the synthesis and metalation of a mesoporous 3D COF containing DBA.2 and mitigate this environmental dilemma is an urgent task. Since the first report on CO2 adsorption of COFs in 2009, great efforts have been made to improve the CO2 capture performance of these materials.[[qv: 6k]] Despite great progress achieved, there is still room to be improved. The performance of COFs as CO2 sorbents in terms of both uptake capacity and selectivity are not comparable with their analogues, MOFs, which is primarily due to their binding site deficiency and less suitable pore sizes. The following are some representative works to address these challenges.The development of effective technologies or strategies that can efficiently capture CO2 g−1), large pore volume, and relatively small pore size (0.94 nm) as well as abundant nitrogen sites on the pore wall, ACOF‐1 exhibited a high CO2 uptake capacity of 177 mg g−1, superior to many representative COFs, even those with higher surface area.With the consideration that azine‐linked COFs not only possess exceptional stability, but also can be easily predetermined to make smaller pore sizes due to the short structural length of the azine unit, Liu and co‐workers synthesized an azine‐linked COF, ACOF‐1, by Schiff base reactions between hydrazine and 1,3,5‐triformylbenzene.3‐BDBA and 1,4‐benzenediboronic acid at various rations, yielding a series of isostructures of COF‐5 with controllable azide densities (X%N3‐COF‐5).Figure2 over N2 for the surface‐engineered COF‐5 was compared with that for the pristine COF‐5. It was shown that both the type and the content of functionalities have a great effect on their adsorption. For example, a fivefold increased selectivity in comparison with COF‐5 was found in 25%PyTrz‐COF‐5 and 100%AcTrz‐COF‐5 showed a 16‐fold increase in selectivity relative to that of COF‐5. Given the great improvement, this strategy opened a new avenue to improve the gas adsorption/separation performance of COFs. Later, they extended the pore surface engineering strategy to imine‐linked porphyrin COFs to enhance their affinity toward CO2.2 adsorbents. Twenty COF materials with different types or density of functionalities were synthesized by Cu catalyzed click reactions between the ethynyl groups in the COFs and various azide compounds. Due to the strong interactions between the amino groups and CO2 by the formation of acid–base pairs, a significant enhancement in CO2 adsorption was observed for the amine functionalized COFs, even tripling that of the pristine COF.Given the importance of pore surface properties on the sorption behavior toward specific gas and thereby the capacity and selectivity, tailor‐made interface of COFs would offer numerous possibilities for gas storage and separation.2.2In view of the continuous environmental and economic challenges in the world, there is a pressing need to develop a more sustainable chemical industry by implementing efficient chemical transformations. This can be done by developing new catalytic materials to improve the outputs and thereby lower the overall process costs. The use of porous materials as heterogeneous catalysts is of great interest because they offer the advantages of conventional heterogeneous catalysis combined with greater accessibility of active sites.2 solution resulting in only minor changes to its PXRD pattern  and 1,4‐diaminobenzene, was newly designed to meet the prerequisite as a catalyst, that is, stability and the ability to incorporate catalytic active sites.rn Figure4. The 2, with different size can be selectively coordinated with the two nitrogen ligands in the COFs. The large and rigid Rh(COD)Cl molecules which do not fit into the space between adjacent COF sheets were first introduced into the COFs to coordinate with bipyridine moieties and then the smaller and more flexible Pd(OAc)2 molecules were incorporated to coordinate with the residual bipyridine moieties, if have, or amine moieties. The bimetallically docked COFs showed excellent activity in a one‐pot addition–oxidation cascade reaction.Gaining enlightenment from this work, Gao and co‐workers nicely demonstrated that COFs provide an intriguing platform for precise control of the number and position of the catalytic metal ions. To show this, a series of 2D COFs containing two different types of nitrogen ligands, namely imine and bipyridine, with controllable content were synthesized by a three‐component condensation system.FigureWith the knowledge of the basicity of an amine bond formed by the alkyl amine and aldehyde species as well as the microporosity of 3D COFs, Yan and co‐workers designed and synthesized two new 3D COFs by condensing a tetrahedral alkyl amine, 1,3,5,7‐tetraaminoadamantane (TAA) with triangular building units TFB or triformylphloroglucinol (TFP) for their use as base catalysts Figure5.28 ThGiven the important role of acid catalysis in industry, the development of efficient solid acid materials is highly desired. Zhao and co‐workers reported the de novo synthesis of a sulfonated COF (TFP‐DABA) by condensation between 1,3,5‐ TFP and 2,5‐diaminobenzenesulfonic acid (DABA).2 as an abundant, inexpensive, and nontoxic C1 source could contribute to the sustainable use of natural resources.2 and epoxides, a COF material  containing catechol as the hydrogen bond donor was constructed by Schiff base reactions of 5,10,15,20‐tetrakis(4‐aminophenyl)‐21H,23H‐porphine (Tph) and 2,3‐dihydroxyterephthalaldehyde (Dha). The resultant COF showed excellent activity toward cyclic carbonates and oxazolidinones with the assistance of tetrabutylammonium iodide in metal free conditions.Employing CO2 transformations, to install ionic moieties, the COFs with different phenol content on their channel walls were synthesized as intermediates by three‐component condensation of 4,4′,4″,4′″‐ tetraaniline (PyTTA) with 2,5‐dihydroxyterephthalaldehyde (DHPA) and 1,4‐phthalaldehyde.X%‐Py‐COFs , where X% represents the molar percentage of DHPA used in the dialdehyde blend. Through the Williamson ether reaction between (2‐bromoethyl)triethylammonium bromide and phenol group in [HO]X%‐Py‐COFs, ionic moieties were then immobilized onto the COFs named as [Et4NBr]X%‐Py‐COF. Considering the trade‐off of density of ionic moieties, as well as the crystallinity and surface of the functionalized COFs, [Et4NBr]50%‐Py‐COF was chosen as a representative sample for detailed catalytic evaluation. Under very mild conditions, at 30 °C and 1 bar CO2, it can efficiently catalyze the formylation of various amines with CO2 in the presence of phenylsilane (PhSiH3) with good recyclability.Considering that quaternary ammonium salts have been proven to be efficient catalysts for CO2 to CO. Initially, a model COF material (COF‐366‐Co) by the imine condensation of 5,10,15,20‐tetrakis(4‐aminophenyl)porphinato]cobalt [Co(TAP)] with 1,4‐benzenedicarboxaldehyde (BDA) was synthesized for electrocatalysis studies . Considering that a larger pore size would allow for higher capacity of carbon dioxide adsorption inside the framework as well as more efficient exposure of the electroactive sites to the reactants, a modular reticular approach was used to further improve the performance of COF‐366‐Co. To expand the pore size, biphenyl‐4,4′‐dicarboxaldehyde was used as the strut instead of BDA to condense with Co(TAP) for synthesizing the COF. As expected, this expanded COF exhibited improved catalytic efficiency over COF‐366‐Co, giving a TON value of 48 000 after 24 h. Taking advantage of the tunable synthesis, to further optimize the performance, the authors introduced building‐block heterogeneity through a multivariate strategy to maximum the utilization efficiency of active sites. To achieve this, catalytically inactive isostructural copper porphyrin units were partly replaced by Co(TAP) to dilute its concentration with the purpose of increasing the proportion of the active sites exposed to the reactant and thereby improve the turnover frequency on a per‐cobalt basis. Accordingly, two bimetallic COF‐367 derivatives with the Co proportion of 10% and 1% in all metal sites were synthesized named as COF‐367‐Co(10%) and COF‐367‐Co(1%), respectively. A substantial improvement with each tenfold dilution of cobalt loading was observed. Specifically, at the beginning 4 h, COF‐367‐Co, COF‐367‐Co(10%), and COF‐367‐Co(1%) afforded the turnover frequency (TOF) values of 1900, 4400, and 9400, respectively. To further enhance the active sites accessibility, COF‐366‐Co thin films were in situ grown on glassy carbon to improve electrochemical contact and thereby the catalytic efficiency. Under the same electrolysis conditions, a seven times increase in terms of TOF was afforded compared with the corresponding powder sample. Subsequently, the performance of the catalysts was further systematically tuned by modification of the reticular structure and the current density for CO formation increases from 45 mA mg−1 for COF‐366‐Co, to 46 mA mg−1 for COF‐366‐(OMe)2‐Co, and up to 65 mA mg−1 for COF‐366‐F‐Co.Yaghi and co‐workers demonstrated an elegant example of modular optimization of COFs to prepare a high performance catalytic material as demonstrated by aqueous electrochemical reduction of COes Figure6. It wFigurem HCl), and strong bases (14 m NaOH), was synthesized by condensation of dimethoxyterephthaldehyde (DMTA) and 1,3,5‐tri‐(4‐aminophenyl)benzene (DMTP) under solvothermal conditions. In addition to the exceptional stability, this material also possesses high crystallinity, giving a BET surface area of 2105 m2 g−1, which is among the highest for 2D COFs, combined with a very narrow pore size distribution centered at 3.3 nm. All of these properties exceed the state‐of‐the‐art approaches to stabilize COFs including the introduction of enol‐keto tautomerizations or hydrogen bonding interactions to the COF skeletons. Encouraged by these intriguing properties, the authors further explored its application in chiral catalysis. To introduce chiral centers and to adjust the density of active sites, a three‐component condensation system with 2,5‐bis(2‐propynyloxy)terephthalaldehyde (BPTA) and DMTA as edge units was employed to prepare the intermediate [HC≡C]x‐TPB‐DMTP‐COFs  and NaOH (14 m) solutions. Catalytic evolution results revealed that the resultant catalysts exhibited excellent activities and enantioselective selectivities as well as broad substrate tolerance. Due to its large pore size, it permits the face‐on attack by nitrostyrenes to the catalytic sites and thereby the high activity, placing them among the most efficient Michael reactions catalysts reported thus far.The development of robust heterogeneous chiral catalysts that can perform asymmetric reactions with high efficiency and superb enantiomeric selectivity is of great importance.s Figure c. FollowS)‐4,4′‐(2‐(pyrrolidin‐2‐yl)‐1H‐benzo[d]imidazole‐4,7‐diyl)dianiline with TFB or TFP yielded two chiral COFs named as LZU‐72 and LZU‐76, respectively. Both of them showed high crystallinity and relatively high surface areas of 1114 and 748 m2 g−1, respectively. Due to the robustness of β‐ketoenamine linkages in LZU‐76 against acidic conditions, it was then chosen for catalytic tests. In the asymmetric aldol reaction, LZU‐76 can efficiently catalyze the reactions between a variety of aromatic aldehydes and acetone in the presence of trifluoroacetic acid with competitive enantioselectivity in relation to its homogeneous counterpart.Compared with postsynthetic modification, the utilization of de novo approach is expected to offer better control with respect to the grafting degree and homogeneity of functionalities. Wang and co‐workers reported the first example of the direct construction of chiral COFs from chiral building blocks.Cui and co‐workers also described the preparation and catalytic behavior of a series of 2D COFs bearing chiral organocatalysts such as L‐proline and L‐imidazolidine.FigureiPr)4, this chiral COF showed superb performance in the asymmetric addition of diethylzinc to aldehydes, outperforming the corresponding homogeneous analogue (TADDOL/Ti) in terms of both activity and enantioselectivity. Moreover, due to their ordered microporous structures, obvious size selectivity toward reagents was observed in the COF‐based catalyst, given the fact that less than 5% conversions were detected with the CCOF/Ti catalyst in coronenyl transformation which was much lower than the 64% conversion obtained with homogeneous TADDOL/Ti. Later on, a 3D chiral COF based on TADDOL was reported by the same group through the condensation of tetra(4‐anilyl)methane with tetraaldehydefunctionalized TADDOL.In comparison with the chiral functionalities dangled on the framework, it is envisioned that those incorporated in the frameworks are expected to have a high level of synergism with the networks and thereby lead to superior performance. Cui and co‐workers demonstrated the construction of 2D COFs with chiral functionalities embedded into the framework by Schiff base condensation reactions of enantiopure tetraaldehydefunctionalized TADDOL  and 4,4′‐diaminodiphenylmethane Figure8.39 AfFigure3‐symmetric trisalicylaldehydes with or without the tert‐butyl group.2·2H2O was in situ introduced as a template during the COF synthesis. Given the relative liability of Zn—O/N bonds and the accessible channels as well as the robustness of the COF structure, a variety of metal species can be incorporated by postsynthetic metal exchange with negligible change in structure integrity. As a result, numerous efficient Salen‐based chiral catalysts can be designed on demand. Specifically, to catalyze the cyanation of aldehydes, V species were installed; to realize the asymmetric Diels–Alder reaction, Co species were immobilized; to fulfill a one‐step cascade reaction, in which epoxidation of the alkene was followed by ring opening of the epoxide to afford the amino alcohol, Cr and Mn species were simultaneously introduced. Moreover, the resultant catalysts can be readily recycled with retained catalytic performance in terms of both activity and selectivity for at least 5 times.The Salen unit represents one of the most important ligands in coordination chemistry. Wang and co‐workers demonstrated the first example of a Salen‐based COF material.x‐COF, where x stands for the number of N in the central aryl ring of the precursor aldehydes. Progressively enhanced hydrogen evolution was observed with increasing nitrogen content in the frameworks, giving 23, 90, 438, and 1703 µmol h−1 after 8 h for N0‐COF, N1‐COF, N2‐COF, and N3‐COF, respectively. These results indicated about fourfold increase in hydrogen evolution with each substitution of C—H by N in the central aryl ring of the COF platform and N3‐COF rivaled the state‐of‐the‐art carbon nitride photocatalysts. To rationalize the observed trend and to provide insights into the mechanism underlined, using a combination of spectroscopic and theory calculation studies, it was revealed that the substitution of the C—H moiety with nitrogen atoms leads to a change in the dihedral angle between the central aryl ring and the peripheral phenyl rings, which in turn resulted in varied degrees of planarity in the platform and hence the stacking of COF layers. A decreased dihedral angle leads to improved crystallinity and layer registry, which facilitates exciton migration within the COF plane and thereby boosts the overall photocatalytic efficiency. Furthermore, a progressive decrease in electron density in the central aryl ring of the COF platform, as the number of nitrogen atoms increase from 0 to 3, results in a more stable form with the anion radical, which enhances the charge separation, thereby increasing the probability of successful electron migration to a nearby Pt cocatalyst.Photocatalytic water splitting represents a sustainable technique of producing clean energy from water by generating hydrogen. Lotsch and co‐workers showed how COFs possess all the necessary requirements needed to serve as an ideal platform for the design of photoactive catalysts. Specifically, using a triphenylarene platform, they show that the materials' photocatalytic water reduction can be readily engineered at the molecular level.FigureThomas and co‐workers also illustrated that the tunability of COF synthesis enables a sophisticated manipulation of the performance of the resultant catalysts. Two highly porous and chemically stable acetylene (—C≡C—) and diacetylene (—C≡C—C≡C—) functionalized β‐ketoenamine COFs were synthesized, which were than applied as photocatalysts for hydrogen generation from water using Pt as a cocatalyst Figure10.44 I2 evolution rate of 390 µmol g−1 h−1, which is 7.5 times higher than that of N2‐COF (52 µmol g−1 h−1) with Pt species under identical conditions. These results give a new insight for the development of efficient photocatalytic hydrogen evolution systems.In comparison with noble metal catalysts, developing efficient photocatalytic systems for hydrogen evolution using nonprecious‐metal‐based catalysts is more desirable. Lotsch and co‐workers developed a light‐induced proton reduction catalytic process by the combination of COFs as the molecularly defined photoabsorber with an earth‐abundant molecular cocatalyst, cobaloximes, for efficient hydrogen evolution.p‐aminophenylethylene (ETTA) and benzo‐dithiophene‐2,6‐dicarboxaldehyde (BDT).Photoelectrochemical water splitting is a very attractive way to generate hydrogen using renewable energy. Bein and co‐workers first explored COFs as photoelectrodes for such applications in the absence of both cocatalyst and sacrificial agent. The COF (BDT‐ETTA) was constructed by Schiff base reactions between 1,1′,2,2′‐tetra‐FigureDeveloping a synthetic strategy to make the covalent joints both ultrastable and functional, Wang and co‐workers advanced a versatile strategy for synthesizing high performance COF‐based photocatalysts, whereby the formation of benzoxazole linkages not only stabilizes the COF structure but also decreases the optical bandgap and therefore increases the capability for visible‐light absorption. The benzoxazole‐linked COFs, LZU‐190, LZU‐191, and LZU‐192, were synthesized via the condensation of 1) 2,5‐diamino‐1,4‐benzenediol dihydrochloride with different aldehyde building blocks of 2) 1,3,5‐triformylbenzene 3) 2,4,6‐tris(4‐formylphenyl)‐1,3,5‐triazine, and 4) 1,3,6,8‐tetrakis(4‐formylphenyl)pyrene, respectively Figure11.47 D2 evolution as compared to the bulk CdS. For example, a 30‐fold augment was observed after introducing 10 wt% of the COF material during the hybrid synthesis relative to the bulk CdS.In addition to serving as a platform for introducing photocatalytically active building units, COFs can also be used as a support to immobilize photoresponsive species. For example, Banerjee and co‐workers integrated a COF with photocatalytically active CdS nanoparticles for visible‐light‐driven hydrogen production.COFs not only provide a platform for the incorporation of molecular catalysts, their ordered and customizable pore structures are promising templates for the confined growth of ultrafine metal nanoparticles. Zhang and co‐workers showed how COFs display the right combination of properties to serve as ideal host materials for size‐controlled synthesis of nanoparticles, as demonstrated by entrapping Pt and Pb nanoparticles onto a thioether‐containing COF.The development of cascade reaction processes by performing the consecutive reaction steps in one pot offered enormous economic advantages, given that costly intermediate separation and purification processes are avoided. To accomplish this, it is highly desirable to integrate different catalytically active sites within a single and recyclable material to facilitate one‐pot cascade catalysis.Considering the unique architectures and amenability of 2D COFs, they are expected to serve as an auspicious platform for integrating multiple components to bring into effect the cascade catalysis. We illustrated that a family of bifunctional COF materials can be obtained by partial metalation of a highly porous and chemically robust pyridine functionalized COF (COF‐TpPa‐Py).2 g−1, respectively. To explore the catalytic potential of these COFs, acid–base catalyzed one‐pot cascade reactions, which involve acid catalyzed hydrolysis of the acetal followed by base catalyzed Knoevenagel condensation, were chosen. Catalytic results indicated that both COFs showed high activity and recyclability.Besides catalytic species being introduced after synthesis, the intrinsic activity of COFs can also be used for cascade reactions. Qiu and co‐workers demonstrated the construction of two new 3D COFs with both acidic and basic sites, resulted from the linkages boroxine and imine, respectively, and their application in acid/base bifunctional catalysis.Figure2 with epoxides, the resultant composites exhibit significantly improved catalytic efficiency compared to individual ones. Also they clearly outperform the combination of the organic ionic compounds and the COF catalyst, a benchmark catalytic system. More importantly, the composite is stable and can be recycled for at least ten cycles with negligible loss in performance. The flexibility and movability of the catalytically active linear polymers facilitate the two types of catalytic species proximate with each other, which enables the double‐activation process. Furthermore, the locally enriched concentration of the active species in the composite catalysts results in high utilization efficiency, thereby leading to superior catalytic performance. This study is important because it affords an amenable route to bridge natural and artificial systems, given that the strategy presented herein requires neither particular types of porous materials nor linear polymers. It is also envisioned that the simple and effective method of fabrication of the composites, will promote the development of materials for a wide range of applications.The integration of multiple catalytically relevant functionalities into a single material is a concept often employed by biological catalysts and is an emerging strategy in heterogeneous and homogeneous catalysis. In an ideal scenario, the functional groups act cooperatively to enhance reactivity and/or selectivity. Nevertheless, challenges remain to design and prepare multifunctional catalysts featuring cooperative active sites, especially for heterogeneous catalysis, as the active sites spatially separated within the rigid framework are usually difficult to cooperate. We proposed a general and effective strategy for concerted heterogeneous catalysis as demonstrated by encapsulating catalytically active linear polymers within the channels of a COF bearing another type of catalytic component.2‐MIL‐68, and a COF material, which was grown on the exterior of the MOF crystals, a new type of MOF@COF core–shell hybrid material with high crystallinity and hierarchical pore structure, was synthesized.−1, which was 1.4 times that of NH2‐MIL‐68. The authors ascribed this superior performance to the increased BET surface area together with the smaller bandgap of the composite compared to the pristine NH2‐MIL‐68.The exploration of new porous hybrid materials is of great importance for designing efficient catalytic materials. Zhang and co‐workers gave the first example, by integration of a photoactive MOF, NH2‐MIL‐125(Ti) and COF‐LZU1 (Pd/TiATA@LZU1).Another example to this realm is metal doped core–shell MOFs@COFs, reported by Kim and co‐workers, as demonstrated by Pd loaded on the core–shell structure composed of NH2.3Figure−1), and can rapidly diminish the uranium concentration down to 0.1 ppb level, which is far below the U.S. Environmental Protection Agency elemental limits for hazardous wastes and even drinking water standards (30 ppb). These materials also give promise for mining uranium from seawater for nuclear fuel production, showing an uptake capacity as high as 127 mg uranium per gram of adsorbent from spiked seawater. This work thereby puts forth a promising design strategy in optimizing the performance of adsorbents for environmental remediation.The potential of nuclear events demands continuous efforts for addressing such risk.1 and 2  by Schiff base condensation reaction between tris(4‐aminophenyl)benzene (TAPB) and 2,5‐bis(methylthio)terephthalaldehyde (BMTTPA) for mercury removal from aqueous solutions.−1, 2.5 times that of COF‐LZU8.Heavy metal pollution, particularly mercury, is a persistent problem worldwide with grave public health consequences. Prompted by this critical need to mitigate heavy metal contamination and protect fresh water supplies, developing new materials for selective capture/detection of a target contaminant has long been a hot topic. 2 Figure14.60 DFigure−1 for Hg2+ and Hg0, respectively). Remarkably, COF‐S‐SH demonstrates an ultrahigh distribution coefficient value (Kd) of 2.3 × 109 mL g−1, placing it within striking distance of the all‐time mercury uptake record. This allows it to rapidly reduce the Hg2+ concentration from 5 ppm to less than 0.1 ppb, well below the acceptable limit in drinking water (2 ppb), even in the presence of a high concentration of interfering ions. Control experiments revealed that the flexibility of the chelating arms has a profound effect on the removal efficiency of the adsorbents. The highly flexible chelating arms are able to arrange in different conformations, ready for metal ions to adopt a favorable form, thereby increasing the affinity, which is reminiscent of that seen in biological systems and protein receptors. These findings suggest the merits of COFs in the design of heavy metal capture for environmental remediation. X‐ray absorption fine structure spectroscopic results revealed that each Hg is bound exclusively by two sulfur atoms via intramolecular cooperativity in COF‐S‐SH, further interpreting its excellent affinity.We also showed that 2D mesopore COFs possess all the traits to serve as a scaffold for decorating binding sites to create ideal adsorbents for toxic metal species decontamination, as illustrated by modifying sulfur derivatives on a newly designed vinyl‐functionalized mesoporous COF (COF‐V) via thiol‐ene “click” reaction Figure15.62 D3+ over Sr2+ and Fe3+.Valtchev and co‐workers reported a strategy for preparation of a 3D carboxyl‐functionalized COF (3D‐COOH‐COF) through postsynthetic modification of a hydroxyl COF, and explored it for selective extraction of lanthanide ions.The ion‐exchange process is widely applied in many industrial and household applications for purification, separation, and decontamination purposes. Qiu and co‐workers demonstrated the synthesis of two new 3D ionic COFs and their potential application for the removal of hazardous ions. The COF materials were obtained by the condensation of tetrakis(4‐formylphenyl)methane with diimidium bromide or ethidium bromide (EB), named as 3D‐ionic‐COF‐1 and 3D‐ionic‐COF‐2, respectively.2 capture. Sorption tests revealed that these materials not only could efficiently remove I2 from solution, but also I2 vapor.Trabolsi and co‐workers reported for the first time the use of the Zincke reaction to fabricate a viologen‐linked covalent organic network with controllable morphology by varying the polymerization conditions, as demonstrated by the reaction between 1,1′‐bis‐‐1,1′‐diium dichloride and TAPB.2)2, reported by Banerjee and co‐workers.2)2 were first reduced to the primary amines followed up by an aminolysis reaction of acetic anhydride to form an amide bond to yield TpBD(NH2)2 and TpBD(NHCOCH3)2, respectively. To show the influence of functionalities on the removal efficiency, adsorptive removal of lactic acid was studied, given that it is a major precursor for biodegradable plastics. A great increase in affinity of the framework for lactic acid upon reduction of the nitro group to the amine was observed, giving uptake capacities of 2.5 and 6.6 wt%, respectively.Organic micropollutants are emerging contaminants in global freshwater supplies. These compounds cannot be removed effectively by wastewater treatment plants, and their negative effects on the environment and human health are now coming into focus. The development of new materials to help combat this emerging global problem is urgent. The high chemical stability of β‐ketoenamine COFs in a wide range of chemical conditions allows for the multistep postsynthetic modification to impart them with new properties while retaining the pore structure of the pristine COF material. These features suggest COFs of this type to be promising candidates for selective adsorption processes. Bein and co‐workers presented the first demonstration of a two‐step postsynthetic modification in a β‐ketoenamine COF,2 g−1 was obtained (PyTTA‐BFBIm‐iCOF).−1, which was the highest among adsorbent materials reported at that time.Given that numerous dye molecules are charged, using electrostatic interaction is an alternative for their removal. To create such interfaces, Jiang and co‐workers rationally designed an ionic building unit, 5,6‐bis(4‐formylbenzyl)‐1,3‐dimethyl‐benzimidazolium bromide (BFBIm). By condensation of BFBIm and PyTTA, a cationic COF material with a BET surface of 1532 m2 g−1 with a narrow pore size centered at 1.43 nm. Interestingly, SA‐COF exhibits reversible proton tautomerism triggered by adsorption and desorption of water molecules. Given the ordered pore channel and multifunctional groups, SA‐COF was then explored as a versatile adsorbent for water soluble organic pollutant separation. It was found that SA‐COF showed obvious size‐dependent adsorption, as demonstrated that its binding affinity toward dye molecules declined with an increase in molecular size and could completely exclude molecules with dimensions larger than the pore size. In addition to this, the —OH and —NH moieties in SA‐COF can be deprotonated or protonated in basic or acidic conditions, respectively, showing a pH‐controllable ionicity. By virtue of this, SA‐COF can efficiently separate charged molecules. Furthermore, given the basicity of the N—H moiety in the trans‐keto form, SA‐COF can discriminate functional groups with different acidities, and it selectively bonded —OH over —NH2 groups under neutral conditions.The tunable functionality of the pore surface of COFs together with their ordered pore channels can be exploited for the separation of molecules according to the combined contribution of size, charge, and functionality. To demonstrate this, Loh and co‐workers designed a salicylideneanilines‐based COF material (SA‐COF) by condensation of 1,3,5‐tris(4‐aminophenyl)benzene and TFP.FigureP/P0 up to 0.9 (less than 10 mg g−1), whereas it has a toluene uptake capacity exceeding 680 mg g−1 at P/P0 = 0.88. These results indicate that COF‐VF offers exceptional abilities to overcome the problems associated with the adsorption of harmful volatile organic compounds in humid environments. To add their applicability in the real world, experiments were designed to integrate them with substrates to increase their processability. We integrated COF‐VF with melamine foam and the resultant COF‐VF@foam shows highly efficient absorption of not only petroleum products, but also toxic solvents, such as chloroform and nitrobenzene, with an uptake capacity up to 142 times its own weight. Remarkably, the oil absorption kinetics of COF‐VF@foam was very rapid, reaching its saturated absorption capacity within 5 s with the captured oil readily removed by simple squeezing of the foam and the recovered COF‐VF@foam was reused without any loss in its performance, requiring no further treatment, thus suggesting that COF‐VF@foam is a promising candidate as a “suction skimmer.”Pollution by crude oil, petroleum products, and toxic organic solvents, which results in severe environmental and ecological problems, is a risk of growing concern. Worthy of note, oil spill cleanups amount to over 10 billion dollars annually. Remediation of these environmental issues involves the use of large amounts of adsorbents such as sand, activated carbons, or zeolites. However, the effectiveness of such adsorbents is often compromised by their affinity for moisture.Figure−2 h−1 bar−1, which is 2.5‐fold higher than the existing polyamidenanofilmbased membranes based crosslinked polymers.s Figure b. Due toi Figure c. Given 2.4p‐aminophenyl)methane and 1,3,6,8‐tetrakis(4‐formylphenyl) pyrene with a BET surface of 1290 m2 g−1 and microporosity centered at 0.59 nm. Due to the isolated imine‐functionalized pyrene units in the 3D network, 3D‐Py‐COF showed an intense yellow green luminescence, which was further explored for explosive detection. Using picric acid (PA) as the model, fluorescence of 3D‐Py‐COF was gradually quenched along with PA concentration increased in the suspension. A 75% quenching degree can be reached when the concentration of PA is 20 ppm, indicative of its high sensitivity to PA.Given that COFs show good photophysical properties, one might predict that they would act as efficient chemical sensors. Wang and co‐workers reported a newly designed 3D pyrene‐based fluorescent COF (3D‐Py‐COF) with a twofold interpenetrated pts topology.To address the concerns of the moderate electron delocalization and hydrolytic stability of imine‐linked COFs, which may impede their real application, Perepichka and co‐workers developed a new dynamic polymerization based on Michael addition‐elimination reactions of β‐ketoenols with amines for the preparation of COF materials.m)] analyte concentration, thereby showing potential for explosion chemical detection. Very interestingly, TfpBDH‐CONs exhibit a “turn‐off” detection in the dispersion state, but conversely exhibit a superior “turn‐on” detection capability for 2,4,6‐trinitrophenol in the solid state, promising for its application in visual detection of nitroaromatic compounds.In many cases, due to the aggregated π‐stacked layers that resulted in luminescence concentration quenching and ineffective interaction with analytes, the bulk 2D COFs exhibit only moderate chemical sensing ability. To address these challenges, Baneriee and co‐workers exfoliated the bulk COF (TfpBDH) synthesized from 1,3,5‐tris(4‐formylphenyl)benzene (Tfp) and pyromellitic‐N,N′‐bisaminoimide (BDH), to produce covalent organic nanosheets (CONs) by the liquid phase exfoliation method.FigureNot limited to small molecules, the covalent organic nanosheets can also be used as a novel sensing platform for DNA detection. Zhang and co‐workers showcased the first example with this respect.2.5Porous materials, such as mesoporous silica materials or MOFs, have long been studied and shown promise in drug delivery applications. Given their adjustable pores, excellent stability, and tunable compositions, COFs are expected to be effective materials for drug delivery. To show a proof‐of‐concept study for drug delivery applications, two new 3D COFs constructed by imidization between pyromellitic dianhydride and TAA or tetra(4‐aminophenyl)methane were rationally designed and named as PI‐COF‐4 and PI‐COF‐5, respectively.To realize a targeted drug delivery system and to increase the biocompatibility, Banerjee and co‐workers developed a promising strategy based on scalable salt‐mediated synthesis of COFs and subsequent functionality based sequential postsynthetic modifications to yield targeted materials.FigureAchieving better control of drug delivery requires knowledge of the interactions between the immobilized drug and its host material. Using a variety of spectroscopy techniques, Lotsch and co‐workers beautifully illustrated that the free electron pairs on the imine nitrogens of the COF are the main contributors for anchoring the guest molecules reversibly by H‐bonding interactions.2 g−1 and narrow pore size distribution centered at 3.7 nm as well as excellent stability in a wide range of conditions including a phosphate buffer, a medium often used for enzyme loading. Considering the size constraints of the COF, trypsin with hydrodynamic size of around 3.8 nm was chosen for their studies. Successful immobilization of trypsin was verified by confocal laser scanning microscopy, revealing that most of the trypsin was immobilized in the mesoporous walls of the hollow spheres, given the fact that the hollow cavity of the sphere is nonfluorescent. Enzymatic assay revealed that around 60% of the activity of the free enzyme was retained after immobilization in the hydrolysis of N‐benzoyl‐L‐arginine‐4‐nitroanilide to p‐nitroaniline. Although the stability of the immobilized enzyme, such as tolerance to non‐natural conditions as well as recyclability, was not investigated, this work implies that COFs hold great promise for enzyme immobilization. This is expected to spur further endeavors on this aspect.Coupling enzymes with solid supports affords a unique opportunity to shield them from deactivation, provides potential for recyclability, and increases the operational stability. Banerjee and co‐workers showed the first case of using COFs for enzyme encapsulation.FigureWe have demonstrated, that due to the unique mesoporous structure and the tunable surface chemistry, COFs provided both high affinity for enzyme loading and a favored microenvironment that enhanced the enzymatic performance better than in other types of porous materials reported, as demonstrated by Lipase PS, a versatile type of enzyme Figure20.82 T2.62.6.1A distinctive aspect of 2D COFs is their long‐range π‐orbital overlap in the stacking direction, which facilitates charge carrier transport through the preorganized π‐pathways as well as gives rise to high exciton‐ and charge‐mobilities of interest for optoelectronic devices. The stacked π‐systems found in 2D COFs adopt an eclipsed fashion, facilitating their orbital interactions as well as providing aligned conduction pathways. In addition, their pores run parallel to the stacking direction, providing an opportunity to introduce complementary semiconductors. The resultant vertically aligned p–n junctions embody a morphology long thought to be ideal for photovoltaic performance. Moreover, unlike polymeric semiconductors, COFs generally show excellent thermal stability and do not undergo thermal phase transitions, which frequently require thermal or solvent annealing to attain morphologies suitable for reasonable photovoltaic performance.Jiang and co‐workers reported the first photoconductive COF  synthesized by self‐condensation of 2,7‐pyrene diboronic acid.To improve the photoconductive performance, the crystallization of electron donors and acceptors into macroscopic heterojunctions with segregated donor and acceptor domain structures is highly pursued. 2D COFs provide an exceptional platform for precise control of the structure and its properties sincethe building blocks in 2D COFs are arranged in a perfect grid of repeating hexagons. In this context, Jiang and co‐workers demonstrated the first COF material that integrated donors and acceptors by cocrystallization of the building units bearing these moieties, as exemplified by triphenylene donor and benzothiadiazole acceptor.61‐butyric acid methyl ester (PCBM), TT‐COF was soaked in a PCBM chlorobenzene solution. The resultant composite exhibited a significant photoresponse as well as supports efficient charge transfer within the lifetime of the excitons.As an alternative, Bein and co‐workers proposed a supramolecular approach by spatially confining electron acceptors within the open channels of electron‐donating frameworks.Figure8) as vertices and 1,4‐phenylenediboronic acid (BDBA) and 2,5‐bis(azidomethyl)‐1,4‐phenylenediboronic acid (N3‐BDBA) at different molar ratios as edges under solvothermal conditions for the synthesis of a series of electron‐donating intermediate ZnPc‐COFs with adjustable contents of the azide units on the channel walls  for further covalently anchoring C60. To show their potential application in photoenergy conversion, photoinduced electron transfer and charge separation were studied by means of time‐resolved electron spin resonance spectroscopy. It was revealed that the lifetime of the composites was governed by the delocalization of radical cations in the ZnPc columns, whereas the radical anions were localized at C60, thereby suggesting the cooperation between the COF skeleton and C60 anchored.Although this pore infiltration strategy is feasible, it encounters a problem with the fullerene elution from the channels. To tackle this concern, Jiang and co‐workers provided an alternative way toward organizing donors and acceptors into an ordered system, whereby the guest molecules were covalently anchored on the ordered pore channels Figure21.87 T2.6.23 hybridized boron anionic centers that were connected by transesterification of four diol groups in a D4‐symmetric macrocycle 5 and trimethyl borate by formation of spiroborate linkages + and Li+ were synthesized and named as ICOF‐1 and ICOF‐2, respectively. N2 sorption isotherms collected at 77 K revealed that both of them are microporous materials with BET surface areas of 1022 and 1259 m2 g−1 for ICOF‐1 and ICOF‐2, respectively. However, due to the low quality and the complex PXRD data, the simulated crystal packing was not provided. Given the high content of accessible Li ions, ICOFs were thus explored as a Li‐conducting solid electrolyte. Advantageously being lightweight and possessing high thermal and chemical stability, a room‐temperature conductivity of 3.05 × 10−5 S cm−1 was observed. More interesting, being different to classic polymer electrolytes, which show nonlinear activation energy at higher temperatures, ICOF‐2 exhibits a linear characteristic of conductivity with temperature, reminiscent of ceramic solid conductors. The activation energy of ICOF‐2 was calculated to be 0.24 eV per atom, superior to those for typical solid‐state polymer electrolytes and even comparable to some of the state‐of‐the‐art crystalline solid electrolytes.Zhang and co‐workers reported the first example of ionic covalent organic frameworks (ICOFs) with spes Figure22.88 TFigure+ hold great promise as a solid‐state electrolyte material with a high Li ion conductivity of up to 2.7 mS cm−1 at 30 °C and excellent long‐term Li ion stripping/plating stability.Using cyclodextrin (CD) as the soft struts, Feng and co‐workers reported the construction of a 3D ionic COF through the reactions between γ‐CD and trimethyl borate, with the units joined via tetrakis(spiroborate) tetrahedra with various counter ions  was synthesized by condensation of 1,3,5‐tri(4‐aminophenyl)benzene (TPB) with 2,5‐bis((2‐methoxyethoxy)methoxy)terephthalaldehyde (BMTP), followed by treatment with LiClO4 solution. The flexible oligo(ethylene oxide) chains on the channel walls facilitate the dissociation of the ionic bond of lithium salts upon complexation with lithium ions, thereby offering a pathway for ion conduction and promoting the ion transport through a low energy‐barrier vehicle mechanism. As a result, the ion conductivity was greatly enhanced by more than 3 orders of magnitude relative to that of ions across the bare nanochannels.Poly(ethylene oxide)‐based electrolytes have been heralded as promising materials for lithium ion batteries. However, as liquid electrolytes they also face issues such as leaking and safety. To solve these concerns encountered, the development of solid‐state polyelectrolytes is promising.2.6.33PO4 and 4‐aminoazobenzene in which H3PO4 is anchored on the azo (—N=N—) center by protonation, whereas the H2PO4‐anions are stabilized via H‐bonds. With these in mind, Banerjee and co‐workers synthesized an azo (—N=N—)‐functionalized COF (Tp‐Azo COF) by condensation of triformylphloroglucinol (Tp) and 4,4′‐azodianiline (Azo). After proving its stability against acid, a simple impregnation process was carried out to infiltrate phosphoric acid into the framework with an uptake capacity of 5.4 wt% (PA@TpAzo). Impressively, PA@TpAzo exhibited a great proton conductivity of 6.7 × 10−5 S cm−1 under anhydrous conditions. The azo units of Tp‐Azo COF were protonated and formed hydrogen‐bonding interactions with the H2PO4− anion, which further interacted with free phosphoric acid molecules to form a hydrogen‐bonding network in the 1D channels, enabling the occurrence of self‐dissociation. The proton conductivity reached 9.9 × 10−4 S cm−1 under 98% relative humidity. These results imply that COFs offer an appealing platform for the construction of proton‐conducting systems for applications in fuel cells.The utilization of COFs in proton conduction had been impeded by their stability.3 S cm−1 at 130 °C, which is two orders of magnitude higher that of the state‐of‐the‐art imidazole‐loaded MOF.Given the 1D, ordered, mesoporous channels, and ultrastability of TPB‐DMTP‐COF, it is envisioned to enable a high loading of proton carriers and thereby improved proton conductivity. To use these advantages, Jiang and co‐workers employed this COF as a host material for loading proton carriers and imidazole and triazole were chosen as representative N‐heterocyclic proton carriers, yielding im@TPB‐DMTP‐COF and trz@TPBDMTP‐COF, respectively.12O403− and then investigated its performance in proton conduction.12) was obtained by combination of a cationic monomer, ethidium bromide (EB), with 1,3,5‐triformylphloroglucinol (EB‐COF:Br), followed by ion exchange with H3PW12O40 , which is two orders of magnitude higher than that of EB‐COF:Br. Under otherwise identical conditions, the physical mixture of H3PW12O40 and EB‐COF:Br only gave a value of 3.2 × 10−5 S cm−1. These results indicate the type and the dispersion degree of anions greatly affect the materials' proton conductive performance. It is worth mentioning that this is one of the best COF‐based proton conducting materials reported thus far.Although, polyoxometalates show high performance in proton conduction, their high solubility represents a major hurdle that prevents them from real applications. To address this issue, Zhu and co‐workers developed a cationic COF to immobilize PW2.6.42Q/Q electrochemistry, it is envisioned that this chemistry could be incorporated in the COF backbone. Dichtel and co‐workers incorporated redox‐active 2,6‐diaminoanthraquinone (DAAQ) moieties into a 2D COF linked by β‐ketoenamines to confer outstanding hydrolytic stability.Figure2D COFs featuring ordered π‐columns and open nanochannels make them a promising candidate to be designed as energy storage materials. Excited by the fascinating H2 carbon‐conjugated COF material by designing a C=C bond formation reaction.m NaOH aqueous solution, the reactions were reversible, providing the self‐correction needed to form a crystalline material. Due to the extended π‐conjugated structure, the resultant COF is a semiconductor with a discrete bandgap of 1.9 eV. Nonetheless, its properties can be readily tailored. Chemical oxidation of this material with I2 greatly enhanced its conductivity, and the generated radicals confined on the pyrene centers imparted a high spin density and paramagnetism.To improve the electrical conductivity, Jiang and co‐workers provided an alternative strategy. Stimulated by the excellent conductivity of 2D fully conjugated networks of graphene and related materials. They pioneered a topology‐directed reticular construction of crystalline spX%‐NiP‐COF . The free radical species, as exemplified by oxyl (TEMPO), were then grafted by the click reaction. Obvious redox peaks were detected by cyclic voltammetry (CV) for the COFs containing the TEMPO moiety, whereas the pristine COFs did not show any reduction–oxidation response. These positive effects clearly confirmed the effectiveness of channel‐wall functionalization in introducing redox activity. According to the CV profiles, it was revealed that the output currents of these samples were augmented along with the density of the TEMPO functionality.Using COFs as a designer platform, Jiang and co‐workers synthesized a series of redox‐active COFs for efficient energy storage by postsynthetic channel‐wall modification with free radical species.33.1Unlike MOFs and supramolecular networks which are held together by bonds weak enough to be broken readily under their assembly conditions, allowing for rapid error correction and thereby permitting the growth of large single crystals, the vast majority of COFs reported thus far are produced as microcrystalline powders. Therefore, their structures are assigned by comparing the refined PXRD pattern with simulated patterns of eclipsed and staggered stacking arrangements, leading to controversy. Generally, it is well recognized that various kinds of out‐of‐plane disorder, such as random or poorly defined stacking sequences, and in‐plane defects, are prevalent.[[qv: 9k]] However, these offsets could hardly be confirmed experimentally for a long while, because peak broadening in powder samples is too large to differentiate between eclipsed and slightly offset structures. Previously, computational studies reveal that 2D COFs do not typically crystallize into fully eclipsed cofacial packing, as suggested by the simulated structure.2 gas adsorption isotherms and powder X‐ray diffraction, respectively.As shown above, even low quality COFs have shown preliminary promise for catalysis, water purification, storing electricity, and many more. Once developed further, higher‐quality samples of these materials will enable these applications to be explored more fully. Synthesizing single‐crystal COFs represents a longstanding challenge in material science. Previous attempts to make single crystalline COFs have been thwarted, in part because the formation of bonds between subunits is essentially irreversible, whereby crystallization cannot easily be tamed. This dilemma had not been over crossed until 2013, Wuest and co‐workers successfully isolated high quality covalent organic networks by nitroso self‐addition, allowing structures of the resultant materials to be determined in detail by single‐crystal X‐ray diffraction.FigureVery recently, a general procedure to grow large single crystals of 3D imine‐based COFs was developed Figure26.102 FigureNevertheless, the above developed two strategies were not generalized to 2D COFs. Almost at the same time as the publication of the 3D imine‐based COFs, Dichtel and co‐workers reported boronate ester‐linked 2D COFs isolated as discrete particles comprised of single crystalline domains with sizes ranging from 500 nm to 1.5 µm Figure27.103 3.2COFs are typically synthesized as powders under solvothermal conditions. The limited utility of these forms precludes many applications for COFs. For example, 2D COFs incorporate functional p‐electron systems into ordered structures ideally suited for optoelectronic devices. However, as unprocessable powders, these materials cannot be interfaced reliably to electrodes or incorporated into devices to harness or even quantify these properties. COF films offer an extraordinary opportunity to organize and orient functional p‐electron systems into robust periodic structures predictably through chemical synthesis. The growth of thin COF films with control over the film thickness, morphology, and crystallinity is highly desirable for the utilization of COFs in diverse applications. Dichtel and co‐workers introduced the first oriented 2D layered COF films, as demonstrated by COF‐5 and a Ni phthalocyanine‐1,4‐phenylenebis(boronic acid) (PBBA) COF, on substrate‐supported single layer graphene (SLG).However, considering that the above methods employed for growing thin COF films are based on reactive precursor solutions under solvothermal conditions, COFs were formed as both an insoluble powder and as a continuous film on the substrate surface, challenges such as scalability, yield, and morphology control still remain. Alternative synthetic routes to form COFs are highly desirable. Bein and co‐workers ingeniously translate the concept of steam‐assisted conversion to the synthesis of a series of 2D COF films at room temperature.In addition to growing thin films, a surface deposition strategy has also been used for integrating COFs with other substrates to extend their application. For example, Yan and co‐workers applied a chiral COF based on tartaric acid as stationary phases for chiral separation, which were in situ integrated with substrates to synthesize chiral COF‐bound capillary columns.Considering that it is uncommon for a material to be usable in applications as synthesized, they are typically processed into a specific form, such as a pellet, a thin polymer membrane, or a surface deposited film. Processability is therefore an important functional property that is often ignored, at least in the early discovery phase for a new material. Simple, scalable, and controllable processing routes with few steps are therefore desirable, irrespective of material type.3.32O is available to maintain reversible conditions, allowing for an increased solubility of the precursors and improved kinetics as well as structures for self‐correction. Although the solvothermal synthesis pathway in many cases leads to satisfactory results in terms of quality of the products, it also has some weaknesses. The most important could be the difficult transferability to industrial applications, as scale‐up is challenging and the reaction rates observed in many COF syntheses are very slow . The search for alternative green, safe, and efficient technologies is one of the priorities in current scientific research. With this objective, some promising synthetic approaches were developed.To have an impact on real applications, porous materials must be scalable. The first COF synthesis was performed under solvothermal reaction conditions, and this method to date is still the most often applied approach for COF formation. Thereby, the COF precursors are placed in a pyrex tube together with the desired solvent or solvent mixture and catalysts or modulators and then the tube is flash frozen at 77 K, evacuated, and flame‐sealed. The reaction mixture in these tubes can be heated above the normal boiling point of the solvent and the closed system also ensures that H3.3.1Cooper and co‐workers showed that microwave synthesis could offer a highly convenient method for the rapid production of COFs, as demonstrated by COF‐5 and COF‐102.3.3.22 g−1.For some β‐ketoenamine COFs, mechanical grinding of the COF building units was found to yield the same COF structures as that known from solvothermal reactions. However, the synthesized COFs were less crystalline compared to the solvothermally synthesized batches and processed rather low BET surface areas of below 100 m3.3.3p‐toluenesulfonic acid and subsequent addition of 1,3,5‐triformylphloroglucinol (Tp) and water, the ketoenamine COFs were obtained in high quality (BET surface area up to 3100 m2 g−1) after heating to 170 °C for 1 min. This strategy overcomes the long‐term synthetic hurdles of solvothermal synthesis as well as low surface area of the resultant COFs encountered by “solid‐state conversion.” Interestingly, the ground mixture had the consistency of dough and could be processed into various shapes without any additional binder, hence enabling the fabrication of COF sculptures via this “terracotta process” (FigureTo increase the surface area and crystallinity of “solid‐state conversion,” Banerjee and co‐workers developed a liquid‐assisted grinding method, where a catalytic amount of liquid was introduced to the COF precursors during grinding.s” Figure28.3.3.42 g−1 can be achieved within 10 min.Dichtel and co‐workers developed a metal‐triflate catalyzed room temperature synthesis of imine COFs that led to COFs with BET surface areas superior to the solvothermally synthesized frameworks. High quality COF materials with BET surface areas up to 2175 m3.3.5This synthetic pathway was developed by Bein and co‐workers and the corresponding work has been introduced previously as ref. 3.3.6−3 day−1.Zhao and co‐workers pioneered the room temperature continuous flow synthesis of COFs exemplified by COF‐LZU1, with an extremely high space‐time yield of 703 kg mCOFs have shown preliminary promise for catalysis, environmental remediation, energy storage, and many more. Although progress has been made, this field of research is still in its infancy. Looking forward, a future direction would be to fully make use of construction principles for COFs to precisely integrate building blocks to achieve predesigned compositions, components, and functions. To find greater use at an industrial scale, COFs must be scalable and must satisfy multiple functional criteria such as long‐term stability, high performance, and processability, all within a viable cost envelope.The authors declare no conflict of interest.


R=0.072) and perceived individual discrimination (R=0.059). DISCUSSION/SIGNIFICANCE OF IMPACT: Allostatic load appears to be high in individuals who self-report exposure to violence. Both perceived mental health and violence were correlated to elevated stress biomarkers. When Epstein-Barr virus viral capsid antigen IgM was compared with violence features characterized in the data set, we found that internalization of environmental stressors were most strongly correlated to elevated allostatic load markers. This work suggests that internalization of experienced violence may be as important as the actual violence experience.OBJECTIVES/SPECIFIC AIMS: Allostatic load, the chronic stress-induced wear and tear on the body, has a cumulative deleterious effect in individuals over their lifetime. Recent studies have suggested that socio-economic status, psychological determinants, and biomedical health cumulatively contribute to allostatic load in young adults. Although these finding individually suggest that African American children may be particularly susceptible to the effects of allostatic loading due to racially-based discrimination and economic instability, few studies have shown the effect of exposure to violence on the allostatic load carried by young African Americans. METHODS/STUDY POPULATION: The Biological and Social Correlates of Drug Use in African American Emerging Adults (BADU) data set is composed of young African Americans  living in the Washington, DC area, collected from 2010 to 2012. Study participants were sought equally between males and females . This data set provides a rich source of information on the behavioral, mental, and physical health of African American young adults (18–25 year olds) living in the Washington, DC area. Analysis of 6 biomedical markers were measured in BADU study participants: C-reactive protein, cortisol, Epstein-Barr virus IgG, IgE, IgA, and IgM, known to be markers of immune stress and allostatic load. Naive Bayes was used to identify participant responses that were correlated to elevated stress biomarker levels. RESULTS/ANTICIPATED RESULTS: Violence was most closely correlated to elevated EBVVCA IgM and IgE levels. Elevated IgE levels correlated to increased experience of familial violence and sexual abuse; familial drug abuse and depression; violence and community violence. Cortisol is positively correlated to reported emotional state (