In biological systems, coordinatively saturated heme proteins constitute the redox cofactors of the cytochrome-based electron shuttles. In this regard, metalloporphyrins are electrochemically well-studied systems owing to their unique d-electron configurations relative to the porphyrin macrocycle core 79,80 . Morris and co-workers have prepared CoPIZA/FTO by growing the CoPIZA MOF from TCPP(Co III ) linker and Co II -carboxylate node on the fluorine-doped tin oxide (FTO) electrode 81 . These films showed catalytic activity for carbon tetrachloride reduction. Interestingly, electrochemical impedance spectroscopic **data** collected for these MOF-modified electrodes revealed a conductivity of 3.62 × 10 −8 S cm −1 -a behavior that may have been augmented by the redox contribution from both the struts and Co nodes. Cyclic voltammogram (CV) of CoPIZA (@FTO) evinced two reversible cathodic peaks at −1.1 and −1.45 V (vs ferrocyanide) corresponding to TCPP(Co III/II ) and TCPP(Co II/I ), respectively. Interestingly, Co III SBU shows similar redox potential values at −0.87 and −1.39 V corresponding to Co III/II and Co II/I redox processes, respectively. The current density and the cathodic-anodic peak separation of these redox events were found to be scan-rate dependent, and therefore, the charge transport rate (k CT ) in this diffusion-limited process can be expressed in terms of the diffusion coefficient (D hop~7 .55 × 10 -14 cm 2 s −1 ). Hod's group reported tuning redox conductivity by engineering the defect site density with iron porphyrin ligands in a UiO-66 type MOF 82 . The Zr nodes with varying degrees of missing linker (and the corresponding void space) were used to install Fe-porphyrin (Hemin) molecules via SALI. These hemindecorated UiO-66 MOFs were used to probe the hopping rate as a function of porphyrin loading (i.e., originally the defect density) that defines the variable (average) Fe-Fe distances. Transient electrochemical **data** revealed that the higher hemin-loaded (i.e., a shorter d Fe-Fe ) samples manifest a low diffusion rate and the maximum diffusion rate was obtained for relatively lower heminloaded samples. Considering microporous UiO-66 system, a highly defective sample that led to high hemin loading allowed the decoration deep within MOF crystal, which seemed to impede the mass transport of the counterions. Whereas, in low-defect samples, the hemins mostly reside at the surface and therefore suppress the mass transport-related issues.