Highly Luminescent Ln MOFs Based on 1,3 Adamantanediacetic Acid as Bifunctional Sensor
Abstract A series of lanthanide metal organic frameworks (Ln MOFs) are synthesized under mild hydrothermal condition by introducing the ligand of 1,3 adamantanediacetic acid (H2ADA) They are three dimentional (3D) structures and have the formula of [Ln(ADA)1.5(phen)]n (Ln3+ Eu3+ 1a, Gd3+ 1b, Tb3+ 1c, La3+ 1d, Ce3+ 1e, Pr3+ 1f, Nd3+ 1 g, Y3+ 1 h; phen 1,10 phenanthroline) These Ln MOFs are fully characterized by single crystal X ray diffraction, PXRD, TGA, EA and FT IR. Luminescence properties, including luminescence spectra, luminescence decay lifetimes and luminescence quantum yields (QYs) are analyzed in detail. Eu3+ complex of 1a shows highly luminescence QYs of 58.61% which due to that the triplet state of phen competes well with the excited emission state of Eu3+ Further investigation reveals that 1a is a bifunctional sensor, which can be used as a turn off luminescence sensor for detecting Ni2+ and turn on luminescence sensor for probing Val at the same time. Interestingly, the limit of detect (LOD) for sensing Ni2+ is an ultrahigh sensitive value of 1.0 x 10 9 M (5.9 x 10 5 mg/L) which is lower than the Chinese environmental quality standard (0.5 mg/L of total Ni2+ content, GB25467 2010) and it is the most sensitive chemosensor for detecting Ni2+ to the best of our knowledge. Investigation also reveals there is a good linear relationship between luminescence intensity and the concentration of Ni2+ in 0.2 0.6 mM. The sensing mechanism for detecting Ni2+ and Val are also discussed.