Water-stable Eu-MOF fluorescent sensors for trivalent metal ions and nitrobenzene.

Two novel Eu metal-organic frameworks (MOFs), namely {[Eu2(pdba)3(H2O)3]·2H2O}n (1) and {[Eu3(pdba)4(H2O)4]·5H2O}n (2), were prepared with 4'-(1H-pyrazol-3-yl)-[1,1'-biphenyl]-3,5-dicarboxylic acid (H2pdba) under hydrothermal conditions. MOF 1 exhibits a 3D supramolecular structure assembled from the ππ interactions between the benzene rings of the ligands, whereas 2 comprises a 3D structure through coordination connection between nitrogen atom and Eu3+. It is worth noting that the two MOFs showed good luminescence performance and high-sensitivity fluorescence quenching behavior toward Fe3+ (Cr3+) and nitrobenzene. Furthermore, the experimental results for stability in water and cycle test show that these two MOFs can be used as potential fluorescent probes.