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

Abstract

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 π⋯π 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.