Two lanthanide metal–organic frameworks as sensitive luminescent sensors for the detection of Cr2+ and Cr2O72− in aqueous solutions

Abstract

Two lanthanide–organic frameworks [Ln(HPIDC)(m-bdc)·1.5H₂O]_n (Ln = Eu 1 or Tb 2; H₃PIDC = 2-(4-pyridyl)-1H-imidazole-4,5-dicarboxylic acid; m-H₂bdc = 1,3-benzenedicarboxylic acid) were synthesized under hydrothermal conditions. Compounds 1 and 2 are all of a 3D 6-connected pcu topology. There are uncoordinated nitrogen atoms in the molecule, indicating that the uncoordinated pyridine groups and imidazole groups can serve as functional groups. We tested their luminescence detection ability for cations and anions. Fluorescence measurements show that two compounds (1 and 2) can detect Cr²⁺ ions and Cr₂O₇²⁻ anions with high selectivity and sensitivity, which suggests that the two Ln-MOFs are promising functional luminescent sensor materials for sensing metal ions and anions.