Lanthanide-MOFs as multi-responsive photoluminescence sensor for sensitively detecting Fe³⁺, Cr₂O₇^2- and nitrofuran antibiotics?

Fast and selective detection of contaminants plays a key role in meeting human health and environmental concerns. Herein, two groups of isostructural lanthanide MOFs, [Ln(Hpta)(oxalic acid)].H2O (1-Eu, 2-Gd) and [Ln(pta)(oxalic acid)(0.5)(H2O)(2)].2H(2)O (3-Eu, 4-Gd) (H(2)pta = 2-(4-pyridyl)-terephthalic acid, C2O4- = oxalic acid), were synthesized by solvothermal method. Single crystal X-ray diffraction reveals that 1 and 2 are 3D neutral frameworks, while 3 and 4 consist of 2D layers with parallelogram holes and stack into 3D networks through O-H...N and O-H...O hydrogen bonding interactions. All complexes remain crystalline and stable below 400 degrees C, suggesting preeminent thermostability. Noteworthily, only 3 shows excellent chemical stability in water and organic solvent. Therefore, the solid-state fluorescence spectrum was used to characterize 3 which exhibited intense red luminescence. The N active sites in the pore channels of 3 are conducive to displaying a distinct quenching effect for Fe3+ cations in aqueous solutions, Cr2O72- anions in DMF and DMA solutions, and nitrofuran antibiotics in the DMF solvent. Overall, 3 is a prospective luminescent sensor for detecting Fe3+, Cr2O72- and nitrofuran antibiotics.