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

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]·2H₂O (3-Eu, 4-Gd) (H₂pta = 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 °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, Cr₂O₇^2- anions in DMF and DMA solutions, and nitrofuran antibiotics in the DMF solvent. Overall, 3 is a prospective luminescent sensor for detecting Fe³⁺, Cr₂O₇^2- and nitrofuran antibiotics.