A stable 2D luminescent metal–organic framework as a highly sensitive sensor for Fe3+ and Cr2O72−/CrO42− in water

Abstract

Reacting N,N′-bis(3,5-dicarboxyphenyl)oxalamide (H₄BDPO) with d¹⁰ electronic configuration Cd²⁺ ions under solvothermal conditions produces a two-dimensional (2D) metal–organic framework (MOF), {[Cd₃(HBDPO)₂(H₂O)₇]·4H₂O}_n (1), which has been further characterized by different methods, including X-ray single-crystal diffraction, elemental analysis, infrared (IR) spectroscopy, thermogravimetric (TG) analysis and powder X-ray diffraction (PXRD). The structural analyses of 1 indicate that two crystallographically independent Cd²⁺ ions are interconnected by partly deprotonated HBDPO³⁻ ligands to generate a 2D (3,4)-connected topological layer, and the adjacent layers are further formed in a 3D supramolecular structure by hydrogen bonding and π⋯π stacking interactions. Luminescent results show that 1 can serve as a luminescent sensor for sensitively detecting Fe³⁺ and Cr₂O₇²⁻/CrO₄²⁻ ions based on the fluorescence quenching effect. More importantly, the high stability of 1 makes it suitable for the detection of Fe³⁺ and Cr₂O₇²⁻/CrO₄²⁻ ions in the natural water system.