Two unique 2D metal-organic frameworks based on various metal-oxygen chains for high sensitivity sensing of Fe(III) and Cr(VI) in aqueous media

Two new 2D MOFs, namely, {[Cd2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (1), {[Co2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (2) were constructed under the solvothermal conditions by using 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid and d10 metal ion Cd(Ⅱ) and Co(Ⅱ). Because the diversity of ligands leads to two different coordination patterns in complexes 1–2, resulting in 1 and 2 with multiple structures. Both 1 and 2 exhibit a 3D supramolecular framework, which based on different metal-oxygen chains. The chains form a 2D layered structure through the carboxyl oxygen atoms in the ligand. The solid-state luminescence spectra of 1 at room temperature showed that the maximum emission peak is 458 nm (λex = 346 nm). At the same time, 1 showed high fluorescence selectivity and low detection limit for Fe3+ cations, Cr2O72− and CrO42− anions in aqueous solution, and can be used as a potential multifunctional material for the detection of these substances. In addition, the fluorescence sensing properties and quenching mechanism of the above ions are discussed in detail.