A novel porous Zn-MOF based on binuclear metal clusters for fluorescence detection of Cr(VI) and adsorption of dyes

A novel Zn-MOF: {[Zn₃(L)₂(H₂O)₄]·(H₂O)₃·(CH₃CN)₃}_n was synthesized from tricarboxylate pyridine ligand 3-(2,4-dicarboxyphenyl) -4-carboxypyridine (H₃ L) under solvothermal conditions. Zn-MOF was a three-dimensional porous framework composed of binuclear metal cluster [Zn₂(COO)₃ N] and a variety of metal oxygen chains. The fluorescence study of Zn-MOF indicated that the maximum emission peak is 449 nm (λex=335 nm), and it had varying degrees of quenching effect on Cr₂O₇²⁻and CrO₄²⁻ in water, the limits of detection are 4.29×10⁻⁴ M and 9.19×10⁻⁵ M, respectively. It also showed good recycling ability, which was a potential multi-functional anion fluorescence probe material. In addition, the dye adsorption and separation experiments of Zn-MOF showed that it can adsorb MB⁺ and MG⁺, but almost no adsorption for MO⁻, and can effectively separate MB⁺ and MG⁺ from the mixed solution of MB⁺/MO⁻ and MG⁺/MO⁻. It was a potential multi-functional material for the capacity to selectively separate cationic dyes from anionic and cationic mixed solutions, as well as selective recognition of Cr₂O₇²⁻and CrO₄²⁻anions.