Three metal–organic compounds based on [SiMo12O40]4-: Synthesis, structures and properties

Three polyoxometalate-based metal–organic complexes with the ability to treat pollutants in water were obtained under hydrothermal conditions using two flexible bis(triazole) organic ligands, [Cu(bte)₂(H₂O)]₂[SiMo₁₂O₄₀]·2H₂O (1), [Cu(btb)₂]₂[SiMo₁₂O₄₀]·H₂O (2) and [Cu(btb)₂(H₂O)]₂[SiMo₁₂O₄₀] (3) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane; btb = 1,4-bis(1,2,4-triazol-1-yl)butane). In compound 1, Cu²⁺ ions are linked by bte into a two-dimensional network layer with [SiMo₁₂O₄₀]^4- anions filled between the layers as guest molecules. In compound 2, [SiMo₁₂O₄₀]^4- anions act as four-connected ligands to coordinate with Cu²⁺ and fill in the pores of the three-dimensional framework constructed by Cu²⁺ and btb. In compound 3, [SiMo₁₂O₄₀]^4- anions act as guest molecules to fill the channels of the two-dimensional layer formed by Cu²⁺ and btb. The electrochemical characteristics were studied, such as cyclic voltammetry, electrocatalytic reduction and oxidation of water contaminants, and current sensing of BrO^3-. The photocatalytic degradation of organic dye pollutant MB (methylene blue) performance was also investigated under visible light conditions.