Three ring-shaped Zr(iv)-substituted silicotungstates: syntheses, structures and their properties.

Three Zr(iv)-substituted polyoxometalate nanoclusters, H(Hdap)[{Zr(OH)(α-SiWO)}{Zr(OH)(β-SiWO)}]·8HO (1, dap = 1,3-diaminopropane), HNa[(Zr(OH))(ZrBO(OH))(β-SiWO)]·50HO (2) and HNa[(ZrBO(OH))(ZrBO(OH))(β-SiWO)]·40HO (3), were made by a hydrothermal reaction of trivacant [A-α-SiWO], Zr ions, and HBO under different alkaline conditions. Single-crystal X-ray structure analysis revealed that they are ring-shaped polyoxotungstate aggregates built by Zr(OH) ({Zr}) clusters and two types of dilacunary α-/β-SiWO ({α-/β-SiW}) fragments for 1, {Zr}, {β-SiW}, and ZrBO(OH) ({ZrB}) clusters for 2, and {β-SiW}, {ZrB}, and ZrBO(OH) ({ZrB}) clusters for 3, respectively, showing that the Zr-B-O clusters, {ZrB} and {ZrB}, have been introduced to the lacunary sites of polyoxometalates for the first time. The electrochemistry and electrocatalytic properties of 2 were studied, and it exhibited effective catalytic activities for the reduction of HO, NO, and BrO. Moreover, the catalysis of 2 for the oxidation reactions of various thioethers was investigated, and it was found that 2 possessed high conversion and remarkable selectivity.