Synthesis and characterization of open and sandwich-type polyoxometalates reveals visible-light-driven water oxidation via POM-photosensitizer complexes

摘要

The trivacant triruthenium-substituted polyoxometalate α-K6Na[{Ru3O3(H2O)Cl2}(SiW9O_(34))]·17H2O (1) and two sandwich-type Co- and Ni-containing silicotungstates K_(11)Na1[M4(H2O)2(SiW9O_(34))2]·nH2O (M = Co~(2+), Ni~(2+)) (2, 3) based on the same Keggin-type building block were obtained through variation of a solution-based protocol. All compounds were investigated with respect to their performance as visible-light-driven water oxidation catalysts (WOCs). Analytical characterizations and photocatalytic reactivity of (1) are correlated with results of B97D/Def2-TZVP computation. The WOC activity of (1) and (2) was found to arise from their immobilization into a recyclable POM-photosensitizer complex (POM-PS). These POM-PS complexes are formed in the initial phase of the reaction, and they prevent POM decomposition into colloidal oxide catalysts.