Polyoxometalate-based high-nuclear cobalt–vanadium–oxo cluster as efficient catalyst for visible light-driven CO2 reduction

A high-nuclear {Co16-V4} cluster was firstly isolated by pure inorganic lacunary POM units, which exhibits excellent photocatalytic activity for CO2-to-CO conversion under visible light irradiation. [Display omitted] A high-nuclear Co-V-O cluster was firstly isolated by lacunary polyoxoanion, resulting in the high-nuclear mixed metal-oxo cluster-containing polyoxometalate (POM), K4Na28[{Co4(O-H)3(VO4)}4(SiW9O34)4]·66H2O (1). In 1, the {Co4(O-H)3(VO4)}4{Co16-V4} core, composed of a {Co4O4} cubane, four {Co4(OH)3} qusi-cubanes and four VO4 units, was stabilized by four lacunary A-α-{SiW9O34} units. Photocatalytic study reveals that 1 exhibits excellent photocatalytic activity for CO2-to-CO conversion with high selectivity under visible light irradiation. The turnover number (TON) and turnover frequency (TOF) reaches as high as 10492 and 0.29 s−1, respectively. Compound 1 represents the first high nuclear TM cluster-containing POM (TM = transition-metal) with efficient visible light catalytic activity for CO2 reduction, and its photocatalytic activity is much higher than those of most reported molecular catalysts. Photoluminescence spectroscopy study reveals that photoexcitation of Ru-photosensitizer is followed by an efficient electron transfer to POMs to reduce CO2.