Lewis Acid Dominant Windmill-Shaped V₈ Clusters: A Bifunctional Heterogeneous Catalyst for CO₂ Cycloaddition and Oxidation of Sulfides

Carbon dioxide (CO 2 ) and sulfides in gasoline are the main causes of air pollution. Considerable attention has been devoted to solving the problems, and the catalytic reaction seems to be a good choice. Owing to the high density of Lewis acid (LA) active sites and large numbers of open methoxide groups, polyoxovanadates (POVs) are an undisputed option as a heterogeneous catalyst for the CO 2 cycloaddition reaction and catalytic oxidation of sulfides. On the basis of the above, a series of V 8 clusters, [(C 2 N 2 H 8 ) 4 (CH 3 O) 8 V IV 8 O 12 ]·CH 3 OH ( V 8 -1a ), [(C 2 N 2 H 8 ) 4 (CH 3 O) 4 V IV 4 V V 4 O 16 ]·4CH 3 OH ( V 8 -1 ), [(C 3 N 2 H 10 ) 4 (CH 3 O) 4 V IV 4 V V 4 O 16 ]·5H 2 O ( V 8 -2 ), [(C 6 N 2 H 14 ) 4 (CH 3 O) 4 V IV 4 V V 4 O 16 ]·5CH 3 OH·2H 2 O ( V 8 -3 ), have been legitimately designed and triumphantly isolated. In the synthesis process, three different kinds of Lewis bases (LBs), ethanediamine, 1,2-diaminopropane, and 1,2-cyclohexanediamine, were used to modify LA { V 8 } clusters to form four diverting windmill-shaped configuration. Among them, the vanadium atoms in V 8 -1a are +4 valence of V IV, while the vanadium atoms in V 8 -1–3 are mixed valence states of V IV and V V . Magnetic property investigation indicates that the antiferromagnetic coupling interactions between V IV ions all exist in the four compounds. The compound V 8 -1 also demonstrated high catalytic activity in the cycloaddition of CO 2 to several epoxides under relatively mild conditions (70 °C, 0.5 MPa). More importantly, the reaction pressure 0.5 MPa is the lowest among the high nuclear polyoxometallates (POMs). Furthermore, V 8 -1 also has an excellent catalytic conversion for the oxidation of sulfides. The catalytic tests manifested that V 8 -1 was a very efficient difunctional heterogeneous catalyst for CO 2 cycloaddition reaction and catalytic oxidation of sulfides.