Effective catalytic system of zinc-substituted polyoxometalate for cycloaddition of CO2 to epoxides Original Research Article

A zinc-substituted sandwich-type polyoxometalate, Na12[WZn3(H2O)2(ZnW9O34)2]·46H2O, in conjunction with a Lewis base was found to be efficient for the cycloaddition of CO2 with epoxides to form cyclic carbonates. The catalyst system was tested for a few representative epoxides, including epichlorohydrin, propylene oxide and butylene oxide; the reactions were carried out at moderate CO2 pressure (0.4–1.0 MPa) in the temperature range 100–160 °C. Using the present catalyst system, one could obtain near-quantitative conversion and high selectivity with or without organic solvents. The zinc-substituted polyoxometalate part of the catalyst system is heterogeneous, easy to separate after completion of reactions and reusable for many runs.