An efficient method for the synthesis of cyclic carbonates from CO ₂ and epoxides using an effective two-component catalyst system: Polymer-supported quaternary onium salts and aqueous solutions of metal salts

A highly efficient method for the synthesis of cyclic carbonates from carbon dioxide and epoxides in the presence of polymer-supported quaternary onium salts (PS-Q⁺X^-) and aqueous solution of metal salts under mild conditions, is described. In comparison with conventional homogeneous catalysts, immobilized tributylmethylammonium chloride (PS-TBMAC) is a recyclable, effective catalyst for the studied reaction. The presence of an aqueous solution of zinc iodide as a co-catalyst enhances significantly the catalytic activity of PS-TBMAC. Using this two-component catalyst system (polymer-supported quaternary onium salts and aqueous solution of metal salts), the reaction of CO₂ with selected epoxides can be conducted with high product yield (71-91%) and selectivity (97-99%) under mild reaction conditions (temperature 110 °C and initial CO₂ pressure 0.9 MPa). Propylene carbonate was obtained in the best yield (91%). In addition, the advantages of this method include a short reaction time, solvent-free conditions, and an easy separation of catalyst system.