The coupling reaction of epoxides with carbon dioxide catalyzed by functional cross-linked polystyrenes and metal salts/functional polystyrenes systems

Abstract

A series of functional cross-linked polystyrenes was synthesized by the free radical copolymerization of divinylbenzene with functional styrenes and utilized as heterogeneous catalysts for the coupling of epoxides with CO₂. Investigations showed that the cross-linked copolymer functionalized by quaternary ammonium chloride (CP1) exhibited high catalytic activity in the coupling reaction and thermostability at elevated temperatures. Thus, CP1 was easily recycled from the reaction mixture by filtration and reused without obvious loss of activity. Moreover, the activity of CP1 can be greatly enhanced by adding conventional Lewis acids such as anhydrous FeCl₃ or AlCl₃. Thus, copolymer 1/FeCl₃ composites (1/1 molar ratio) transformed propylene oxide and CO₂ to propylene carbonate in 92% yield in 10 h at 110 °C with the composite catalyst loading of 0.25 mol% with respect to propylene oxide and can be reused after simple filtration without significant decline of activity.