Efficient fixation of CO₂ into cyclic carbonates catalyzed by hydroxyl-functionalized poly(ionic liquids)

A series of hydroxyl-functionalized poly(ionic liquids) (PILs) were synthesized and employed as catalysts for the synthesis of cyclic carbonates from CO₂ and epoxides without the use of any co-catalyst or organic solvent. It was demonstrated that hydroxyl and bromide anion had an excellent synergetic effect on promoting the reaction, and the PILs catalysed co-polymerization of 1-vinyl-3-carboxyethylimidazolium bromide with the cross-linker divinylbenzene (DVB) was observed to be the most efficient, with nearly a 99% yield of propylene carbonate and 100% selectivity. The effects of temperature, pressure and reaction time on the reaction were also investigated. Moreover, the catalysts can be easily recovered and reused more than five times with only a slight decline in catalytic activity. This process carries huge industrial applications due to the reactions high efficiency and the ease of catalyst separation and recycling, which could be profitably applied to the development of fixed-bed continuous flow reactors.