Synthesis of cyclic carbonate from CO2 and epoxide using bifunctional imidazolium ionic liquid under mild conditions

The bifunctional imidazolium ionic liquids ([HEMim][Glu], [HEMim][Asp], [HEBim][Asp], [HEBim][Ala], [HEBim][His]) were successfully synthesized and characterized by H-1 NMR, C-13 NMR, COSY, HSQC and FT-IR spectroscopy. The ionic liquids performed as bifunctional catalysts and exhibited high catalytic activity for the cyclic carbonate synthesis from CO2 and epoxides under mild conditions with excellent yields in the absence of any solvents or co-catalysts. The reaction time, reaction temperature, CO2 pressure and the amount of ionic liquid were systematically investigated. The catalyst can be reused for at least four cycles without any significant drop in the catalyst activity and hence represents a reasonably environmentally benign chemical process for CO2 fixation.