Influence of acidic strength on the catalytic activity of Brّnsted acidic ionic liquids on synthesizing cyclic carbonate from carbon dioxide and epoxide

The chemical fixation of CO2 with epoxides to form cyclic carbonates was carried out with excellent selectivity and yield in the presence of Brّnsted acidic ionic liquids without using additional organic solvents and co-catalyst. The acidic strength of ionic liquids was determined and its effect on the synthesis of cyclic carbonates was investigated. The reaction conditions (temperature, CO2 pressure and reaction time) were optimized, and the Brّnsted acidic ionic liquids showed highly catalytic activity under the optimal reaction conditions. A plausible reaction mechanism was suggested and it was demonstrated that the carboxylic group in Brّnsted acidic ionic liquids had synergetic effect with halide. Moreover, the catalyst could be used five times without significant decrease in its catalytic activity.