Protic ionic liquids: A highly efficient catalyst for synthesis of cyclic carbonate from carbon dioxide and epoxides

•Protic ionic liquids (PILs) for synthesizing cyclic carbonate without metal and solvent.•PILs’ catalytic activity was affected by its acidic strength.•PILs with excellent stability and recyclability.•The synergistic effects of cation and anion in PILs.

An efficient, inexpensive, easily prepared and sustainable catalytic system of protic ionic liquids was developed for cycloaddition of CO2 and epoxides to produce cyclic carbonates without using any co-catalyst and organic solvent. The effects of the acidity and structure of protic ionic liquid on the catalytic performance were investigated and the various reaction conditions were optimized. Notably, this catalyst was used for five times at least without appreciable loss of catalytic activity and applied for various epoxide for synthesis of corresponding cyclic carbonate in high selectivity and yield. Additionally, a mechanism for the synergistic effects of cation and anion in protic ionic liquids was also proposed.

Graphical abstractAn efficient, inexpensive, easily prepared and sustainable catalytic system of protic ionic liquid was developed for cycloaddition of CO2 and epoxides to produce cyclic carbonates without using any co-catalyst and organic solvent. This catalyst was used for five times at least without appreciable loss of catalytic activity and applied for various epoxide for synthesis of corresponding cyclic carbonate in high selectivity and yield. Additionally, a mechanism for the synergistic effects of cation and anion in protic ionic liquids was also proposed.Figure optionsDownload full-size imageDownload as PowerPoint slide