Sulfur-containing amino acid-derived ionic liquid as a halogen-free catalyst for CO2 mild transformation into cyclic carbonates

In this study, a novel, easily prepared and stable acid-derived ionic liquid [DBUH](2)[Cys] containing -S- anion was synthesized and used to catalyze the reactions of CO2 and epoxides. It was found that halogen-free IL could promote this kind of reactions under mild conditions, and high yields of cyclic carbonates were obtained. Moreover, [DBUH](2)[Cys] could be reused at least five times without any obvious loss in catalytic activity. Compared with the common amino acid-derived ionic liquids, the -S- anion effectively promotes the catalytic activity of [DBUH](2)[Cys], resulting in its high catalytic performance.