Conversion of CO2 with epoxides to cyclic carbonates catalyzed by amino acid ionic liquids at room temperature

CO 2 utilization plays an important role in rational use of carbon resources and reduction of carbon emissions. It is still a challenge to achieve efficient CO 2 utilization by amino acid ionic liquids (AAILs) under room temperature and atmospheric pressure with cocatalyst- and solvent-free conditions. Herein, the newly developed AAILs including 1,1,3,3-tetramethylguanidine cation ([HTMG] + ) together with both amino acid and halogen as anions, were simply synthesized by neutralization reaction. Under mild conditions (30 °C, 20 h and 1 MPa CO 2 ), the cycloaddition reaction of CO 2 and propylene oxide could be efficiently catalyzed by [HTMG][His][I] with 99 % propylene carbonate yield and selectivity in the absence of additional solvent and cocatalyst. Notably, even at room temperature and atmospheric pressure for 72 h, [HTMG][His][I] also displayed 96 % yield and 99 % selectivity due to the cooperation of [HTMG] + , [His] 2– and [I] – . Meanwhile, [HTMG][His][I] performed excellent universality of various epoxides and reusability. Based on the characterization results of 1 H and 13 C NMR, it was verified that propylene oxide and CO 2 were simultaneously activated by the functional groups in [HTMG][His][I]. Hence, the reaction mechanism for CO 2 cycloaddition with epoxide catalyzed by [HTMG][His][I] was proposed. This work provided a simple strategy to prepare sustainable AAILs for efficient CO 2 utilization under very mild conditions of room temperature and atmospheric pressure (even the low CO 2 concentration at simulated flue gases).