Effective synthesis of cyclic carbonates from CO2 and epoxides catalyzed by acetylcholine bromide-based deep eutectic solvents

Fixing CO 2 into cyclic carbonates is urgently required under green and eco-friendly conditions. Herein, we synthesized a series of bio-based deep eutectic solvents (DESs) for catalyzing cycloaddition reaction of CO 2 with epoxides. Notably, AcChBr-LMA (2:1) formed by acetylcholine bromide (AcChBr) and L -malic acid (LMA) shows the best catalytic activity (up to 98% yield) and excellent recyclability under mild conditions (0.1 MPa CO 2 pressure, 80 °C and 2 h). Mechanism studies have shown that there is a synergistic catalytic effect between the hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). • Acetylcholine bromide-based DESs are used as efficient catalysts for CO 2 conversion. • AcChBr-LMA (2:1) can be recycled without significant loss of activity. • Mechanistic studies reveal synergistic catalysis to promote cycloaddition of CO 2 and epoxides.