N-hydroxysuccinimide based deep eutectic catalysts as a promising platform for conversion of CO2 into cyclic carbonates at ambient temperature

Abstract

Novel N-hydroxysuccinimide (NHS) based deep eutectic solvents (DESs) were facilely synthesized and structurally characterized by FT-IR, NMR and TGA techniques. The NHS-based DESs were demonstrated as a promising platform for efficient conversion of CO2 into cyclic carbonate. The optimized DES, i.e. iodide choline (ChI)/NHS with molar ratio of 1:2 exhibited excellent catalytic performance at 30 °C and 1.0 MPa CO2 pressure in the absence of cocatalyst, metal and solvent. The catalytic behaviour, catalyst recyclability and versatility were studied in details. The hydrogen-bond interaction between the ChI/NHS and substrate were also investigated. Based on the results, an insight into the synergetic catalytic mechanism involving hydrogen bond activation and ring-opening of epoxide was proposed. Compared with the reported DESs media, the NHS-based DESs present the higher-efficiency and greater advance in the synthesis of cyclic carbonate under ambient conditions.