Synergy of carbanion siting and hydrogen bonding in super-nucleophilic deep eutectic solvents for efficient CO₂ capture

Carbanion-based ionic liquids are proposed and utilized as the key components for the construction of five super-nucleophilic deep eutectic solvents (SNDESs) in the paper. The super-nucleophilic nature of carbanion-based ionic liquids (ILs) is found to enable the capture of CO2 with large absorption capacity. However, the absorption is very slow in the IL due to high viscosity. The synergy of carbanion siting and hydrogen bonding is found to enable high and fast absorption of CO2 in [N-2222][CH(CN)(2)]-ethylimidazole (Eim), and a synergistic absorption mechanism is proposed and validated from spectroscopic analyses and quantum calculations. The enthalpy change of CO2 absorption in [N-2222][CH(CN)(2)]-Eim is calculated to be -39.6 kJ mol(-1) according to the thermodynamic model, and the moderate value implies that both absorption and desorption of CO2 in the DES are favored and well balanced. The carbanion and hydrogen bond mediated by SNDESs provides a novel insight into the efficient CO2 capture.