Acidic Protic Ionic Liquid‐based Deep Eutectic Solvents Capturing SO2 with Low Enthalpy Changes

With the aim of lowering energy consumption for gas regeneration, rational design of absorbents with low absorption enthalpy changes while retaining good gas solubility is of both scientific and practical significance. Herein, we demonstrated that acidic protic ionic liquid (APIL)-based deep eutectic solvents (DESs), which comprise N-ethylimidazole hydrochloride ([EimH]Cl) and ethylene glycol (EG), were able to reversibly absorb SO2 with high solubility (11.60 mol kg(-1)) and SO2/CO2 selectivity (655) at 293.2 K and 101.3 kPa. Meanwhile, [EimH]Cl/EG DESs exhibit very low enthalpy changes (?H-r(m)) ranging from -27.1 to -25.6 kJ mol(-1), and thus ease of desorption at very mild temperature conditions (303.2 K) with desorption ratios up to 99.6%. Recycling experiments showed that no obvious loss in capacity was found after six absorption-desorption cycles, suggesting good regeneration performance of [EimH]Cl/EG DESs. Moreover, spectroscopic analysis revealed the charge-transfer interaction between [EimH]Cl/EG and SO2.