Efficient Absorption of SO2 by Deep Eutectic Solvents Formed by Biobased Aprotic Organic Compound Succinonitrile and 1-Ethyl-3-methylimidazolium Chloride

We report that deep eutectic solvents can be formed by biobased aprotic organic compound succinonitrile (SN) functionalized as the hydrogen bond donor with solid ionic liquid 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) or 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF 6 ]). The results suggested the formation of intermolecular hydrogen bonds between the anions of imidazolium salts and the C–H hydrogen of SN. Moreover, the deep eutectic solvent [Emim][Cl]-SN(1:1) exhibited an attractive SO 2 absorption capacity (0.120 g SO 2 /g solvent) at low SO 2 partial pressure (2000 ppm), which was more than two times the amount captured by [Emim][Cl]-ethylene glycol (EG)(1:1) (0.047 g SO 2 /g solvent) at the same conditions, although the concentration of [Emim][Cl] in [Emim][Cl]-SN(1:1) (64.7 wt %) was lower than that in [Emim][Cl]-EG(1:1) (70.3 wt %). The high SO 2 absorption capacity of [Emim][Cl]-SN(1:1) was mainly because of the strong charge-transfer interaction between S of SO 2 and Cl –, which was investigated by using Fourier transform infrared spectroscopy and theoretical calculations.