Deep Eutectic Solvents Consisting of a Dicationic Ionic Salt with Multiple Active Sites and Ethylene Glycol Derivatives for Reversible SO2 Absorption

Deep eutectic solvents (DESs) have been applied widely in the field of SO2 separation because of their unique properties. In this work, a series of DESs consisting of a dicationic ionic salt and ethylene glycol derivatives were synthesized to capture SO2 reversibly. Among these DESs, the diazabicyclooctane-1,2-bis(methoxy) chloride salt plus ethylene glycol TLDME-EG(1:4) exhibited the best SO2 uptake and SO2/CO2 selectivity up to 9.58 mol<middle dot>kg(-1) and 30.61 at 298.2 K and 1.0 bar, respectively. The mechanism study based on NMR and FTIR further confirmed that their excellent SO2 absorption capacity was the combined effect of the chemical, quasi-chemical, and physical interactions between SO2 and the multiple active sites. Moreover, the absorbed SO2 could be completely desorbed, and the absorbent could also be reused. As a result, DESs reported in the current work highlight good application potential in SO2 capture due to their excellent absorption and reversibility performance.