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 molkg(-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.