Graphical abstract Highlights • The homogenous solution was split into two immiscible liquid phases upon SO 2 loading. • The molar selectivity of SO 2 /CO 2 for the solution reached 440 at 1 atm and 293 K. • The absorption capacity reached 1.19 g/g and the viscosity was only 24.5 mPa s. • Phase-change mechanism is due to the polarity variation of absorbent after absorption. • N , N -dimethylcyclohexylamine was regenerated completely by microwave heating at 130 °C. Abstract In the present work, liquid-liquid phase-change absorption of SO 2 was investigated using N , N -dimethylcyclohexylamine (DMCHA) as an absorbent, and high boiling liquid paraffin (LP) as a solvent to reduce volatilization of the absorbent. The homogenous solution was split into two immiscible phases upon SO 2 loading. The phase-change mechanism was attributed to the polarity variation of DMCHA before and after absorption by forming the charge-transfer complex DMCHA·SO 2. The viscosity of the lower phase reached a maximum value of 24.5 mPa s at the absorption capacity of 1 mol SO 2 /mol DMCHA, and the viscosity of the corresponding upper phase was 46.4 mPa s. Both are lower than the reported viscosity of most ionic liquids. This solution exhibited extremely high mass selectivity of SO 2 /CO 2 with a value of 626. The mass absorption capacity was founded to be 1.19 g SO 2 /g DMCHA at 1 atm, which is comparable with the highest reported mass absorption capacity. At low partial pressure, the absorption capacity still reached 0.78 g/g at 0.1 atm, 0.43 g/g at 0.02 atm and 0.27 g/g at 0.001 atm. Furthermore, DMCHA could be completely regenerated in 10 min via microwave heating. All the results indicated this phase-change solution is a promising candidate for SO 2 capture. [ABSTRACT FROM AUTHOR]