Combined experimental and computational study on the promising monoethanolamine + 2-(ethylamino)ethanol + sulfolane biphasic aqueous solution for CO2 absorption

•MEA + EAE + sulfolane biphasic absorbent was developed with better performance than MEA.•Tunable phase separation property was achieved by varying the concentration ratios.•Strong hydrogen bonding and interaction promoting phase separation were analyzed.•Liquid-liquid phase separation mechanism was revealed by classical MD simulations. To reduce the regeneration energy consumption for CO2 capture, an advanced monoethanolamine (MEA) + 2-(ethylamino)ethanol (EAE) + sulfolane biphasic aqueous solution was developed, and the phase separation mechanism was explored. The effects of the concentration ratio on the phase separation behavior, CO2 absorption performance, CO2 loading at the phase separation point, and CO2 desorption performance of MEA + EAE + sulfolane solutions were investigated comprehensively in experiments. The 3 M MEA + 2 M EAE + 5 M sulfolane showed the best properties with a large CO2 loading of 0.32 mol/mol at the phase separation point and the relative low regeneration energy consumption, which is comparable to 5 M MEA in absorption with an improved desorption performance. The molecular mechanism of phase separation was revealed by molecular dynamics simulations, illustrating that strong hydrogen bonding between amine products and water and enhanced intermolecular interaction among amine products, would promote an aggregation of amine products. This study provides a promising candidate for energy-efficient CO2 capture with molecular insights into a liquid–liquid phase separation.