A novel dual-functionalized ionic liquid biphasic absorbent with direct rich-phase regeneration and energy-saving properties was designed through experiments combined with quantum chemical calculations

To achieve superior regeneration properties of the CO 2 -rich phase without additional auxiliary measures in biphasic CO 2 absorbents (e.g., N 2 purging or co-activators), a dual-functionalized ionic liquid biphasic solvent of N-Aminoethylpiperazine-Lysine/N-Propanol/water ([AEPH][Lys]/NPA/H 2 O) was designed for CO 2 capture. It demonstrates a remarkable CO 2 loading of 1.847 mol·mol −1 , while the rich volume being only 53.0 % of the total absorbent and the viscosity as low as 6.10 mPa·s. Remarkably, 87.26 % regeneration efficiency was achieved under 393.15 K for 40 min without additives, and the regenerated lower phase could homogeneously recombine with the upper phase. After 10 cycles, regeneration efficiency remained at 84.67 %, while energy consumption was only 1.90 GJ·ton -1 CO 2 (49.87 % lower than MEA). 13 C NMR revealed that bicarbonate/carbonate dominated the CO 2 products, as well as some carbamates and a small amount of propyl carbonates. The reaction pathways of bicarbonates/carbonate based on quantum chemical calculations were indicated that through base-catalyzed hydration of tertiary amines on AEPH + cations, hydrolysis of carbamates and the reaction of water with CO 2 . The bicarbonate/carbonate exhibits lower thermal stability than carbamates, facilitating efficient regeneration. Based on MPI index, solvation-free energy and weak intermolecular interactions analysis, the solubility of CO 2 products in water is higher than NPA. This absorbent demonstrates significant potential for industrial CO 2 capture applications.