Coupled CO ₂ absorption and phase separation with precise phase regulation on biphasic absorbent

Abstract

Liquid–liquid phase separation is an interesting phenomenon that generates two immiscible liquid phases during CO ₂ absorption or temperature swing. It provides a promising opportunity to optimize CO ₂ capture processes and reduce the energy penalty for solvent regeneration. However, precise control of phase behavior remains challenging. This work achieves controllable phase separation in amine‐ether‐water systems. Results show that adjusting the ether‐to‐water mass ratio enables the correlation between critical CO ₂ loading and temperature to reversibly shift from negative to positive. This rule is verified in various amines and ethers. Synergistic effects of temperature and CO ₂ absorption on phase separation are revealed by ¹³ C NMR and molecular dynamics simulations. This study deepens the understanding of phase separation and offers a theoretical basis for developing high‐performance CO ₂ absorbents for industrial applications.