Advancements in amine-based biphasic absorbents for efficient and low-energy CO2 capture: a review

Amine-based biphasic absorbents offer a highly energy-efficient approach to post-combustion CO 2 capture by selectively enriching CO 2 and drastically reducing the solvent volume requiring thermal regeneration. While previous studies have emphasized general process evaluation and component screening, a systematic understanding of how aqueous versus non-aqueous environments regulate absorption kinetics, desorption efficiency, and phase-transition dynamics remains insufficient. This review provides a comprehensive evaluation of amine-based biphasic absorbents in CO 2 capture, focusing on fundamental structure-property relationships and molecular-level phase separation mechanisms. Special attention is given to molecular polarity variations, dipole moment modifications, and the molecular polarity index in governing reaction pathways, product distribution, and subsequent liquid-liquid or liquid-solid phase transitions. Amine biphasic systems are classified into aqueous and non-aqueous formulations, with a critical assessment of their inherent performance trade-offs, specifically the faster mass transfer in aqueous systems versus the ultra-low latent heat and regeneration energy in non-aqueous solvents. By elucidating these molecular drivers and macro-scale performance correlations, this review establishes a unified framework for the rational design of next-generation, low-energy biphasic absorbents for industrial CO 2 capture.