A Review on CO ₂ Capture Using Phase Change Amine Absorbents

Mitigating climate change requires efficient CO2 capture technologies, yet conventional aqueous amines such as MEA suffer from high regeneration energy and chemical degradation. Phase-change amine absorbents (PCAAs) offer a promising alternative by undergoing liquid–liquid or liquid–solid phase separation upon CO2 absorption, concentrating CO2 in a small rich phase and lowering regeneration energy by ∼30–40%. This review outlines the development of PCAAs, their absorption mechanisms, phase-separation behaviors, and performance optimization strategies. Spectroscopic techniques (13C NMR, IR, Raman) and molecular simulations (DFT, MD) have advanced mechanistic understanding, while thermodynamic modeling and process simulations guide solvent design and scale-up. Finally, by clarifying key challenges─such as incomplete elucidation of reaction pathways, mass-transfer limitations, and inconsistent evaluation criteria─this work proposes a comparative framework that links molecular mechanisms to process-level performance, offering more targeted insights to support PCAAs in surpassing conventional biphasic amine systems and advancing toward large-scale CO2 capture applications.