Multiscale Exploration of Dynamic Phase-Splitting Behavior for Biphasic Solvent in CO₂ Capture

Chemical absorption with biphasic solvents is considered a promising and energy-efficient route for CO₂ capture. However, achieving efficient dynamic phase splitting remains a significant challenge, primarily due to the unclear intrinsic relationship between amine species and their separation behavior. To address this issue, specific amino groups were controlled to develop biphasic solvents by incorporating various amines, the phase-splitting behavior of which was thoroughly investigated at the macro, micro, and molecular scales. It is found that the chemical structure of the amine is the dominant factor in regulating the phase separation behavior of the two-phase solvent, and the influence of the molar concentration is only a minor fine-tuning effect. The formation of immiscible clusters was reconstructed through molecular simulation, revealing the dominant role of hydrogen bonding between solvent species. Influenced by gravity, buoyancy, viscous forces, and surface tension, the immiscible clusters underwent sedimentation, coalescence, and breakup before dissolving into bulk phases with similar properties, ultimately forming two phases with well-defined boundaries. The phase-splitting kinetics were established based on the visualized records of cluster motion and the time-space profile of the CO₂/H₂O content. Overall, this work clarifies the complex influence of molecular polarity and cluster motion on various stages of phase-splitting behavior, elucidating a valuable perspective for the design and application of biphasic solvents.