Accelerating Screening of Phase Separation Agents for Carbon Dioxide Capture: A Machine-Learning Framework with Interpretable Quantum Chemical Insights

Against the backdrop of addressing climate change and reducing carbon emissions, carbon dioxide capture technology has gained increasing significance as a key approach toward achieving global carbon neutrality. However, in the development of phase change absorbents, current screening methods for phase separation agents (PSAs) predominantly rely on static empirical parameters, neglecting electronic effects and phase equilibrium mechanisms, which somewhat restrict the improvement of screening efficiency and accuracy. This study innovatively proposes a novel paradigm integrating quantum chemistry and machine learning. A total of 434 experimental systems with amine, PSA, and water at a 1:2:2 ratio were constructed, from which 358 valid data sets were selected. A three-dimensional quantum chemical descriptor system encompassing 48 dynamic electronic parameters was established, accompanied by an innovative anion-centered molecular characterization method for the reaction states. A two-stage machine learning framework was employed: the random forest algorithm evaluated three types of descriptors and identified 34 key features, with particular emphasis on anion-related descriptors such as Orbital Discrete Index and Electrostatic Potential. After the six machine-learning models were compared, CatBoost was identified as the optimal classifier, achieving a test accuracy of 89.7% and a phase change recall of 96.3%. Interpretive analysis based on SHAP revealed that PSAs with lower mean Orbital Discrete Index values facilitate phase separation by weakening the hydrogen bond network, while the geometric feature (longest interatomic distance) and electronic property (minimum electrostatic potential) of organic amine anions synergistically drive the reconstruction of the phase interface. Validation in a 3-(dimethylamino)propylamine system demonstrated a prediction accuracy of 83.3%, significantly reducing experimental costs. This study provides an accurate and interpretable solution for the rational design of PSAs, strongly promoting the development of high-efficiency carbon dioxide capture materials.