Relationship between tertiary amine’s physical property and biphasic solvent’s CO2 absorption performance: Quantum calculation and experimental demonstration

•15 tertiary amines with various structure were selected for quantum calculation.•Cyclic tertiary amine were more sensitive to protonation process than branched tertiary amines.•The phase separation rate is mainly effected by electronegativity.•The position of phase separation peak is determined by polarity.•The absorption rate is controlled by both polarity and electronegativity. Biphasic solvent has been widely studied for CO2 capture due to its excellent energy-saving potentiality. However, its complex composition makes the prediction of main performances, like phase separation behavior or absorption rate, become obscure and difficult. This work investigated the relationship between the physical properties of tertiary amines and proton transfer process, phase separation behavior and absorption rate of biphasic solvents via quantum calculation and experimental results. The high electronegativity of tertiary amine N atom makes the biphasic solvent exhibit the fast phase separation rate and absorption rate, and maximum phase separation rate can reach 0.056 min−1. Furthermore, the increase of N atom polarity can delay the appearance of phase separation peak and stabilize the absorption rate during the counter-current absorption process. We believe that the relationship revealed by this work can deepen the understanding for screening and practical applying of biphasic solvents.