Biphasic solvents are regarded as promising candidates for CO₂ capture but still suffer from the deficiency of inferior regenerability, which negatively affects their energy-saving potential. 2-Amino-2-methyl-1-propanol (AMP)-based absorbents have superior regenerability but poor phase-change performance. In this study, an effective strategy that using tetraethylenepentamine (TEPA) to regulate the phase change behavior of an AMP-pentamethyldiethylenetriamine (PMDETA) aqueous solution was proposed, aiming to develop a novel AMP-PMDETA-TEPA (A-P-T) biphasic solvent with good regenerability and excellent phase separation performance. The A-P-T biphasic solvent could realize a high CO₂ loading of 0.73 mol mol⁻¹ and a high desorption efficiency of 75.3%. Its sensible heat requirement significantly decreased to 0.14 GJ·ton⁻¹ CO₂, 78.1% less than the monoethanolamine solution. The ¹³C NMR characterization and quantum chemistry calculations indicated that with the introduction of TEPA, high polar TEPA-associated products were generated, which broke the original assimilation state of the A-P-T system and drove it to undergo phase change. Since the TEPA-associated products had a strong affinity to other CO₂-captured products and H₂O, they gathered together to form the CO₂-rich phase. In contrast, less polar PMDETA showed a relatively weak affinity to the TEPA-associated products and was solely separated from the solution to form the CO₂-lean phase.