Development of biphasic solvent for CO2 capture by tailoring the polarity of amine solution

•Biphasic solvent was developed by tailoring the polarity of amine solution.•A dipole moment difference above 6.0 Debye was conducive to phase separation.•The rich phase had a CO2 capacity up to 6.06 mol/L with a volume ratio of 38.9%.•The mass transfer coefficient in biphasic solvent was 110.2% higher than 30 wt% MEA.•The estimated regeneration heat was 2.06 GJ/t CO2, 48.4% lower than 30 wt% MEA.