Controlling CO_2 emissions from low-concentration sources like coal-fired power plants and steel mills is crucial for achieving "carbon neutrality". Amine-based CO_2 capture technology is a leading contender for industrial application. This study aims to overcome limitations in energy consumption associated with amine-based processes by developing an efficient phase-separating CO_2 absorbent. The structural effeets of primary and secondary amines on the phase separation characteristics of amine-n-butanol-water absorbents after CO_2 absorption were investigated. The role of tertiary amines in the absorption-desorption and phase separation performance of 3AP-NBA-H_2O was also studied. Experimental results showed that the 3-aminopropanol (3AP)-n-butanol (NBA)-water absorbent had certain advantages in terms of rich CO_2 phase viscosity, amine distribution, volume, and phase transition critical point, indicating good phase separation characteristics. The addition of tertiary amines significantly reduced the viscosity of the rich CO_2 phase while increasing the CO_2 cycling capacity and desorption rate per unit volume of the solution. The novel 20%3AP-10%N,N-dimethylethanolamine (DMEA)-40%NBA-30%H_2O phase-separating absorbent had a rich phase volume of 61.2% and a viscosity of only 6.73 mPa · s. The proportion of amine in the rich phase was 91.2%, with desorption rate and CO_2 cycling capacity reaching 72.00% and 1.42 mol · L^-1, respectively. Compared to the absorbent with 30%3AP-30%NBA-40%H_2O, the desorption rate and CO_2 cycling capacity were improved by 88.6% and 86.8%, respectively, while showing an improvement of 46.8% and 13.6% compared to a 30% monoethanolamine (MEA) solution.