To address the challenges of low capture efficiency and high energy consumption in capturing low-concentration CO2 from the flue gas of combined-cycle gas turbine (CCGT) systems

this study develops a novel biphasic absorbent based on a 3-dimethylaminopropylamine (DMPDA)/N

N-dimethylcyclohexylamine (DMCA)/H2O system. The CO2 capture performance

phase separation behavior

and reaction mechanism of the absorbent are systematically investigated through bubbling reactor experiments

combined with 13C nuclear magnetic resonance (NMR) characterization and quantum chemical calculations. The results show that when the absorbent composition is 30 wt.% DMPDA with a DMCA-to-H2O mass ratio of 6:4 (designated as DDH364)

the CO2 absorption capacity reaches 2.28 mol/kg at 313 K

and the cyclic capacity remains as high as 1.96 mol/kg after desorption at 383 K. The solution undergoes spontaneous phase separation after absorption

with the CO2-rich phase accounting for 48% of the total volume and exhibiting a low viscosity of only 44.6 mPa•s.The predominant product in the rich phase is DMPDACOO-

and the proton transfer preferentially occurs intramolecularly during protonation. The regeneration energy requirement is as low as 2.74 GJ/tCO2

representing a 38% reduction compared to the conventional 30% monoethanolamine (MEA) absorbent. These findings demonstrate that the DMPDA/DMCA/H2O biphasic absorbent offers fast absorption kinetics

low viscosity

and reduced regeneration energy consumption

thereby offering a promising solution for efficient low-concentration CO2 capture in CCGT systems.