Deep eutectic solvents (DESs), a new class of green solvents, have attracted considerable attention for CO2 capture. In this study, we synthesised DESs using a superbase, 1,5-diazabicyclo [4.3.0] non-5-ene (DBN), as the hydrogen bond acceptor and a weak acid, diethylene glycol (DEG), as the hydrogen bond donor in different molar ratios to achieve efficient and reversible CO2 absorption. Experimental results indicate that DES2 (DBN:DEG = 1:2) exhibits optimal CO2 absorption performance (a maximum absorption capacity of 0.275 gCO2/gDES. Deep eutectic solvents at 30°C and flow rate of 30 mL/min). Nuclear magnetic resonance (NMR) spectroscopy reveals that DEG activated by DBN in DESs can react with CO2 to form carbonates, thereby enabling CO2 capture. In addition, monoethanolamine was added to the DESs as a promoter, thereby enhancing the CO2 absorption performance, with a maximum absorption capacity of 0.316 gCO2/gDES. 13C NMR and Fourier transform infrared analyses revealed that the amino and hydroxyl groups in the DESs can simultaneously react with CO2 to form carbamate and carbonate, achieving synergistic absorption.