Highly efficient absorption of carbon dioxide by EG-assisted DBU-based deep eutectic solvents

Superbase-based deep eutectic solvents (DESs) with different active sites for CO2 capture were synthesized in this work. The presence of ethylene glycol (EG) was found to play an important role for the CO2 absorption by DESs. The absorption capacities of [DBUH][MLU]-EG (1:1) and [DBUH](2)[DMU]-EG (1:2) were up to 0.138 w/w and 0.163 w/w under 40 degrees C and 1 atm, respectively, which were much higher than those of pure ionic liquids (IL). The enhanced CO2 absorption performance can be ascribed to the synergistic interaction of IL and EG. From the experimental results including nuclear magnetic spectroscopy analysis and quantum chemical calculations, it is found that EG can be activated by DBUH+. The activated EG had the ability to absorb CO2, thereby realizing the coordinated absorption by imino and hydroxyl groups in the absorption system. The main insight in this work is to identify DESs with EG assisted, high absorption capacity and good desorption potential. This insight provides a broader idea for the field of acid gas capture.