Efficient absorption of low-concentration CO2 by DBU/N-heterocyclic DESs aqueous solutions: A combination of shuttling role of nitrogen heterocycles and synergistic roles of DBU and water

A series of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)/N-heterocyclic DESs aqueous solutions were designed and synthesized as CO 2 capture agents. They showed excellent performance in absorption capacity, especially for the low-pressure CO 2 . The CO 2 loads in the absorbents were higher than 1.0 mol/mol when the pressure was just 0.1 bar. Through a combination of 13 C NMR spectra, FT-IR spectra and absorption experiments, a novel absorption mechanism was proposed. It was the shuttling role of the carbamate generated from CO 2 and nitrogen heterocycles, along with the synergistic roles of the DBU and water, that caused the high absorption capacity of the DBU/N-heterocyclic DESs for CO 2 . Meanwhile, the thermodynamic parameters, the activation energy and the regeneration efficiency were all measured to estimate the absorption performance of the DBU/N-heterocyclic DESs aqueous solutions for low-concentration CO 2 .