Basicity-controlled DBN-based deep eutectic solvents for efficient carbon dioxide capture

Greenhouse gas emission reduction is an important factor to alleviate global warming. Therefore, the development of efficient and reversible carbon dioxide (CO 2 ) absorbent to control and reduce CO 2 gas emissions has become a hot topic of concern to the majority of researchers. In this study, 1,5-diazabicyclo [4.3.0]-non-5-ene (DBN) was used as cation, and 1,2,4-triaz (Triz), 2-methylimidazole (2-MeIm), 2-Oxazolidone (Oxa) with different pK a were used as anions to synthesize ionic liquids (ILs). Using the above ILs as hydrogen bond acceptor (HBA) and ethylene glycol (EG) as hydrogen bond donor (HBD), DESs were prepared to achieve efficient and reversible absorption of CO 2 . The results showed that the larger the pK a of anion, the better the CO 2 absorption performance, and the DESs reach the absorption equilibrium faster than ILs. [DBNH][Oxa]-EG (1:0.5) had the best absorption performance with the maximum absorption capacity of 0.171 g CO 2 /g DES. The results of 13 C NMR spectra analysis proved that IL and EG could react with CO 2 simultaneously to produce carbamate and carbonate, thus realizing the synergistic absorption of imino and hydroxyl group. From a microscopic perspective, DFT calculations confirmed this mechanism and explained the effect of pK a on CO 2 capacity. In addition, DBN-based DESs synthesized in this study exhibited excellent recyclability. • Three kinds of basicity-controlled DBN-based ILs/DESs are synthesized for CO 2 capture. • The relationship between pK a and CO 2 absorption capacity is investigated. • Both IL and EG can react with CO 2 to produce carbamate and carbonate, thus realizing the synergistic absorption.