The Effect of DBU on Microstructure and CO2 Absorption of EmimCl-TEG and BmimCl-TEG Deep Eutectic Solvents

Graphical A strategy to improve CO 2 capture of AmimCl-TEG DESs is proposed, that is addition of equimolar DBU to DESs, then H-bonds between DBU and O−H of TEG cause TEG to deprotonate to anion and react with CO 2 , and the CO 2 absorption capacity by DESs-DBU is up to 2.94 mol kg −1 and is 11 times that of pure DESs, and the interaction of DESs with CO 2 changes from physisorption to chemisorption. Microstructure of deep eutectic solvents (DESs) based on EmimCl or BmimCl ionic liquid (IL) and triethylene glycol (TEG) was studied by FT-IR spectra. The influence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) on CO 2 absorption behavior and mechanism of DESs was investigated. FT-IR spectra of pure EmimCl-TEG and BmimCl-TEG DESs show that O−H⋅⋅⋅Cl − hydrogen bond interaction formed by IL and TEG gradually strengths with the increase in the molar ratio of IL to TEG, resulting in a corresponding increase in viscosity. Due to the lack of a chemical interaction site, the CO 2 absorption capacity of pure DESs at 313.2 K and 1.0 bar is only between 0.15 and 0.56 mol kg −1 . Surprisingly, the addition of equimolar DBU to DESs can significantly improve the CO 2 absorption capacity, which is up to 2.94 mol kg −1 at the maximum and similar to that of amine-functionalized DESs. CO 2 absorption mechanism characterized by FT-IR spectra indicates that DBU can form hydrogen bond with O−H of TEG, which leads to deprotonation of O−H of TEG into basic anion under the synergistic effect of O−H⋅⋅⋅Cl − hydrogen bond to achieve efficient CO 2 chemisorption via carbonate formation. The obtained results provide a strategy for effectively improving the CO 2 capture capacity of EmimCl-TEG and BmimCl-TEG DESs.