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

Abstract

AbstractMicrostructure 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 CO2 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 CO2 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 CO2 absorption capacity, which is up to 2.94 mol kg−1 at the maximum and similar to that of amine‐functionalized DESs. CO2 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 CO2 chemisorption via carbonate formation. The obtained results provide a strategy for effectively improving the CO2 capture capacity of EmimCl‐TEG and BmimCl‐TEG DESs.