How is CO₂ absorbed into a deep eutectic solvent?

Deep eutectic solvents show great potential as CO₂ absorbents, which is highly desirable for the sustainable development of CO₂ reduction and prevention of global climate changes. Ab initio molecular dynamics simulations in the isothermal-isobaric ensemble at pressures of 1 MPa and 5 MPa and at the corresponding experimental density are carried out to investigate the CO₂ absorption in choline chloride: ethylene glycol deep eutectic solvent. Based on the structural analysis, there is a strong anion and hydrogen bond donor effect and a minor cation effect on CO₂ solvation in the solvent. Instead of cooperation, a competition between the anion and the hydrogen bond donor (ethylene glycol) for the interaction with CO₂ is indicated. While at a lower pressure, the ethylene glycol-CO₂ interaction dominates, at a higher pressure, it is the chloride-CO₂ interaction. Thus, it is possible to use the same advantages within the deep eutectic solvent as the CO₂ absorbent as in ionic liquids, but in the hydrogen bond, a donor can be exploited.