CO2 capture with green ionic liquid and deep eutectic solvent: A comparative study

Abstract

Increasing the greenhouse gases in the atmosphere, mainly from human activities leads to the global warming phenomenon and poses a serious threat to life on the earth.Hence, there is a pressing need to mitigate greenhouse gases emission and overcome global warming. It is proven that Ionic liquids (ILs) and deep eutectic solvents (DESs) are fruitful materials to capture gases and reduce their emission. Here, we investigate the environmentally friendly and cost-effective cholinium geranate ([Cho][Ger]) IL and cholinium geranate:geranic acid ([Cho][Ger]:Ger acid) DES, for carbon dioxide (CO2) capture. To this end, the density functional theory (DFT) and molecular dynamics (MD) simulation approaches are employed to provide quantitative microscopic insight into the interactions between CO2 and IL/DES. The adsorption energies of IL…CO2 and DES…CO2 are explored through the DFT calculations and show stronger interaction between the IL…CO2 than DES…CO2. The MD simulation analyses including density profile, non-bonded energy, radial distribution function (RDF), and spatial distribution function (SDF) affirm the stronger interaction between the IL…CO2 than DES…CO2. Meanwhile, the DFT and MD simulation results reveal the strongest interaction between CO2 and [Ger] - anion of both IL and DES. Furthermore, the minimum potential of mean force (PMF) of CO2 at the IL-air interface represents the favorable adsorption of CO2 on IL. Overall, our molecular level findings which are not accessible through the experimental approaches could help experimentalists find high-efficient solvents for CO2 capture.