Advances in CO2 Absorption by Deep Eutectic Solvents

Abstract

With global warming, more and more environmental problems have begun to appear, and people have gradually come to realize that the reckless emission of greenhouse gases will lead to a drastic deterioration to the ecological environment. In order to solve the environmental problems caused by global warming, more and more scientists have begun to work on improving the current situation of greenhouse gases emissions. CO₂ is a greenhouse gas that can be found everywhere in our daily life, and its contribution to the total greenhouse gas accounts for about 50%. Furthermore, the concentration of CO₂ is increasing with the advancement of human society. The main reason for the growth of CO₂ concentrations in the atmosphere is the extensive use of fossil fuels. Therefore, it is necessary to absorb CO₂ from industrial emissions. Many CO₂ capture methods have been proposed. As the research progressed, scientists found that deep eutectic solvents (DESs) show a bright future for CO₂ capture due to their advantages like high CO₂ absorption capacity, good solvent renewability, low price, less pollution, etc. Many articles have reported the absorption of CO₂ using DESs and in situ conversion of absorbed CO₂. This article reviews the progress of DESs in absorbing CO₂. DESs as absorbents for CO₂ absorption are discussed following the aspects of quaternary-ammonium-salt-based DESs, azole-based DESs, amine- and amino-acid-based DESs, ionic-liquid-based DESs, ternary DESs, and other types of DESs for absorbing CO₂. DESs cooperate with other methods to absorb CO₂. Lastly, in situ conversions of CO₂ in DESs are also discussed for regenerating DESs for energy saving. This article discusses general trends in the development of DESs for CO₂ capture and evaluates the challenging aspects of DESs for CO₂ absorption.