Advances in CO2 Absorption by Deep Eutectic Solvents

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.