118: Solvent-swing-based CO2 capture for direct air capture using aralkylamines

Abstract: The separation of acids and bases formed through acid–base interactions generally require an input of energy to shift the equilibrium toward dissociation. In amine-based CO2 capture systems, basic amines react with acidic CO2 to form amine- CO2 complexes, while the reverse process, namely CO2 release and concentration, typically relies on external energy sources such as heat, pressure, light, or electricity. As a result, the regeneration step remains one of the major energy-intensive components in CO2 capture processes employing amines. Here, we report that CO2 absorbed by aralkylamines can be released by altering the equilibrium conditions through solvent addition at room temperature, without supplying external energy. When a suitable solvent is introduced into the CO2-loaded amine system, the balance between bound and free CO2 is shifted toward dissociation because of changes in solubility and phase behavior. In this process, CO2 is separated from the amine phase while the basic amine is regenerated. This method does not rely on heating or pressurization but instead employs inexpensive and highly volatile solvents. Notably, the efficiency of CO2 release shows no clear relationship with the boiling point of the solvent, suggesting that the solvent-dependent stabilization of the amine and amine– CO2 states governs the equilibrium shift. These results demonstrate that CO2 release from amine-based absorbents can be achieved through state control rather than direct energy input, providing a new perspective for the design of low-energy CO2 capture and separation systems.