Photoacid for releasing carbon dioxide from sorbent

Carbon dioxide (CO2) is the most important greenhouse gas that causes global warming. Different sorbents, e.g. amines have been applied to capture CO2. Sorbent regeneration, which is currently conducted by thermal processes, is the most energy consuming step. In this work, we studied a photoacid, which can reversibly increase the acidity of a solution under light, and consequently lead to CO2 release. The photoactivity, acidity and solubility of the photoacid was tuned for CO2 release by structural design. The photoacid was mixed with morpholine, which is a well-studied amine for CO2 capture. Results showed that an aqueous solution containing the mixture can repeatedly capture and release CO2 under moderate irradiation of visible light. The CO2 released was nearly the same to that was captured, which indicates the high efficiency of this method.