Photoacid for releasing carbon dioxide from sorbent.

Carbon dioxide (CO 2 ) is the most important greenhouse gas that causes global warming. Different sorbents, e.g. amines have been applied to capture CO 2 . 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 CO 2 release. The photoactivity, acidity and solubility of the photoacid was tuned for CO 2 release by structural design. The photoacid was mixed with morpholine, which is a well-studied amine for CO 2 capture. Results showed that an aqueous solution containing the mixture can repeatedly capture and release CO 2 under moderate irradiation of visible light. The CO 2 released was nearly the same to that was captured, which indicates the high efficiency of this method.