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.