Photoinduced Carbon Dioxide Release via a Metastable Photoacid in a Nonaqueous Environment

Capturing carbon dioxide (CO₂) from the atmosphere is a scientific and technological challenge. CO₂ can be captured by forming carbamate bonds with amines, most notably monoethanolamine (MEA). Regenerating MEA by releasing captured CO₂ requires that the carbamate solution be heated. Recently, photoacids were used to induce a pH change to release CO₂ from aqueous carbonate solutions. We report a merocyanine photoacid that releases CO₂ from nonaqueous carbamate solutions of MEA, which has a CO₂ loading capacity that is higher than that of water. On the basis of the absorption spectra of the photoacid in the presence of acids and CO₂, we show that the photoacid cycle and the CO₂ capture of MEA are two separate equilibria coupled to each other via protons. We demonstrate that irradiating the sample with 405 nm light induces the release of CO₂, which we detect using an in-line mass spectrometer. This work highlights an alternative path for optimizing a photoinduced CO₂ capture and release system.