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

J Phys Chem Lett. 2024 Aug 1;15(30):7782-7787. doi: 10.1021/acs.jpclett.4c01577. Epub 2024 Jul 24.

Abstract

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.