de Vrie et al. (2023): Solvation-Tuned Photoacid as a Stable Light-Driven pH Switch for CO2 Capture and Release

Anna de Vrie, Kateryna Goloviznina, Manuel Reiter, Mathieu Salanne, Maria R. Lukatskaya IN: Chemistry of Materials, https://doi.org/10.1021/acs.chemmater.3c02435

Photoacids are organic molecules that release protons under illumination, providing spatiotemporal control of the pH. Such light-driven pH switches offer the ability to cyclically alter the pH of the medium and are highly attractive for a wide variety of applications, including CO₂ capture. Although photoacids such as protonated merocyanine can enable fully reversible pH cycling in water, they have a limited chemical stability against hydrolysis (<24 h). Moreover, these photoacids have low solubility, which limits the pH-switching ability in a buffered solution such as dissolved CO₂. In this work, the authors introduce a simple pathway to dramatically increase stability and solubility of photoacids by tuning their solvation environment in binary solvent mixtures. They show that a preferential solvation of merocyanine by aprotic solvent molecules results in a 60% increase in pH modulation magnitude when compared to the behavior in pure water and can withstand stable cycling for >350 h.

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