Hacking a Brønsted Photoacid to Capture and Directly Release a Lewis Acid: Applied to CO2 Photorelease

Abstract

Controlling reactivity using light remains an important goal in chemistry. Since acid-base reactions are central to nearly all chemical phenomena, photoacids are important molecules for controlling reactivity. Conventional photoacids release protons upon excitation or generate a Lewis acid through light-induced structural changes. Here, we report a conceptually different mechanism of Lewis photoacidity that leverages the excited-state mechanism of a Brønsted photoacid. It is well known that the Brønsted photoacid 2-naphthol releases a proton upon light absorption and converts to 2-naphtholate. We show that 2-naphtholate binds the Lewis-acidic CO₂ in the ground state and releases it upon photoexcitation. Through experimental and computational studies, we demonstrate that the spectroscopy and Förster cycle of this process are remarkably similar to those observed for proton release from 2-naphthol. This strategy provides a new approach for designing systems for reversible CO₂ capture and release and has potential for photochemistry of Lewis adducts beyond CO₂.