The good performance of our new fluorenyl photobases shows that incorporation a 4-electron ring into the carbocation can encourage excited-state hydroxide dissociation to create Baird aromaticity, yet also favour subsequent recombination of the ground-state antiaromatic cation with hydroxide. Structureactivity relationships illustrate that the effective basicity of the photobase must be precisely tuned for efficient CO2 separations. With the optimal system, capture was demonstrated from ambient air, followed by release into an enriched output stream. Ultrafast spectroscopic investigations show that hydroxide ion release occurs on a sub-ps timescale with high quantum efficiency. These studies suggest that photoreversible hydroxide emitters merit further investigation as tools for CO2 capture and in other diverse applications suitably regulated by light-driven equilibria.