Ag₃PO₄ enables the generation of long-lived radical cations for visible light-driven [2 + 2] and [4 + 2] pericyclic...

Photocatalytic redox reactions are important for synthesizing fine chemicals from olefins, but the limited lifetime of radical cation intermediates severely restricts semiconductor photocatalysis efficiency. Here, we report that Ag₃PO₄ can efficiently catalyze intramolecular and intermolecular [2 + 2] and Diels-Alder cycloadditions under visible-light irradiation. The approach is additive-free, catalyst-recyclable. Mechanistic studies indicate that visible-light irradiation on Ag₃PO₄ generates holes with high oxidation power, which oxidize aromatic alkene adsorbates into radical cations. In photoreduced Ag₃PO₄, the conduction band electron (e_CB^-) has low reduction power due to the delocalization among the Ag⁺-lattices, while the particle surfaces have a strong electrostatic interaction with the radical cations, which considerably stabilize the radical cations against recombination with e_CB^-. The radical cation on the particle's surfaces has a lifetime of more than 2 ms, 75 times longer than homogeneous systems. Our findings highlight the effectiveness of inorganic semiconductors for challenging radical cation-mediated synthesis driven by sunlight.