Photochemical Aerobic Upcycling of Polystyrene Plastics via Indium Salt‐Mediated Synergistic Catalysis

The photochemical upcycling of polystyrene (PS) represents a sustainable method for the transformation of plastic waste into added‐value chemical feedstock. Herein, we propose a convenient and efficient photochemical catalytic system that integrates InBr 3 catalysis with bromine radical sources, such as tosyl bromide and N ‐bromosuccinimide (NBS). This approach enables the effective depolymerization of PS under mild conditions, providing benzoic acid in high yields. The protocol exhibited broad substrate tolerance, efficiently converting a variety of commercial and everyday PS‐based materials and was also successfully applied to a 1‐gram reaction. Comprehensive mechanistic investigations were performed, while applications to generate a series of value‐added compounds of potential pharmaceutical and industrial interest are highlighted. This study offers a practical method for the photochemical upcycling of PS waste through bromine radical‐mediated depolymerization.