Catalyst-Free, Autoinductive Photochemical Upcycling of Aromatic Polymers and Mixed Plastics via Autosensitization

Photochemical upcycling of polymers is a promising strategy for mitigating the plastic-waste crisis; however, many recent advances have centered on developing new and often costly photocatalysts. In contrast, the auto-sensitized photoreactivity of aromatic polymers such as polystyrene (PS)-albeit documented for decades-has remained essentially unexploited for practical upcycling. Here we leverage this overlooked reactivity to develop a catalyst-free, autoinductive platform that converts PS into benzoic acid under visible light irradiation in air. The approach extends to other aromatic polymers including polyethylene terephthalate (PET), polycarbonate, polyether sulfone (PES), and epoxy resins, as well as biomass feedstocks such as lignin. Importantly, convergent mechanistic experiments and DFT calculations support a solventenabled pathway in which autosensitization-derived superoxide reacts with chloroalkanes (via S N 2) to form peroxy intermediates, generating alkoxy and, via β-scission, chlorine radicals that abstract C-H bonds along polymer backbones, propagating oxidative chain cleavage. In turn, oxidized PS oligomers and in situ produced HCl drive autoinductive rate acceleration. This intrinsic PS photoreactivity further enables co-upcycling with non-aromatic polymers in mixed feeds and remains effective in a model halogenated solvent waste mixture, pointing to potential synergy between mixed plastics/biomass valorization and solvent waste management.