Dynamic Self-Focusing Photothermal Localization Induced Mild Solvent-Free Upcycling of Polystyrene

The pervasive accumulation of nondegradable plastic waste, particularly microplastics, represents a critical environmental crisis demanding advanced recycling strategies. Here, we introduce a fully green, photo-driven process for polystyrene (PS) upcycling, enabled by a synergistic thermal-focusing and space-confined catalysis. Using earth-abundant MoO_3-x, it can efficiently absorb sunlight to generate localized heat, dynamically melting adjacent PS and spontaneously forming a core-shell MoO_3-x@PS structure. Critically, the intrinsically low thermal conductivity of PS creates a self-forming insulating layer, which traps thermal energy at the catalyst-polymer interface. This self-focusing thermal localization effect sustains a microscopic high-temperature reaction zone under ambient conditions, dramatically enhancing energy efficiency. The concentrated heat cleaves inert C─C bonds, while photogenerated charge carriers facilitate selective oxidative degradation. Consequently, we achieve 75.0% PS conversion with 70.5% combined yield of valuable products, predominantly benzoic acid crystals that spontaneously separate post-reaction. Operating without solvents or external heating, our strategy transforms waste PS into valuable chemicals using only sunlight. This work establishes a new paradigm for solid-state photothermal upcycling, leveraging interfacial thermal localization to enable a truly sustainable light-to-chemicals circular path.