Integrated Photochromic‐Photothermal Processes for Catalytic Plastic Upcycling

Abstract Incorporating high‐energy ultraviolet (UV) photons into photothermal catalytic processes may enable photothermal‐photochemical synergistic catalysis, which represents a transformative technology for waste plastic recycling. The major challenge is avoiding side reactions and by‐products caused by these energetic photons. Here, we break through the limitation of the existing photothermal conversion mechanism and propose a photochromic‐photothermal catalytic system based on polyol‐ligated TiO 2 nanocrystals. Upon UV or sunlight irradiation, the chemically bonded polyols can rapidly capture holes generated by TiO 2 , enabling photogenerated electrons to reduce Ti 4+ to Ti 3+ and produce oxygen vacancies. The resulting abundant defect energy levels boost sunlight‐to‐heat conversion efficiency, and simultaneously the oxygen vacancies facilitate polyester glycolysis by activating the nucleophilic addition‐elimination process. As a result, compared to commercial TiO 2 (P25), we achieve 6‐fold and 12.2‐fold performance enhancements under thermal and photothermal conditions, respectively, while maintaining high selectivity to high‐valued monomers. This paradigm‐shift strategy directs energetic UV photons for activating catalysts and avoids their interaction with reactants, opening the possibility of substantially elevating the efficiency of more solar‐driven catalysis.