Upcycling of Polystyrene to Styrene via a Lewis Acid–Base Synergistic Catalyst ZAS-16(Vo) in Aromatic Solvents

Plastic pollution, particularly from recalcitrant polystyrene (PS), poses a severe challenge to environmental sustainability. Here, we report a solvent-assisted catalytic strategy for addressing this issue. First, leveraging the tunable surface chemistry of spinel structures, we designed and synthesized a defective ZAS-16(Vo) catalyst. Its abundant oxygen vacancies effectively modulate the surface acid–base properties, creating concentrated and well-matched Lewis acid–base sites. Subsequently, with the cooperation of a solvent, this system achieves remarkable depolymerization performance, with 98.82 wt % conversion and 76.21 wt % yield of styrene. In this process, the Lewis acid sites of the catalyst initiate C–C bond cleavage, while the base sites stabilize key intermediates and steer the reaction along the desired pathway. The solvent not only provides sufficient solubility to promote polymer disentanglement but also significantly enhances the chain mobility of PS, thereby creating a favorable environment for catalytic reactions. Finally, by combining in situ characterization with molecular dynamics simulations, we elucidate the reaction mechanism at the molecular level, offering new insights into closed-loop chemical recycling of plastics.