Catalytic Depolymerization of Polyester Waste via Zinc Oxide-Decorated Silica

The aromatic units in the polyester materials are chemically robust, thermally stable, and widely used as engineering plastics. However, their chemical recycling remains a significant challenge. Herein, a zinc oxide-decorated silica (ZnO/SiO₂) catalyst is reported for the efficient chemical depolymerization of polyester into value-added bis(2-hydroxyethyl) terephthalate (BHET). The process affords BHET in 92.5% yield and 99% purity, with the yield remaining at 90% even after five cycles and an extended reaction time of 2 h. The strategy leverages surface defects on ZnO/SiO₂ to activate ethylene glycol and polarize ester carbonyls, thereby facilitating ester bond cleavage. A wide range of polyester waste plastics (i.e., mixed plastics, textiles, and packaging materials) are effectively depolymerized, underscoring the broad applicability of the catalytic system. Life cycle assessment demonstrates the viability of the recycling approach, achieving 235% energy savings and 104% reduction in greenhouse gas emissions compared to petroleum-based production of virgin BHET processes. Moreover, utilizing textile scrap further leads to a five-fold reduction in minimum selling price. This work offers a sustainable solution for managing PET waste and to realizing the circular economy.