Oxygen-bridged Zn single-atoms and ZnO sub-nanocluster for efficient depolymerization of waste polyethylene terephthalate

Metal migration strategy construct oxygen-bridged Zn-SAC/ZnO sub-nanocluster catalyst. • Catalyst attains full PET conversion, 90.7% BHET yield and high Zn space-time yield. • N-anchoring endows catalyst maintains 91.7% initial activity after multiple cycles. • The catalyst shows a wide applicability to diverse waste PET. • DRIFTS and DFT reveal atomic-level synergistic activation at Zn-SAC-cluster interface. Designing and constructing multi-site, highly active and stable heterogeneous glycolysis catalysts to convert polyethylene terephthalate (PET) into monomers is an important strategy for achieving sustainable plastic closed-loop recycling. Herein, we prepared an oxygen-bridged Zn single-atom and ZnO sub-nanocluster catalyst by “metal atoms surface migration strategy”. The optimized catalyst achieves nearly 100% PET conversion and bis (hydroxyethyl)terephthalate (BHET) yield of above 90.7% within 1.5 h, with its Zn active sites delivering a BHET space-time yield of 198.9 mmol BHET g Zn −1 h −1 . Owing to the robust anchoring by N-dopants, the catalyst retains 91.7% of its initial activity after multiple cycles. In-situ infrared and density functional theory (DFT) calculations revealed that the excellent catalytic performance of the catalyst is attributed to the synergistic effect of Zn single-atom and oxygen-bridged ZnO sub-nanocluster, which jointly promote the dual activation of the ethylene glycol hydroxyl group and the PET ester bond. This work emphasizes an atomic-scale engineering approach to maximize the density, accessibility, and stability of active sites, offering a viable idea for efficient plastic chemical recycling. Download: Download high-res image (153KB) Download: Download full-size image The Zn atoms coordinated within ZIF-8 were vaporized and migrated to the nitrogen-doped carbon carriers surface by the “metal atom surface migration strategy” to prepare a catalyst with oxygen-bridged Zn single-atom and ZnO sub-nanocluster structure, which promoted the dual activation of the ethylene glycol hydroxyl and PET ester group, achieving 100% PET depolymerization and 90.7% BHET yield.