Surface-accessible Zn Lewis acid sites on ZSM-5 for enhanced PET glycolysis

Polyethylene terephthalate (PET) glycolysis using heterogeneous catalysts is often limited by the poor accessibility of polymer chains to catalytic active sites, particularly in microporous systems. Herein, undercoordinated Zn Lewis acid sites were constructed on the external surface of ZSM-5 through controlled Zn modification, while strong interactions between Zn species and framework-associated Al enhance both Lewis acidity and catalyst stability. The resulting accessible Lewis acid sites facilitate polymer-catalyst contact, enabling complete PET conversion within 30 min under mild glycolysis conditions. The catalyst exhibited a high Zn utilization efficiency of 24.7 g PET ·g Zn -1 ·min -1 , maintained stable catalytic performance over 10 cycles with negligible Zn loss, and remained effective for post-consumer PET feedstocks. This work demonstrates that engineering the spatial distribution and coordination environment of Lewis acid sites is an effective strategy for heterogeneous polymer depolymerization.