Cooperative Effect of Oxygen Vacancies and Lewis Acid Sites in Selective Depolymerization of PET Plastic Over Ti‐Doped ZnO Catalysts

ABSTRACT Effective and selective recycling of polyethylene terephthalate (PET) into monomers and chemicals is essential. Herein, transition metal‐doped ZnO catalysts (M = Ti, Zr, and Hf) were synthesized and investigated for PET methanolysis. Among them, the Ti‐doped ZnO catalyst containing 7.5 wt% Ti (7.5Ti–ZnO) exhibited excellent activity, delivering 98.3% dimethyl terephthalate (DMT) yield at 170°C in 0.5 h, representing a 2.5‐fold higher activity than pristine ZnO. The catalyst also showed excellent activity in real and mixed PET wastes, confirming its broad applicability. Structural and spectroscopic analyses confirmed the incorporation of Ti into the ZnO lattice, resulting in a homogeneous solid solution with lattice distortion and an abundance of oxygen vacancies. NH 3 –TPD measurements revealed a substantial increase in acid sites with optimal Ti loading (7.5 wt%). The cooperative effect between oxygen vacancies and medium‐strength Lewis acid sites facilitated PET and methanol activation, and subsequent C–O dissociation via nucleophilic attack by methanol. Consequently, 7.5Ti–ZnO achieved a remarkable DMT formation rate of 510 mmol DMT g cat −1 h −1 . This study further underscores the potential of DMT as a versatile feedstock for the synthesis of virgin‐quality PET and other high‐value monomers, thereby enabling both closed‐loop recycling and open‐loop upcycling pathways toward a circular plastic economy.