A Comprehensive Review of PET Chemical Depolymerization: Mechanisms, Catalyst Design, and Process Intensification...

The massive accumulation of polyethylene terephthalate (PET) waste necessitates efficient recycling technologies to mitigate environmental pollution. Chemical depolymerization converts PET into high-purity monomers, offering a promising route for closed-loop plastic circularity. This review systematically summarizes recent advances in catalytic PET depolymerization, emphasizing reaction mechanisms, catalyst design, and process intensification. We analyze major depolymerization routes, namely hydrolysis, methanolysis, glycolysis, and aminolysis while highlighting fundamental mechanistic insights such as nucleophilic transesterification and emerging β-cleavage pathways. Furthermore, we evaluate catalyst design principles for active sites (e.g., Brønsted and Lewis acids, bridged bimetallic centers, and defect-engineered structures) across various homogeneous and heterogeneous systems, including ionic liquids, metal-organic frameworks, and zeolites. Finally, we highlight recent progress in process intensification strategies, such as interfacial catalysis, microwave-assisted reactions, and tandem one-pot processes. By integrating mechanistic understanding with catalyst engineering, this review provides a comprehensive perspective and outlines future directions for sustainable, industrially viable closed-loop PET recycling.