Transition Metal-Catalyzed Chemical Recycling and Upcycling of Polyethylene Terephthalate.
The rapid growth of the polymer industry has driven the widespread application of polyester plastics, especially polyethylene terephthalate (PET). However, the nonbiodegradability of waste PET poses persistent threats to ecosystems. Conventional mechanical recycling struggles to achieve closed-loop material circulation and preserve intrinsic material properties. Therefore, developing efficient, low-energy chemical recycling technologies that depolymerize waste PET into monomers or high-value chemicals has become a critical route toward a circular plastic economy. This review systematically presents various transition metal-catalyzed chemical depolymerization processes for waste PET, with a focused analysis of reaction mechanisms and performance of different catalytic systems in key reactions such as glycolysis, hydrolysis, hydrogenolysis, and methanolysis. Furthermore, the review outlines future research directions for enabling high-value, closed-loop recycling of waste polyesters, including rational catalyst design and process optimization and integration. Overall, this review aims to provide theoretical guidance and technological insights for the sustainable chemical recycling of polyesters.