Low‐temperature transesterification strategy for universal upcycling of waste polyesters into high‐value esters

Waste polyesters pose a severe environmental challenge and require transformative upcycling strategies to achieve a circular plastic economy. Distinct from conventional methanolysis relying on stoichiometric external alcohols or water‐triggered esterolysis, this study proposes a novel universal low‐temperature transesterification strategy for the upcycling of diverse polyesters into high‐value esters, using an internally driven self‐sustained transesterification cycle where, triggered by trace alcohols, dimethyl carbonate (DMC) dynamically exchanges its alkoxy groups with diols released from the polyester backbone. Typically, polyethylene terephthalate (PET) can be efficiently transesterified into dimethyl terephthalate (DMT) and ethylene carbonate (EC), reaching peak yields of 96% and 86%, respectively, under mild conditions. The self‐sustained transesterification strategy shows broad applicability to various types of polyesters, mixed textiles, post‐consumer plastics, and can also be extended to polyester upcycling using other alcohols and alkylating agents, which significantly reduces energy consumption and carbon emissions compared to traditional alcoholysis‐based systems, providing a scalable route for plastic circularity.