From Traditional Depolymerization to Value-Added Upgrading: Upcycling of PET Fibers with Sustainable Chemistry and Renewable Energy

Polyethylene terephthalate (PET) is not only a major packaging plastic but also the dominant polyester used in fibers and textiles, including apparel, carpets, nonwovens, filtration media, and industrial fabrics. The growing accumulation of post-consumer PET bottles and textiles poses severe challenges to conventional recycling and accelerates the release of fibrous microplastics. Upcycling PET fibers into value-added chemicals, fuels, and functional materials therefore offers an important route toward sustainable fiber circularity. This work focuses on the mechanistic underpinnings of sustainable chemical strategies and the successful integration of renewable energy sources for converting PET into high-value chemicals. We first outline the fundamental cleavage chemistry of the PET ester bond. Subsequently, exciting progress in thermocatalysis, electrocatalysis, and photocatalysis is critically examined in detail, combining the PET waste transformation with sustainable chemistry and renewable energy. Next, the existing challenges and future perspectives are featured, aiming to advance molecular-level understanding and guide the design of closed-loop circular chemical processes. We envision a sustainable future where discarded plastics and fibers evolve from being an ecological concern to becoming a valuable chemical resource within the circular economy.