Advances in heterogeneous catalysts for sustainable PET upcycling: from mechanistic understanding to catalyst design

Polyethylene terephthalate (PET) is one of the most widely used plastics owing to its low cost, durability, and versatility in packaging, textiles, and engineering applications. However, the rapid accumulation of PET-based disposables and fibers has created a serious environmental burden, underscoring the urgent need for efficient and sustainable upcycling technologies. Conventional approaches-including solvent-based depolymerization and thermal decomposition-suffer from key drawbacks such as non-recyclable solvents, catalyst recovery difficulties, high energy requirements, and low selectivity for high-value products. Heterogeneous catalysts, including metals, metal oxides, and zeolites, have recently emerged as promising alternatives that enable recyclable operation, controllable surface properties, and precise regulation of reaction pathways. These systems enhance process efficiency, lower energy input, and improve selectivity toward high-value products such as bis(2-hydroxyethyl) terephthalate (BHET), dimethyl terephthalate (DMT), and aromatic hydrocarbons (BTX). Recent advances highlight how acid-base characteristics, metal dispersion, and metal-support interactions dictate product distribution, providing new opportunities for rational catalyst design. This review summarizes the state of the art in heterogeneous catalyst design for PET upcycling, emphasizing mechanistic insights, strategies for tailoring catalyst properties, and the integration of multifunctional catalytic systems. Future directions are also outlined, including the development of hydrogen-independent pathways, low-solvent or solvent-free systems, and durable catalysts capable of handling complex real-world PET wastes together, these efforts will be critical to advancing PET upcycling technologies from laboratory studies to scalable, industrially viable processes that support a circular plastics economy.