Catalytic Depolymerization and Upcycling of PET Waste into Potentially 3D-printable and Reprocessable Thermoset

The rapid rise in plastic waste, coupled with the limitations of existing recycling technologies, necessitates the development of efficient and sustainable catalytic systems for polymer depolymerization. In particular, the chemical recycling of polyethylene terephthalate (PET) requires robust system that enable high catalytic activity, facile recovery, reusability and improved process efficiency. In this study, a magnetically recoverable eucalyptus leaf ash-functionalized Fe 3 O 4 (ELA@Fe 3 O 4 ) nanocatalyst, derived from eucalyptus leaf ash, was synthesized via a green co-precipitation approach and applied for the efficient glycolysis of post-consumer polyethylene terephthalate (PET). Under optimized conditions (190 °C, 4 h, PET:EG = 1:8, 1 wt% catalyst), complete PET conversion with up to 93% yield of bis(2-hydroxyethyl) terephthalate (BHET) was achieved. The catalyst exhibited good recyclability over multiple cycles with moderate loss activity. Comprehensive spectroscopic and thermal analyses confirmed the high purity of the recovered BHET. Importantly, the depolymerized monomer was further upcycled into a dynamically crosslinked thermoset network via Diels-Alder chemistry, enabling thermal reprocessability. The thermo-reversible nature of this network facilitate the fabrication of complex three-dimensional geometries, demonstrating its potential as a feedstock for additive manufacturing. By establishing a complete valorization chain from waste plastic to reprocessable, shape-programmable materials, this integrated approach presents a sustainable and scalable pathway for converting plastic waste into value-added functional materials.