Programmable Photothermal Upcycling of Mixed Polyesters via Light-Intensity Gating on a Bifunctional Zn/Co-ZIF-C
Haoyi Wang1, Le Xu1, Chunying Si1
1State Key Laboratory of Water Pollution Control and Green Resource Recycling, National Engineering Research Center for Organic Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, 210023, China.
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Mixed polyester wastes with different chemical structures remain a key obstacle to achieving circularity in plastic utilization. Here, a programmable one-pot photothermal strategy is reported using a catalyst derived from a bimetallic MOF (Zn/Co-ZIF-C) through pyrolysis of a Zn/Co-integrated precursor. This system enables the efficient and sequential depolymerization of polycarbonate (PC), polylactic acid (PLA), and polyethylene terephthalate (PET) in mixed streams by simply tuning the irradiation intensity. Selective glycolysis of PC, PLA, and PET is triggered at ≈420, 520, and 650 mW cm-2, respectively, enabling stepwise monomer recovery in a single reactor. Density functional theory calculations reveal a dual-site cooperative mechanism, in which ZnO and Co-Nx sites cooperatively activate ester bonds and ethylene glycol, offering a mechanistic basis for the observed substrate-specific reactivity. The Zn/Co-ZIF-C catalyst exhibits broadband light absorption, strong catalytic activity, and excellent recyclability, maintaining over 95% PET conversion across five cycles. Moreover, it achieves monomer yields above 80% from nine real-world post-consumer plastics, while simultaneously removing dyes and performing magnetic separation. This work presents a robust and scalable catalytic platform for light-controlled, selective upcycling of complex polyester mixtures, offering new opportunities for sustainable plastic circularity.
