One‐Reactor Upcycling of Waste Polyesters into Functional MOFs for Passive Radiative Cooling

Polyethylene terephthalate (PET), despite its extensive use, presents serious environmental concerns due to inefficient recycling and inevitable downcycling. In this work, a sustainable one-reactor upcycling strategy is developed to directly convert waste PET into functional metal-organic frameworks (MOFs). Using a biocompatible betaine catalyst and adopting a single-reactionvessel strategy, this integrated process substantially improves reaction efficiency and scalability. The strategy is further extended to other polyester plastics, such as polylactic acid (PLA), enabling the synthesis of six MOFs (Zn-BDC, Ca-BDC, Ni-BDC, Co-BDC, Zn-LA, and Ca-LA) with excellent crystallinity and tunable morphologies. When incorporated into polyvinylidene fluoride (PVDF) composite films, the PET-derived Zn-BDC exhibits superior passive radiative-cooling performance compared with conventional MOF-5 composites, achieving high solar reflectance (≈94.4%) and mid-infrared emissivity (≈95.5%), which lead to an average temperature reduction of 9.3°C below ambient conditions. Overall, this streamlined and scalable upcycling route provides an economically viable bridge between sustainable plastic-waste valorization and next-generation energy-saving materials.