Adjustable Upcycling of Polyethylene Terephthalate to Biodegradable Polymer Monomers by Mn-Catalyzed Solvent Switching Strategy.

Waste plastics represent a new resource for the chemical industry. In this study, we demonstrate a solvent-switching strategy to upcycle waste polyethylene terephthalate (PET) into monomer terephthalic acid (TPA) and key bulk feedstocks for biodegradable polymers, such as lactic acid (LA) or glycolic acid (GA). PET undergoes rapid and mild depolymerization into its monomers TPA and ethylene glycol (EG) under the catalysis of a manganese complex. When methanol (MeOH) is used as the solvent, it undergoes selective dehydrogenative coupling with in situ generated EG, efficiently yielding TPA and LA with yields exceeding 98%. By replacing MeOH with tert-amyl alcohol (t-AmOH), PET is quantitatively converted into TPA and GA. The PET conversion mechanism was elucidated through deuterium-labeling experiments and molecular model studies. This work presents a sustainable and innovative approach for upcycling waste PET into high-value products while opening a new route to synthesize biopolymer monomers, which are essential for developing chemically recyclable and biodegradable polymers, thereby advancing the production of sustainable single-use polymer products.