Low-temperature polyethylene terephthalate upcycling by phenolic ionic liquids

Upcycling end-of-life polyethylene terephthalate (PET) to valuable chemicals is crucial for achieving circular economy. However, in practice it faces many challenges, such as harsh operation conditions and the generation of lower-quality products needing down-processing. Here we develop a phenolic ionic liquids-mediated process that is capable of complete PET conversion into valuable monomers at 70 °C in the presence of various nucleophiles. This is achieved primarily owing to the strong π‒π interactions between the phenolic anion and benzene rings on the PET main chains and the interactions between the phenolic anion and nucleophiles. The depolymerization of 100 g mixed real-life PET waste plastics was achieved with a high dimethyl terephthalate yield of 93.1%. In addition, the obtained PET ammonolysis monomers can be further copolymerized with carbon dioxide (CO 2 ) to synthesize polyurea, thereby eliminating the requirement for further separation and purification processes. Overall, this work not only offers insights into plastic upcycling process design but also presents a viable strategy for co-upcycling PET and CO 2 into valuable materials, paving the way to sustainable plastic waste management and circular economy.