Highly efficient solid-state hydrolysis of waste polyethylene terephthalate by mechanochemical milling and vapour-assisted aging.

Despite significant methodological and technological advancements in chemical recycling of synthetic polymers, an efficient and quantitative conversion of post-consumer polyethylene terephthalate (PET) into terephthalic acid (TPA) under ambient conditions of temperature and pressure still remains a challenge. In this respect, the application of mechanochemistry and multiple advantages offered by solid-state ball milling and vapour-assisted aging have remained insufficiently explored. To further expand their potential, the implementation of organic solvent-free milling as a superior methodology for successful alkaline depolymerization of waste PET (e.g. bottles and textile) into TPA monomer in near-quantitative yields is reported herein. The solid-state alkaline PET hydrolysis is also shown to proceed in excellent yields under aging conditions in humid environment or in the presence of alcohol vapours. Moreover, the performance of mechanochemical ball milling and aging in the gram-scale depolymerization of PET into TPA is demonstrated.