Copper-Mediated Oxidative Deconstruction of Polyethylene Terephthalate via Photoinduced Ligand-to-Metal Charge Transfer

Abstract

Polyethylene terephthalate (PET) is widely used in daily life due to its excellent properties. However, efficient recycling of PET is crucial to reduce environmental pollution and dependence on fossil resources. The existing chemical recycling methods primarily focus on activating the ester carbonyl group in molecules, often requiring excess nucleophilic reagents, high temperature and pressure, as well as costly metal catalysts. It is highly challenging to achieve efficient chemical recycling of PET under mild conditions. In this work, we developed a novel PET photocatalytic oxidative depolymerization method that efficiently converts PET into terephthalic acid (TPA) at room temperature using air as the oxidant. The key to the reaction lies in the activation of PET's C-H bonds via hydrogen atom transfer (HAT) by chlorine radicals, which are generated through a ligand-to-metal charge transfer (LMCT) process mediated by a copper catalyst. Various post-consumer plastic products can be efficiently degraded into TPA, demonstrating the practical applicability of this method. The mild reaction conditions, high product yield, and selectivity provide a viable strategy for PET oxidative degradation, highlighting its potential in polyester recycling.