Chemical Recycling of Polystyrene to Valuable Chemicals via Selective Acid-Catalyzed Aerobic Oxidation under Visible Light

Chemical recycling is one of the most promisingtechnologies that could contribute to circular economy targets byproviding solutions to plastic waste; however, it is still at an earlystage of development. In this work, we describe thefirst light-driven, acid-catalyzed protocol for chemical recycling of poly-styrene waste to valuable chemicals under 1 bar of O2. Requiringno photosensitizers and only mild reaction conditions, the protocolis operationally simple and has also been demonstrated in aflowsystem. Electron paramagnetic resonance (EPR) investigations anddensity functional theory (DFT) calculations indicate that singletoxygen is involved as the reactive oxygen species in thisdegradation process, which abstracts a hydrogen atom from a tertiary C-H bond, leading to hydroperoxidation and subsequentC-C bond cracking events via a radical process. Notably, our study indicates that an adduct of polystyrene and an acid catalystmight be formed in situ, which could act as a photosensitizer to initiate the formation of singlet oxygen. In addition, the oxidizedpolystyrene polymer may play a role in the production of singlet oxygen under light.