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

Chemical recycling is one of the most promising technologies that could contribute to circular economy targets by providing solutions to plastic waste; however, it is still at an early stage of development. In this work, we describe the first light-driven, acid-catalyzed protocol for chemical recycling of polystyrene waste to valuable chemicals under 1 bar of O2. Requiring no photosensitizers and only mild reaction conditions, the protocol is operationally simple and has also been demonstrated in a flow system. Electron paramagnetic resonance (EPR) investigations and density functional theory (DFT) calculations indicate that singlet oxygen is involved as the reactive oxygen species in this degradation process, which abstracts a hydrogen atom from a tertiary C–H bond, leading to hydroperoxidation and subsequent C–C bond cracking events via a radical process. Notably, our study indicates that an adduct of polystyrene and an acid catalyst might be formed in situ, which could act as a photosensitizer to initiate the formation of singlet oxygen. In addition, the oxidized polystyrene polymer may play a role in the production of singlet oxygen under light.

• Zhiliang Huang^a
• Muralidharan Shanmugam^b
• Zhao Liu^c
• Adam Brookfield^b
• Elliot L. Bennett^a
• Renpeng Guan^a
• David E. Vega Herrera^a
• Jose A. Lopez-Sanchez^a
• Anna G. Slater^a
• Eric J. L. McInnes^b
• Xiaotian Qi*^c
• Jianliang Xiao^a

• ^aDepartment of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
• ^bDepartment of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, U.K.
• ^cEngineering Research Center of Organosilicon Compounds & Materials, Ministry of Education, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China

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