Catalytic oxidation of polystyrene to aromatic oxygenates over a graphitic carbon nitride catalyst

Ruochen Cao; Mei-Qi Zhang; Chaoquan Hu; Dequan Xiao; Meng Wang; Ding Ma

doi:10.1038/s41467-022-32510-x

Catalytic oxidation of polystyrene to aromatic oxygenates over a graphitic carbon nitride catalyst

Nat Commun. 2022 Aug 16;13(1):4809. doi: 10.1038/s41467-022-32510-x.

Authors

Ruochen Cao¹, Mei-Qi Zhang¹, Chaoquan Hu^{2

3}, Dequan Xiao⁴, Meng Wang⁵, Ding Ma⁶

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, People's Republic of China.
² State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China.
³ Nanjing IPE Institute of Green Manufacturing Industry, Nanjing, 211135, People's Republic of China.
⁴ Center for Integrative Materials Discovery, Department of Chemistry and Chemical and Biomedical Engineering, University of New Haven, West Haven, CT, 06516, USA.
⁵ Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, People's Republic of China. m.wang@pku.edu.cn.
⁶ Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, People's Republic of China. dma@pku.edu.cn.

Abstract

The continuous increase in manufacturing coupled with the difficulty of recycling of plastic products has generated huge amounts of waste plastics. Most of the existing chemical recycling and upcycling methods suffer from harsh conditions and poor product selectivity. Here we demonstrate a photocatalytic method to oxidize polystyrene to aromatic oxygenates under visible light irradiation using heterogeneous graphitic carbon nitride catalysts. Benzoic acid, acetophenone, and benzaldehyde are the dominant products in the liquid phase when the conversion of polystyrene reaches >90% at 150 °C. For the transformation of 0.5 g polystyrene plastic waste, 0.36 g of the aromatic oxygenates is obtained. The reaction mechanism is also investigated with various characterization methods and procedes via polystyrene activation to form hydroxyl and carbonyl groups over its backbone via C-H bond oxidation which is followed by oxidative bond breakage via C-C activation and further oxidation processes to aromatic oxygenates.