(403d) Enhancing Polystyrene Upcycling through Sbsi Chalcohalides-Driven Photocatalysis: A Novel Approach to Combat Plastic Waste

Plastic waste management remains a critical environmental challenge. Since 1950, over 6.3 billion tons of plastic have been produced, with more than 80% ending up in landfills or polluting the natural environment [1]. Polystyrene (PS) consumer products worsen this issue due to their extensive applications and remarkably short lifecycle. Given the rising demand for these materials and their difficulty to be recycled, there is an interest in employing photocatalysis as a sustainable method to depolymerize PS into valuable products [2]. Nevertheless, the application of conventional semiconductor photocatalysts in PS upcycling has been limited due to wide bandgaps and charge recombination.

Chalcohalides, a novel family of inorganic semiconductors, emerges as a promising solution. These materials feature highly dispersive band edges that facilitate efficient charge transfer and exhibit narrow bandgaps [3]. Also, the presence of divalent chalcogen and monovalent halide anions in these materials provides enhanced defect tolerance.

This study demonstrates that SbSI chalcohalide can generate singlet oxygen (¹O₂), a potent, non-radical reactive oxygen species. ¹O₂ possesses a high energy (~94 kJ/mol) compared to ground-state O₂, enabling it to abstract hydrogen from the stable benzylic C(sp³)−H bond in PS [4]. This initiates degradation of PS into valuable oxygenated products such as benzaldehyde and acetophenone under mild reaction conditions. Preliminary experiments with PS dimer model compound (1,3-diphenylpropane) showed 28.37% C₇-product yield with ~80% selectivity towards benzaldehyde. Detailed experimental results focusing on the reaction mechanism, supported by catalyst characterization, Electron Paramagnetic Resonance (EPR) spectroscopy, and untargeted Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MS/MS) analysis will be presented at the conference.

References

[1] Alabi, O. A., Ologbonjaye, K. I., Awosolu, O., & Alalade, O. E. (2019). Public and environmental health effects of plastic wastes disposal: a review. J Toxicol Risk Assess, 5(021), 1-13.

[2] Ghalta, R., Bal, R., & Srivastava, R. (2023). Metal-free photocatalytic transformation of waste polystyrene into valuable chemicals: advancing sustainability through circular economy. Green Chemistry, 25(18), 7318-7334.

[3] Ran, Z., Wang, X., Li, Y., Yang, D., Zhao, X. G., Biswas, K., ... & Zhang, L. (2018). Bismuth and antimony-based oxyhalides and chalcohalides as potential optoelectronic materials. npj Computational Materials, 4(1), 14.

[4] Huang, Z., Shanmugam, M., Liu, Z., Brookfield, A., Bennett, E. L., Guan, R., ... & Xiao, J. (2022). Chemical recycling of polystyrene to valuable chemicals via selective acid-catalyzed aerobic oxidation under visible light. Journal of the American Chemical Society, 144(14), 6532-6542.