Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
Department of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, U.K.
J Am Chem Soc. 2022 Apr 13;144(14):6532-6542. doi: 10.1021/jacs.2c01410. Epub 2022 Mar 30.
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 O. 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.
化学回收是最有前途的技术之一，可以通过为塑料废物提供解决方案来为循环经济目标做出贡献；然而，它仍处于早期发展阶段。在这项工作中，我们描述了第一个光驱动的、酸催化的协议，用于在 1 巴的 O 下将聚苯乙烯废物化学回收为有价值的化学品。该协议不需要光敏剂，只需要温和的反应条件，操作简单，并且已经在流动系统中得到了证明。电子顺磁共振（EPR）研究和密度泛函理论（DFT）计算表明，单线态氧作为反应性氧物种参与了这个降解过程，它从叔 C-H 键中提取一个氢原子，导致通过自由基过程发生过氧化物化和随后的 C-C 键断裂事件。值得注意的是，我们的研究表明，聚苯乙烯和酸催化剂的加成物可能在原位形成，它可以作为光敏剂来引发单线态氧的形成。此外，在光下，氧化的聚苯乙烯聚合物可能在产生单线态氧方面发挥作用。
