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Photocatalytic low-temperature defluorination of PFASs
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Photocatalytic low-temperature defluorination of PFASs 全氟磺酸的光催化低温除氟 ▲ 作者：Hao Zhang, Jin-Xiang Chen, Jian-Ping Qu & Yan-Biao Kang ▲链接： https://www.nature.com/articles/s41586-024-08179-1 ▲摘要： 多氟烷基和全氟烷基物质（PFASs）存在于许多日常消费品中，通常是因为它们具有高热稳定性和化学稳定性，以及疏水和疏油特性。然而，赋予全氟辛烷磺酸特性的惰性碳氟（C-F）键也提供了通过除氟分解的抵抗力，导致其长期存在于环境和人体中，引起了重大的安全和健康问题。尽管最近在销毁功能化全氟辛烷的非焚烧方法方面取得了进展，但回收全氟碳化合物以及聚四氟乙烯等聚合全氟辛烷的工艺仅限于使用高温或强还原试剂的方法。 研究者报道了一种高度扭曲的咔唑核超光还原剂KQGZ对全氟烷的脱氟。在40℃ ~ 60℃的光催化条件下，一系列PFASs可被脱氟。聚四氟乙烯的主要产品是无定形碳和氟盐。全氟化合物、全氟辛烷磺酸、多氟辛酸等低聚全氟磺酸及其衍生物的脱氟产品为碳酸盐、甲酸盐、草酸盐和三氟乙酸盐。这样就可以将全氟磺酸中的氟作为无机氟化盐进行再循环。机理研究揭示了聚四氟乙烯和低聚全氟乙烯在反应行为和产物组分上的差异。 这项研究为“永久化学物质”全氟化合物的低温光还原除氟，特别是聚四氟乙烯，以及新的超光还原剂的发现打开了一扇窗。 ▲ Abstract： Polyfluoroalkyl and perfluoroalkyl substances (PFASs) are found in many everyday consumer products, often because of their high thermal and chemical stabilities, as well as their hydrophobic and oleophobic properties1. However, the inert carbon–fluorine (C–F) bonds that give PFASs their properties also provide resistance to decomposition through defluorination, leading to long-term persistence in the environment, as well as in the human body, raising substantial safety and health concerns. Despite recent advances in non-incineration approaches for the destruction of functionalized PFASs, processes for the recycling of perfluorocarbons (PFCs) as well as polymeric PFASs such as polytetrafluoroethylene (PTFE) are limited to methods that use either elevated temperatures or strong reducing reagents. Here we report the defluorination of PFASs with a highly twisted carbazole-cored super-photoreductant KQGZ. A series of PFASs could be defluorinated photocatalytically at 40–60?°C. PTFE gave amorphous carbon and fluoride salts as the major products. Oligomeric PFASs such as PFCs, perfluorooctane sulfonic acid (PFOS), polyfluorooctanoic acid (PFOA) and derivatives give carbonate, formate, oxalate and trifluoroacetate as the defluorinated products. This allows for the recycling of fluorine in PFASs as inorganic fluoride salt. The mechanistic investigation reveals the difference in reaction behaviour and product components for PTFE and oligomeric PFASs. This work opens a window for the low-temperature photoreductive defluorination of the ‘forever chemicals’ PFASs, especially for PTFE, as well as the discovery of new super-photoreductants. |
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