Reductive Defluorination of Branched Per- and Polyfluoroalkyl Substances with Cobalt Complex Catalysts
Reductive Defluorination of Branched Per- and Polyfluoroalkyl Substances with Cobalt Complex Catalysts
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DOI：
10.1021/acs.estlett.8b00122
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发表时间：
2018-05-01
影响因子：
10.9
通讯作者：
Strathmann, Timothy J.
中科院分区：
文献类型：
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作者：
Liu, Jinyong;Van Hoomissen, Daniel J.;Strathmann, Timothy J.
本研究探讨结构与反应性的关系，在支链全氟烷基和多氟烷基物质（PFASs）进行钴催化还原脱氢反应。实验结果和理论计算揭示了PFAS脱附程度、局部C-F成键环境和计算的键离解能之间的相关性。一般来说，溴化二苯醚的增加顺序如下：叔碳氟键<仲碳氟键<伯碳氟键。与三个氟化碳（或两个氟化碳和一个羧基）相邻的叔C-F键具有相对较低的BDE，允许发生初始脱附。生物钴卟啉络合物（B-12）和人工钴卟啉络合物（Co-PP）都被发现在选定的PFAS中催化脱氟多个C-F键。通常，Co-PP表现出比B-12更高的初始脱附速率。这两种复合物都没有在直链全氟辛酸（PFOA;没有叔碳氟键）或全氟烷基醚羧酸（叔碳氟溴化二苯醚含量过高）中产生显著的去氟作用。这些结果开辟了新的研究方向，包括（1）设计支化PFASs和钴配合物，促进PFASs在天然和工程系统中的完全脱附，以及（2）评估支化PFASs在存在B-12的生物系统中的潜在影响。
This study investigates structure-reactivity relationships within branched per- and polyfluoroalkyl substances (PFASs) undergoing cobalt-catalyzed reductive defluorination reactions. Experimental results and theoretical calculations reveal correlations among the extent of PFAS defluorination, the local C-F bonding environment, and calculated bond dissociation energies (BDEs). In general, BDEs increase in the following order: tertiary C-F bonds < secondary C-F bonds < primary C-F bonds. A tertiary C-F bond adjacent to three fluorinated carbons (or two fluorinated carbons and one carboxyl group) has a relatively low BDE that permits an initial defluorination to occur. Both a biogenic cobalt corrin complex (B-12) and an artificial cobalt-porphyrin complex (Co-PP) are found to catalytically defluorinate multiple C-F bonds in selected PFASs. In general, Co-PP exhibits an initial rate of defluorination that is higher than that of B-12. Neither complex induced significant defluorination in linear perfluorooctanoic acid (PFOA; no tertiary C-F bond) or a perfluoroalkyl ether carboxylic acid (tertiary C-F BDEs too high). These results open new lines of research, including (1) designing branched PFASs and cobalt complexes that promote complete defluorination of PFASs in natural and engineered systems and (2) evaluating potential impacts of branched PFASs in biological systems where B-12 is present.