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专业: 光化学和辐射化学

[交流] 采用同位素标记法探测TiO2光催化体系水相降解苯环开环机理

中科院北京化学所赵进才院士最近JACS ——采用同位素标记法探测TiO2光催化体系水相降解苯环开环机理
Determining the TiO2‑Photocatalytic Aryl-Ring-Opening Mechanism
in Aqueous Solution Using Oxygen-18 Labeled O2 and H2O

采用同位素标记O2，H2O，一对叔丁基邻苯二酚为模型，在TiO2，水：乙腈=1:1比例溶剂中，研究芳香环开环产物。
首次获得了分子氧O2中O原子插入苯环C-C键的直接证据。这说明了分子氧O2是芳香烃开环的反应剂。

The molecules O2 and H2O dominate the cleavage of aromatic sp2 C −C bonds, a crucial step in the degradation
of aromatic pollutants in aqueous TiO2 photocatalysis, but their precise roles in this process have remained elusive.
This can be attributed to the complex oxidative species involved and to a lack of available models for reactions
with a high yield of direct products. Here, we used oxygen-18 isotope labeled O2 and H2O to observe the aromatic
ring-opening reaction of the model compound 3,5-di-tert-butylcatechol(DTBC), which was mediated by TiO2
photocatalysis in an aqueous acetonitrile solution. By analyzing the primary intermediate products ( ～75% yield),
especially the seven-membered ring anhydrides that were formed, we obtained direct evidence for the oxygen
atom of dioxygen insertion into a C −C bond of the aromatic ring. This indicates that molecular oxygen is the ultimate
ring-opening agent in TiO2 photocatalysis and that it undergoes single O atom incorporation rather than the previously
proposed molecular oxygen 1,2-addition processes. The ratio of intradiol to extradiol products depends on the particle
size of TiO2 catalysts used, which suggests that the O2 activation is correlated with the available coordination sites on
the TiO2 surface in the photocatalytic cleavage of the aromatic ring.

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