Selective Oxidation of Aliphatic Alcohols using Molecular Oxygen at Ambient Temperature: Mixed-Valence Vanadium Oxide Photocatalysts

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• 作者：Sifani Zavahir ; Qi Xiao ; Sarina Sarina ; Jian Zhao ; Steven Bottle ; Mark Wellard ; Jianfeng Jia ; Liqiang Jing ; Yiming Huang ; James P. Blinco ; Haishun Wu ; Huai-Yong Zhu
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：June 3, 2016
• 年：2016
• 卷：6
• 期：6
• 页码：3580-3588
• 全文大小：530K
• 年卷期：0
• ISSN：2155-5435

文摘

Here we report a class of photocatalysts: mixed-valence vanadium oxide particles grafted onto a variety of oxide supports. In these catalysts V₆O₁₃ species with mixed oxidation states (V⁴⁺ or V⁵⁺) are believed to be catalytically active sites. These catalysts successfully enable alcohol oxidation to selectively produce aldehydes and ketones using O₂ as the oxidant. The catalytic process is driven by visible light irradiation at room temperature and, most importantly, progresses with negligible overoxidation. The catalysts can even selectively oxidize aliphatic alcohols, which are much more challenging to control in comparison to aromatic analogues. They can also be applied to the activation and oxidation of the otherwise stable C–H bonds of saturated aromatic hydrocarbons, such as toluene and xylene, under irradiation. Both experimental results and density functional theory (DFT) simulations suggest the formation of V₆O₁₃-alkoxide species as the initial step in the catalytic cycle. The V₆O₁₃-alkoxide then acts as the light harvester, being excited by light of wavelength shorter than 550 nm. Facile room-temperature C–H bond cleavage in the excited state V₆O₁₃-alkoxide in the presence of O₂ leads to the carbonyl-containing products. These findings demonstrate an example of light-driven selective oxidation of diverse alcohols via in situ formation of photoresponsive V₆O₁₃-alkoxide species. This catalytic process is especially valuable for the synthesis of temperature-sensitive products and represents an alternative pathway to many conventional thermal oxidation reactions.