A Molecular Mechanism for the Chemoselective Hydrogenation of Substituted Nitroaromatics with Nanoparticles of Gold on TiO2 Catalysts: A Cooperative Effect between Gold and the Support

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• 作者：Mercè ; Boronat ; Patricia Concepció ; n ; Avelino Corma ; Silvia Gonz&aacute ; lez ; Francesc Illas ; Pedro Serna
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：December 26, 2007
• 年：2007
• 卷：129
• 期：51
• 页码：16230 - 16237
• 全文大小：824K
• 年卷期：v.129,no.51(December 26, 2007)
• ISSN：1520-5126

文摘

Nanoparticles of gold on TiO₂ are highly chemoselective for the reduction of substitutednitroaromatics, such as nitrostyrene. By combining kinetics and in situ IR spectroscopy, it has been foundthat there is a preferential adsorption of the reactant on the catalyst through the nitro group. IR studies ofnitrobenzene, styrene, and nitrostyrene adsorption, together with quantum chemical calculations, showthat the nitro and the olefinic groups adsorb weakly on the Au(111) and Au(001) surfaces, and that althougha stronger adsorption occurs on low-coordinated atoms in gold nanoparticles, this adsorption is not selective.On the other hand, an energetically and geometrically favored adsorption through the nitro group occurson the TiO₂ support and in the interface between the gold nanoparticle and the TiO₂ support. Suchpreferential adsorption is not observed with nanoparticles of gold on silica which, contrary to the Au/TiO₂catalyst, is not chemoselective for the reduction of substituted nitroaromatic compounds. Therefore, thehigh chemoselectiviy of the Au/TiO₂ catalyst can be attributed to a cooperation between the gold nanoparticleand the support that preferentially activates the nitro group.