Benzyl Alcohol Oxidation Using Gold Catalysts Derived from Au8 Clusters on TiO2
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Atomically-precise gold clusters have gained attraction in catalysis due to high fraction of low-coordinated gold atoms, unique structural geometry and ligand effect. Phosphine-ligated gold clusters offer an advantage in the light of the labile gold-phosphorous bond for easy ligand removal. Here, heterogeneous gold catalysts were prepared by depositing atomically-precise phosphine-ligated gold clusters, Au8(PPh3)8(NO3)2 onto anatase-phase TiO2 nanoparticles. The catalysts were then calcined under two different conditions: O2 (Au8/TiO2:O2) and O2 followed by H2 (Au8/TiO2:O2–H2) at 200 °C, to dislodge phosphine ligands from the Au core. It was found that Au8/TiO2:O2–H2 catalyst showed a decent catalytic activity in benzyl alcohol oxidation while Au8/TiO2 and Au8/TiO2:O2 were completely inactive. Such results imply that small-size gold clusters (2–3 nm) alone do not always contribute to high catalytic activity of gold catalysts. It is suggested that the presence of NO3− species defines the catalytic activity of supported gold clusters in benzyl alcohol oxidation in the case of these catalysts and reinforces our initial claim in the previous work.
KeywordsHeterogeneous catalysis Alcohols Oxidation Green chemistry
The authors would like to thank Professor Milo Kral and Mike Flaws for their help with HRTEM imaging, Dr. Meike Holzenkaempfer and Dr. Marie Squire for development of the HPLC methodology. This work was supported by the MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury.
- 23.Zhu Y, Qian H, Jin R (2010) Chemistry A 16:11455–11462Google Scholar