Benzyl Alcohol Oxidation Using Gold Catalysts Derived from Au8 Clusters on TiO2

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, Au-8(PPh3)(8)(NO3)(2) onto anatase-phase TiO2 nanoparticles. The catalysts were then calcined under two different conditions: O-2 (Au-8/TiO2:O-2) and O-2 followed by H-2 (Au-8/TiO2:O-2-H-2) at 200 degrees C, to dislodge phosphine ligands from the Au core. It was found that Au-8/TiO2:O-2-H-2 catalyst showed a decent catalytic activity in benzyl alcohol oxidation while Au-8/TiO2 and Au-8/TiO2:O-2 were completely inactive. Such results imply that small-size gold clusters (2-3nm) 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. [GRAPHICS] .