Synergistic Effect of Ligand-Cluster Structure and Support in Gold Nanocluster Catalysts for Selective Hydrogenation of Alkynes

Abstract

In the field of nanocluster catalysis, it is crucial to understand the interplay of different parameters, such as ligands, support and pretreatment and their effect on the catalytic process. In this study we chose the selective hydrogenation of phenylacetylene as a model reaction and employed two gold nanoclusters as catalysts, the phosphine protected Au11 and the thiolate protected Au25, each with different binding motifs and supported them on MgO, Al2O3 and a hydrotalcite (HT), chosen for their different acidity. We found that while in the case of the Au11 MgO was the preferred support and the pretreatment had a positive impact on the catalysis, for the Au25 the HT performed best and pretreating had negative effects, indicating that the bonding motif of the ligands and their interaction with the support is crucial for the catalytic process. Using X-Ray absorption spectroscopy we could trace these phenomena to changes in the cluster-ligand interface, which seem to impact on the stability of the catalysts.