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. They were supported 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 the stability of the catalysts.