Transition metal-mediated catalytic properties of gold nanoclusters in aerobic alcohol oxidation

Heteroatom dopants can greatly modify the electronic and physical properties and catalytic performance of gold nanoclusters. In this study, we investigate the catalytic activity of [Au25-x (PET)(18-x) M]NH3 (PET = 2-phenylethanethiolate, and M = Cu, Co, Ni, and Zn)nanoclusters in aerobic alcohol oxidation. The [Au25-x (PET)(18-x) M]NH3 nanoclusters are thoroughly characterized by matrix assisted laser desorption ionization (MALDI)mass spectrometry, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and inductively coupled plasma-mass spectrometry (ICP-MS). The XPS analyses suggest that the transition metals strongly interact with the gold atoms of the nanoclusters. The CeO2-supported nanoclusters show catalytic activity, based on the conversion of benzyl alcohol, in the order, [Au25-x (PET)(18-x) Ni] > [Au25-x (PET)(18-x) Cu] > [Au25-x (PET)(18-x) Zn] > [Au25-x (PET)(18-x) Co]. Regarding product selectivity, the [Au25-x (PET)(18-x) Zn] and [Au25-x(PET)(18-x)Co] catalysts preferably yield benzaldehyde, [Au25-x (PET)(18-x) Cu] yields benzaldehyde and benzyl acid, and [Au25-x (PET)(18-x) Ni] yields benzyl acid. The exposed metal atoms are considered as the catalytic active sites. Also, the catalytic performance (including activity and selectivity)of the [Au25-x (PET)(18-x) M] catalysts is greatly turned and mediated by the transition metal type.