Efficient Aerobic Oxidation of Glucose to Gluconic Acid over Activated Carbon-Supported Gold Clusters.

The catalytic performance of the atomically precise gold cluster-Au38 (PET)24 (PET=2-phenylethanethiolate), immobilized on activated carbon (AC), was investigated for the aerobic oxidation of glucose to gluconic acid. The Au38 (PET)24 /AC-120 catalysts, annealed at 120 °C in air, exhibited high catalytic activity and significantly better performance than the corresponding catalysts Au38 /AC-150 and Au38 /AC-300 (treated at 150 and 300 °C to remove the protecting thiolate ligands). The high activity of the robust Au cluster was a result of the partial ligand removal, providing catalytically active sites, which were evidenced by TEM, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier-transform IR spectroscopy. Au38 (PET)24 /AC-120 also showed excellent recyclability (up to seven cycles). The turnover frequency for the Au38 (PET)24 /AC-120 catalyst was 5440 h-1 , which is higher than for the Pd/AC, Pd-Bi/AC, and Au/AC under identical reaction conditions. This new ultra-small gold nanomaterial is expected to find wide application in other catalytic oxidations.