文摘
Heteroatom-doped gold clusters have been of great interest to modify the catalytic performance of the clusters, although the structure–activity correlation is rarely discussed. Herein, we explore the catalytic activity of bimetallic gold-based MxAu25–x(SR)18 (M = Cu and Ag, and SR = SC2H4Ph) clusters and compare with that of homogold Au25(SR)18 in the CO oxidation reaction. It is found that the CeO2-supported clusters show catalytic activity for the reaction in the order CuxAu25–x(SR)18 > Au25(SR)18 > AgxAu25–x(SR)18. The supported clusters exhibit excellent catalytic activity and durability for prolonged conversion of CO into CO2 (98% in the case of CuxAu25–x(SR)18 at 120 °C for 110 h). Fourier-transform infrared (FT–IR) analyses as well as the density functional theory (DFT) calculations suggest that the thiolate ligands are partially removed under reaction conditions (T > 120 °C). The metal atoms thus exposed (Au, Ag, and Cu) are deemed as the catalytic active sites. DFT calculations suggest that metal exchange between the icosahedral core and the staple motif of the clusters at elevated temperature plays an important role on the conversion rate of CO oxidation. The adsorption of CO on the clusters would be more preferable to occur in the order Cu2Au23(SCH3)15 > Au25(SCH3)15 > Ag2Au23(SCH3)15, which is in line with the experimental results on the CO oxidation catalyzed by the bimetallic clusters.