Synthesis of active, robust and cationic Au25 cluster catalysts on double metal hydroxide by long-term oxidative aging of Au25(SR)18

摘要

Synthesis of an atomically precise Au25 cluster catalyst was attempted by long-term, low-temperature aging of Au25(BaET)18 (BaET-H = 2-(Boc-amino)ethanethiol) on various double metal hydroxide (DMH) supports. X-ray absorption fine structure analysis revealed that bare Au25 clusters with high loading (1 wt%) were successfully generated on the DMH containing Co and Ce (Co3Ce) by oxidative aging in air at 150 °C for >12 h. X-ray absorption near-edge structure and X-ray photoelectron spectroscopies showed that the Au25 clusters on Co3Ce were positively charged. The Au25/Co3Ce catalyst thus synthesized exhibited superior catalytic performance in the aerobic oxidation of benzyl alcohol under ambient conditions (TOF = 1097 h−1 with >97% selectivity to benzoic acid) and high durability owing to a strong anchoring effect. Based on kinetic experiments, we propose that abstraction of hydride from α-carbon of benzyl alkoxide by Au25 is the rate-determining step of benzyl alcohol oxidation by Au25/Co3Ce.