Producing of cinnamyl alcohol from cinnamaldehyde over supported gold nanocatalyst

Chemoselective hydrogenation of unsaturated aldehyde to unsaturated alcohol has attracted growing interests in recent years due to its widespread applications in fine chemicals. However, the hydrogenation of the C=O bond was thermodynamically and kinetically unfavorable over the hydrogenation of the C=C bond. Thus, to obtain the unsaturated alcohol from the unsaturated aldehyde is very difficult in most of the catalytic systems. In this work, ZnAl-hydrotalcite-supported cysteine-capped Au25 nanoclusters were used as the precatalysts for chemoselective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The catalyst showed stable high selectivity (~ 95%) at prolonged reaction time and complete conversion of the substrate. According to the results of the control experiments, the in-situ DRIFTS of the substrate under high pressure of hydrogen and the 27Al MAS-NMR spectroscopy, we proposed that the difference of the preferential adsorption of the C=O bond to that of the C=C bond was derived from the nature of the support of the gold catalysts.