Thermal control of the defunctionalization of supported Au₂₅(glutathione)₁₈ catalysts for benzyl alcohol oxidation

Abstract

Au25(SG)18 (SG – glutathione) clusters deposited on ZrO2 nanoparticles have been used as a catalyst for benzyl alcohol oxidation. Calcination was performed at different temperatures to study the ligand and particle size effect on the catalytic activity. In contrast to most gold nanoclusters which have to be completely defunctionalized for maximum catalytic activity, the partially defunctionalized Au25(SG)18@ZrO2 catalyst, thermally treated at 300 °C, exhibits full conversion of benzyl alcohol within 15 h under atmospheric pressure with 94% selectivity towards benzaldehyde.

Study of the oxidative esterification of furfural catalyzed by Au25(glutathione)18 nanocluster deposited on zirconia

“…The material was prepared as previously reported [15]. ZrO 2 obtained from calcination of Zr(OH) 4 (550 °C, 12 h) was wet-impregnated with a water solution of Au 25 (SG) 18 clusters to give a material with a theoretical loading of 1 wt% of Au.…”

“…Au 25 (SG) 18 /ZrO 2 catalysts were prepared as described in the Experimental section following previous report [15], and contain 1 wt% of Au before calcination steps. Thermogravimetric analyses on the Au 25 (SG) 18 clusters indicate that calcination at 200, 300 and 400 °C led to 36, 75 and 100% loss of ligand, respectively [15].…”

“…Au 25 (SG) 18 /ZrO 2 catalysts were prepared as described in the Experimental section following previous report [15], and contain 1 wt% of Au before calcination steps. Thermogravimetric analyses on the Au 25 (SG) 18 clusters indicate that calcination at 200, 300 and 400 °C led to 36, 75 and 100% loss of ligand, respectively [15]. As an additional characterization for the present work, XPS studies of Au indicate here that the oxidation state of Au changed upon calcination (Figure 1) [22].…”

“…We recently reported the efficiency for simple benzyl alcohol oxidation into benzaldehyde of a new composite material, Au 25 (SG) 18 gold thiolate nanocluster (SG standing for glutathione) supported on ZrO 2 [15]. The use of atomically well-defined Au nanoclusters as catalysts has been recently introduced and the ligands around the cluster play definitively a role in the reactivity even for liquid phase catalysis [16][17][18].…”

Advanced hybrid nanomaterials

“…Finally, catalysis is the focus of an article reporting the performance of functionalized gold clusters deposited on ZrO 2 nanoparticles for benzyl alcohol oxidation in [39]. Interestingly, the defunctionalized gold nanoclusters exhibit full catalytic conversion.…”