ZnAl‐Hydrotalcite‐Supported Au₂₅Nanoclusters as Precatalysts for Chemoselective Hydrogenation of 3‐Nitrostyrene

Abstract

Chemoselective hydrogenation of 3-nitrostyrene to 3-vinylaniline is quite challenging because of competitive activation of the vinyl group and the nitro group over most supported precious-metal catalysts. A precatalyst comprised of thiolated Au nanoclusters supported on ZnAl-hydrotalcite yielded gold catalysts of a well-controlled size (ca. 2.0 nm)-even after calcination at 500 °C. The catalyst showed excellent selectivity (>98 %) with respect to 3-vinylaniline, and complete conversion of 3-nitrostyrene over broad reaction duration and temperature windows. This result is unprecedented for gold catalysts. In contrast to traditional catalysts, the gold catalyst is inert with respect to the vinyl group and is only active with regard to the nitro group, as demonstrated by the results of the control experiments and attenuated total reflection infrared spectra. The findings may extend to design of gold catalysts with excellent chemoselectivity for use in the synthesis of fine chemicals.

Rh Doping in Pd Nanocubes Optimizes the Adsorption of 3‐Nitrostyrene towards Selective Hydrogenation of Vinyl Group

“…Specially, preferential attack of the C=C group gives 3nitroethylbenzene, while the hydrogenation of both C=C and NO 2 groups yields 3-ethylbenzenamine. [19] Notably, the produced 3-aminostyrene from the selective reduction of NO 2 group was lower than detection limit for all catalysts. When a blank reaction without catalyst was carried out, all products were below the detection limit (Table S2) The introduction of Rh atoms into Pd nanocubes dramatically increased the selectivity for 3-nitroethylbenzene.…”

“…In a model reaction, the reaction was conducted in 0.5 mmol of 3‐nitrostyrene dissolved in ethanol solvent over 0.1 mg of catalyst under 1 atm of H 2 at 25 °C for 4 h. Figure a showed the schematic diagram for hydrogenation of 3‐nitrostyrene. Specially, preferential attack of the C=C group gives 3‐nitroethylbenzene, while the hydrogenation of both C=C and NO 2 groups yields 3‐ethylbenzenamine . Notably, the produced 3‐aminostyrene from the selective reduction of NO 2 group was lower than detection limit for all catalysts.…”

Metal-Support Synergy of Supported Gold Nanoclusters in Selective Oxidation of Alcohols

“…To this end, it is desirable to separate these factors. In this work, the atomically precise Au 25 NCs were synthesized by the NaOH-mediated NaBH 4 reduction method according to our previous work [37,38]. Thus, the effect of the preparation method or size effect might be ignored in some aspects.…”

“…Based on the previous study [15], the calcination temperature of 300 • C might not be enough to transform the hydrotalcite into the complete magnesium oxides, while, at this temperature, the MgAl-hydrotalcite supported gold catalysts could display good performances in different reactions [15,38]. In addition, the gold catalysts calcined at the same temperature was imperative for comparison of the different gold catalysts, since the size distribution largely depends on the heat treatment temperature [32,37]. Subsequently, Figure 2d shows the intact phase structure of MgO, which maintained the originate state of the supports.…”

Enhancing Light-Driven Production of Hydrogen Peroxide by Anchoring Au onto C3N4 Catalysts

“…The activity is closely related to the size of the noble metal nanoparticles. Generally, when the size of the metal particles is greater than 7 nm, the activity drops sharply [31]. However, the smaller-sized metal particles possess a low Tammann temperature and high surface energy, leading to low thermal stability and the sintering phenomenon when heated [32].…”