Selectivity Regulation in Au-Catalyzed Nitroaromatic Hydrogenation by Anchoring Single-Site Metal Oxide Promoters

Abstract

Precise control of selectivity in hydrogenation reactions is a long-standing challenge. Surface decoration of nanocatalysts with transition-metal oxide nanoparticles (NPs) is an effective strategy to tailor the catalytic selectivity but generally at the expense of activity due to the blocking of active sites. Here, we report that constructing single-site metal oxide modifiers (NiO, CoO x , or FeO x ) on supported Au NPs by atomic layer deposition (ALD) can regulate their catalytic selectivity for nitroaromatic hydrogenation. The coverage of single-site metal oxide can be precisely tuned by altering the number of ALD cycles. The Au/TiO2 decorated with five cycles of NiO (Ni: 0.32 wt %) in the style of a single site can efficiently change the product selectivity from azo to azoxy compounds without significantly blocking the surface active sites. The density functional theory calculations indicate that the azoxybenzene bonded to the single-site NiO-decorated Au(111) with a larger adsorption energy, which inhibits the overhydrogenation of azoxybenzene and results in high azoxybenzene selectivity. Our work has demonstrated a general and efficient way to regulate the reaction selectivity of metal nanocatalysts by anchoring single-site metal oxide promoters.

Modifying electron injection kinetics for selective photoreduction of nitroarenes into cyclic and asymmetric azo compounds

“…Noted that the commercial azo dyestuffs were commonly prepared via the well-known diazotization method using diazonium salts as reaction intermediates 32 , 33 and recent advances demonstrated several one-pot procedures for reductive condensation of nitroarenes into aromatic azo compounds 34 – 38 . However, reductive coupling of two different nitroarenes into one asymmetric azo compound remains challenging, due to the difficult to preclude competing reactions between the azanol and nitroso species with the same aromatic groups from the condensation reactions between the azanol and nitroso species having different aromatic groups.…”

Atomic Design and Fine-Tuning of Subnanometric Pt Catalysts to Tame Hydrogen Generation

“…Atomic layer deposition (ALD) is considered to be an ideal method to accurately construct metal subnanocatalysts with tunable atom numbers due to its self-limiting, atom-by-atom growth and the ample scope of materials that can be deposited. [21][22][23][24] However, the successful examples for preparing subnanocatalysts with controllable atom numbers through ALD (single atom and cluster) is still very limited, mainly due to the strong tendency of migration and aggregation of metal species during the ALD process.…”

Single-Atom Catalysts for Thermal Heterogeneous Catalysis in Liquid: Recent Progress and Future Perspective

“…Schematic illustration of the hydrogenation of nitrobenzene to azo or azoxy products. Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

“…45 For different substituted nitrobenzene, the selectivity to azoxy compounds (∼90 %) with Co 1 /G SACs was much higher than those of Pt/ Very recently, Qin's group reported that in the reduction coupling of nitroarenes, the catalytic selectivity was changed from azo to azoxy with single-site transition metal oxides modified Au-based nanocatalysts (Figure 4). 46 Generally, azoxy is thermodynamically unfavorable compared to azo. However, the adsorption energy of azoxybenzene on single-site NiO decorated Au(111) is larger.…”