Nanostructured Ni-MoCx: An efficient non-noble metal catalyst for the chemoselective hydrogenation of nitroaromatics

Abstract

Catalysts for chemoselective hydrogenation are of vital importance for the synthesis of various important chemicals and intermediates. Herein we developed a simple method for preparing a highly efficient Ni-MoCx nanocomposite catalyst via temperature-programmed carburization of a polyoxometalate precursor. X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) analyses indicate that the resulting mesoporous nanocomposite catalyst is made up of well-dispersed metallic nickel particles embedded in a MoCx matrix. This catalyst exhibits high activity and selectivity (> 99%) in the hydrogenation of various substituted nitroaromatics to corresponding anilines. The high efficiency is attributed to the intimate contact of the constituents favoring electron transfer and hydrogen adsorption. Dihydrogen is physisorbed on the carbide support and dissociates on the nickel particles, as evidenced by Mo K-edge X-ray absorption near-edge structure (XANES) spectra, density functional theory (DFT), and hydrogen—deuterium exchange. The remarkable catalytic performance of the catalyst could be traced back to the synergistic interaction between the Ni particles and the carbide support. In-situ infrared spectroscopy and DFT simulations indicated that the adsorption/activation of the nitro group is favored compared to that of other substituents at the aromatic ring. In recyclability tests, the Ni-MoCx nanocomposite showed no significant loss of catalytic performance in seven consecutive runs, indicating its robust nature.

Robust 2 nm-sized gold nanoclusters on Co3O4 for CO oxidation

“…4c, the activity of the Au/Co 3 O 4 catalysts was dropped from 2.92 to 1.87 mol reacted CO g Au −1 s −1 during the 12 h reaction in the CO oxidation (red line). While, Au/Co 3 O 4 gave a stable activity performance of 5.26–5.39 mol reacted CO g Au −1 s −1 during the test (9 h, black line), which is higher than the reported value over the oxide-supported gold NCs catalysts, as shown in Table S1 † 8–12 . Overall, the results indicated that Au/Co 3 O 4 catalysts exhibited excellent durability for CO oxidation.…”

“…Reducible oxides, such as Fe 2 O 3 , TiO 2 , CeO 2 , and Co 3 O 4 , often exhibit exceptionally high activity for CO oxidation, when they are used to support gold nanoparticles. 8–14 This is primarily because these oxides could create oxygen vacancies on their surfaces close to the Au particles, forming strong metal-support interactions (SMSI). In this context, Au/Co 3 O 4 catalyst has attracted particular attention because of their exceptionally high activities for low-temperature CO oxidation.…”

Efficient Catalytic Hydrogenation of Glucose to Sorbitol over Metallic Nickel-Rich Nickel Borides under Mild Reaction Conditions

“…As the glucose-to-sorbitol transformation only involves a single catalytic hydrogenation process, the activation of a hydrogen molecule over the catalyst should play an important role in its catalytic performance, which can be well illustrated by the H 2 -TPD technique. As presented in Figure d, a clear peak could be noticed at around 100 °C in all of the samples, representing the desorption of adsorbed [H] species over the Ni borides. , This temperature is similar to the reaction temperature, indicating the good capability of the Ni borides toward the adsorption of the hydrogen molecule at a relatively low temperature. Interestingly, with the increase in the KH 2 PO 4 amount from 0 to 10 mmol, the desorption amount of the [H] species greatly increased from 27.9 to 93.2 μmol/g, which demonstrated the enhanced hydrogen adsorption ability of the catalyst.…”

Atomically Precise Metal Nanocluster Photosystem: Electron Relay Boosts Photocatalytic Organic Transformation

“…In the past few decades, metal nanoparticles (NPs) have ranked an important status among nanomaterials and have been widely used in various catalysis . When the size of metal NPs is reduced to a few or hundreds of atoms with a diameter of less than 2 nm, they are defined as atomically precise metal nanoclusters (NCs) that are completely different from traditional metal NPs in terms of their physicochemical properties and electronic structure. , More specifically, atomically precise metal NCs demonstrate discrete energy band structures, which endows them with a molecular-like highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, featuring potential light harvesting antennas. − Moreover, peculiar atomic stacking fashion, quantum confinement effect, and enriched active sites of metal NCs make them applicable alternatives for multifarious photoredox catalysis. , However, photoinduced oxidative agglomeration of metal NCs results in the poor stability, considerably reducing the photosensitization effect of metal NCs and hinders their emerging applications in photoredox catalysis. − Therefore, how to rationally maneuver the instability of metal NCs is crucial to develop robust and durable metal NC photosystems.…”