Hydrogenation Of Nitroarenes Research Articles

Enhanced catalytic performance of B-doped SiC supported Ni catalysts for the hydrogenation of nitroarenes

SiC and B-doped SiC were prepared and employed to support Ni components for the catalytic hydrogenation of nitroarenes. The B-doping of SiC evidently improved the catalytic activity of Ni/SiC, and the activity of Ni/SiC-B0.5 catalyst was 2.4 times higher than that of undoped Ni/SiC. Further investigations revealed that the incorporation of B substituted some Si atoms in SiC lattice and thus produced carbon vacancies. These vacancies will result in a heterogeneous distribution of surface charges on SiC, thereby enhancing the adsorption and activation of nitroarenes on the support surface. In addition, the carbon vacancies can also act as donor centers for capturing dissociated hydrogen species, thus enhancing the hydrogen spillover from Ni to SiC surface.

Chemoselective Transfer Hydrogenation of Nitroarenes with Ammonia Borane Catalyzed by Copper N‐heterocyclic Carbene Complexes

Comprehensive SummaryHerein, we present a method for the homogeneous hydrogenation of nitroarenes to produce anilines using low catalyst loading (1 mo%) of copper N‐heterocyclic carbene complexes as the catalyst and ammonia borane as the source of hydrogen. A wide range of nitroarenes, featuring diverse functional groups, were selectively transformed into their corresponding primary aromatic amines with high yields. This process can be readily scaled up and exhibits compatibility with various sensitive functional groups, including halogen, trifluoromethyl, aminomethyl, alkenyl, cyano, ester, amide, and hydroxyl. Notably, this catalytic methodology finds application in the synthesis of essential drug compounds. Mechanistic investigations suggest that the in‐situ‐generated Cu‐H species may serve as active intermediates, with reduction pathways involving species such as azobenzene, 1,2‐diphenylhydrazine, nitrosobenzene, and N‐phenylhydroxylamine.

Zeolitic Pickering Emulsifier with Intrinsic Amphiphilicity.

The formation of oil-in-water Pickering emulsions stabilized by lamellar zeolite MWW (International Zeolite Association, three-letters code) emulsifier without surface grafting is investigated. The crucial emulsification factors are the oligolayer morphology and amphiphilicity developed upon acidic treatment (NH4+ exchange/calcination, HNO3 treatment). In contrast with the readily available/abundant hydrophilic ≡Si-OH group in layer MWW, the lipophilicity generated by strong acid sites is another key to the success of emulsification. Hydrocarbon-strong acid site interaction is long known in petrochemistry and superacid research. However, to the best of our knowledge, this interaction was first introduced to gain lipophilicity in emulsion formation. Finally, the Pd-loaded acidic form of the MWW zeolite successfully stabilized the toluene/H2O emulsion system. The biphasic interfacial nitroarene hydrogenation demonstrated excellent catalytic performance. Overall, this work provided not only a new kind of intrinsic solid to emulsify the organic-aqueous biphase system but also a new mechanism to generate lipophilicity. Both are important for the applications and designs of Pickering emulsion materials.

Multi-functional hydrogen- and oxygen-capturing FeCo-N-C catalyst with improved hydrogenation of nitroarenes and ORR activity

Hydrogen energy storage and transportation are critical issues that must be addressed to ensure the development of alternatives to fossil fuel energy in the future. Herein, the poly(Schiff base) strategy is used to explore the carbon substrate, which is enclosed with binary metal Fe and Co as precursors. After the calcination and acid treatment steps, one of the FeCo alloy, termed FeCoNC-1000A900, was assembled with porous carbon skeleton as a shell and enclosed with FeCo alloy as a core. The FeCoNC-1000A900 exhibits outstanding H2 capture properties from NaBH4/EtOH mixtures circumstance owing to its large average particle size of 45 nm and high specific surface area of 462.07 m2/g. Notably, the FeCoNC-1000A900 acquires bi-functional catalysis efficacy, one is for chemoselectivity in the hydrogenation of nitroarene substrates and shows a high turnover frequency in 690 h−1 within the overall conversion yield. The other one is the O2 capture performance toward the oxygen reduction reaction with the excellent onset potential of 0.89 V, the half-wave potential of 0.77 V, and limiting current density of − 5.56 mA cm−2, which are comparable to those of the commercial Pt/C catalyst. In addition, the Tafel slope of 79.6 mV dec−1 is lower than those for other catalysts. Consequently, the development of the novel FeCoNC-1000A900 catalyst has two functional applications.

Mechanism and Kinetics Guided Design of Catalysts for Functionalized Nitroarenes Hydrogenation

AbstractSelective hydrogenation of functionalized nitroarenes to anilines employed with heterogeneous catalysts is a significant process and widely applied in chemical industry. However, designing high‐performance catalysts for these processes remains challenging. Recently, notable advancements have been achieved in synthesis methodologies, characterization techniques, and theoretical calculations, offering opportunities to gain insights into mechanisms. This review summarizes the recent progress in understanding the mechanistic aspects of selective hydrogenation catalysis for functionalized nitroarenes. We initiate by delving into the structure‐performance relationship, with the aim of providing a comprehensive understanding of mechanistic and kinetic details in the selective hydrogenation of functionalized nitroarenes. Subsequently, we introduce various strategies for designing high‐performance catalysts, categorizing them into three key aspects: isolating active sites, synergizing active sites and regulating local environments of active sites. Finally, we conclude with a concise overview of the current state of this field and provide a forward‐looking perspective for future studies, emphasizing the high‐performance design and manipulation of catalysts to achieve precise control over selectivity towards target products.

Pd nanoflakes epitaxially grown on defect MoS2 nanosheets for enhanced nitroarenes hydrogenation to anilines

Hydrogenation of nitroarenes to anilines under mild conditions is attractive from both theoretical and practical viewpoints. Here, high-performance catalyst with layered Pd nanoparticles epitaxially growing on ultrathin MoS2 nanosheets (Pd/MoS2) were prepared. It shows surprisingly high catalytic activity, selectivity and stability for hydrogenation of various nitroarenes to corresponding anilines; the turnover frequency is one or two magnitudes higher than conventional Pd-based catalysts. Surface sulfur vacancies are formed on MoS2 nanosheets with low formation energy barrier. These S vacancies provide efficient positions for adsorbing Pd atoms, which enables facile cleavage of N–O bond as result of strong interfacial electron interaction that decreases activation energy by 0.41 eV in comparison with conventional Pd catalysts. In situ spectroscopy and DFT calculation results reveal a dual-site mechanism, in which surface Pd sites adsorb and dissociate H2 into active H*, and then readily reacts with nearby activated nitroarene to form aniline on interfacial Pd-MoS2 sites.

Light-Driven Hydrogenation of Nitroarenes by Iron Catalysts Supported on TiO2

Light-Driven Hydrogenation of Nitroarenes by Iron Catalysts Supported on TiO2

Metal-facilitated, sustainable nitroarene hydrogenation under ambient conditions

Hydrogenation is a critical reaction in the chemical industry, yielding a range of important compounds such as fine chemicals, pharmachemicals and agrochemicals. However, conventional hydrogenation typically requires pressurized hydrogen, high temperatures and involves noble metal catalysts. We proposed a two-step hydrogenation process, utilizing water as the hydrogen source for the industrially important reduction of nitroarenes to anilines. A metal or reduced metal oxide, which can be obtained from solar thermal or electrochemical reduction, acts as the active site for nitrobenzene adsorption, H2O dissociation and in-situ hydrogen generation. Among the 15 metal and reduced metal oxides investigated, Zn and Sn emerged as highly efficient catalysts for the reduction of a broad range of organic nitro compounds under mild conditions, with H2 utilization efficiency 1–2 orders of magnitude above the state-of-the-art. The presented protocol provides extra dimensions for designing and optimizing conventional hydrogenation process with an alternative pathway. The reactive hydrogen atoms generated in-situ effectively overcome the barriers associated with hydrogen gas dissolution and its subsequent dissociation on the catalyst surface, thereby greatly enhancing the overall effectiveness for the hydrogenation reaction. This research potentially establishes a sustainable, generally applicable alternative to conventional hydrogenation methods, simultaneously presenting a viable solution for renewable energy storage.

Chiral crystalline organic salts as supports of Pd nanoparticles forming selective heterogeneous catalysts for hydrogenation of nitroarenes

A novel catalyst based on Pd nanoparticles encapsulated in a chiral crystalline organic salt matrix is prepared from tetrasodium tetrakis(4-sulfonatophenyl)methane and tetrakis[4-(S)-prolinamidophenyl]methane in water at room temperature under hydrogen atmosphere. The hydrogenation of p-nitrobenzaldehyde over this catalyst stalls at the stage of p-aminobenzyl alcohol, whereas Pd/C brings the reduction further to p-toluidine.

Unraveling discriminative-hydrogen-activation over Cu-based catalysts for boosting nitroarenes hydrogenation: Crystal effect and mechanism insight

Copper is a crucial element in the field of catalysis. However, Cu-based catalysts exhibit lower redox properties and surface energy under mild conditions, which limit their electron transfer capacities and catalytic performance. In this study, the relationship investigation between the hydrogenation behavior of Cu-based catalysts and crystal phases showed that spherical Cu2O exhibited enhanced capacity for hydrogen activation, excellent catalytic activity and outstanding reusability in the selective reduction of various nitroarenes. At even 25 °C and 1 atm, the complete reduction of 4-nitrophenol by NaBH4 was achieved in 2.5 min over Cu2O, achieving a reaction rate constant (k) of 20.15 × 10−3 s−1, which was 4.8 and 15.2 times that of CuO and Cu catalysts. Detailed experimental and theoretical calculations revealed that the Cu+ sites in the antifluorite crystal phase of Cu2O are conducive to the adsorption of active H species, while the unique d–s orbital recombination provides more electrons to improve its hydrogenation performance. The results of this study can aid in the development of copper-based materials as advanced catalysts, thereby improving fine chemical production and pollution treatment processes.

Metal‐2D Semiconductor Hybrid Nano‐Structure Catalyst: A New Frontier of Heterogeneous Catalysis

AbstractCatalytic hydrogenation of nitroarenes is a type of important reaction to get corresponding amines, the development of catalysts with outstanding catalytic performance is in urgent need. In this review, we summarize the breakthroughs in the development of supported metal catalysts in the past few decades, including the use of different metals and supports, improved metal utilization efficiency, adjustment of the structure, and the interaction. We focus on how to develop and innovate the structure of the catalyst, aiming at the contradiction between conversion and selectivity in selective hydrogenation of nitroarenes, from the perspective of the structure and the interaction to construct a kind of catalyst with low noble metal loading and high activity, stabilize the active components, and design and fabricate hybrid nanostructured catalysts with desired activity and selectivity. The development process and the catalytic performance of metal‐2D semiconductor hybrid nano‐structure catalyst are also discussed and provide a theoretical and practical basis for the precise design of supported metal catalysts.

Active cobalt nanoparticles confined in porous N-doped carbon shell for selective hydrogenation of nitroarenes

Selective hydrogenation is still challenging due to the trade-off between activity and selectivity of the catalyst. Hollow carbon shell confining cobalt nanoparticles is a competitive candidate catalyst, of which the structure and composition should be finely tailored for selective hydrogenation. In this work, Co in ZIF-67 is partially replaced by Zn and coated by polydopamine followed by pyrolysis to realize synergistic Zn regulation and N doping of shell-shaped carbon-cobalt catalyst. By changing Co/Zn ratio, the state of cobalt particles and the structure and composition of the N-doped carbon shell are effectively tuned. When Co/Zn ratio was 1:1, the as-prepared catalyst exhibited the best performance for selective nitro hydrogenation. H2 is dissociated on cobalt nanoparticles to generate active H radicals, which can be exchanged with H atoms of isopropanol as the solvent for facilitating hydrogenation. Selective adsorption of nitro group occurs on the N-doped carbon shell and the confined cobalt nanoparticles. The catalyst possesses good stability, which still maintained the original performance after 5 cycles.

Unveiling the origin of enhanced catalytic performance of CePO4/Pt for selective hydrogenation of nitroarenes

Supported catalysts are widely used in selective hydrogenation of nitroarenes, in which the choice of support has an important effect on the catalytic reaction rate and the selectivity of products. Herein, CePO4 as support to stabilize Pt nanoparticles for selective hydrogenation of nitroarenes is presented. The catalyst achieves a remarkable selectivity of aromatic amine production (>95 %) with a high turnover frequency (1476 h−1). Mechanistic studies reveals that the electronic structure of Pt is modulated by CePO4. In comparison to conventional CeO2/Pt catalyst, the Pt sites on CePO4 are negatively charged. Such configuration allows facile dissociation of H2 on Pt sites. Meanwhile, the potential-determining step (the formation of Ph-HNOH from Ph-HNO) on CePO4/Pt (0.73 eV) is a significantly lower than CeO2/Pt (1.15 eV), thereby favoring the pathway for aromatic amine production on Pt sites. Moreover, the CePO4 support has strong adsorption capacity of substrate, which plays a role as new active sites when adsorbed substrates are activated by active hydrogen species via hydrogen spillover. This work provides a new perspective into the development of selective nitroarenes conversion through the artful design of supported catalysts.

Precisely manipulating the local coordination of cobalt single-atom catalyst boosts selective hydrogenation of nitroarenes

Manipulating the local coordination environment holds immense potential in augmenting the catalytic performance of single-atom catalysts, which remains a great challenge. Through theoretical prediction, we find the catalytic properties of atomic Co centers towards selective hydrogenation of nitroarenes can be effectively manipulated by adjusting the coordinated number of P atoms, among which Co-N2P2 configuration stands out. Accordingly, a single-atom Co1-N/P-C catalyst featuring Co-N2P2 coordination was precisely fabricated through a sacrificial P-doped g-C3N4-template strategy. The optimal electronic structure of Co-N2P2 enables favorable chemical affinities toward nitroarene and H2, promoted heterolytic dissociation of H2, and accelerated reaction kinetics. Consequently, the Co1-N/P-C catalyst exhibits outstanding catalytic activity (overall TOF of 241.5 h−1), selectivity (>99%), and exceptional stability towards the hydrogenation of various functionalized nitroarenes, far surpassing other coordination configurations and most reported non-precious metal catalysts. This work deepens our understanding of the relationship between coordination structure and catalytic performance, offering boosted single-atom catalysts for selective hydrogenation of nitroarenes.

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods.

CeO2 nanorod based catalysts for the base-free synthesis of azoxy-aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (Ov ) and base sites are critical for their excellent catalytic properties. The Ov , i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α-Csp3 -H in ethanol to the nitro group coupling it to the redox reactions between Ce3+ and Ce4+ . At the same time, the base sites catalyze the condensation step to selectively produce azoxy-aromatics. The catalytic route opens a much improved way to use non-noble metal oxides without additives for the selective functional group reduction and coupling reactions.

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods

AbstractCeO2 nanorod based catalysts for the base‐free synthesis of azoxy‐aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (Ov) and base sites are critical for their excellent catalytic properties. The Ov, i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α−Csp3−H in ethanol to the nitro group coupling it to the redox reactions between Ce3+ and Ce4+. At the same time, the base sites catalyze the condensation step to selectively produce azoxy‐aromatics. The catalytic route opens a much improved way to use non‐noble metal oxides without additives for the selective functional group reduction and coupling reactions.

MoOx regulating Ni-based catalyst anchored on N-doped carbon microspheres for catalytic hydrogenation of nitroarenes

Reasonable modification of Ni-based catalysts is crucial for improving their catalytic activity in the nitroarenes hydrogenation but remaining a major challenge. Herein, a MoOx-promoted Ni-based bimetallic catalyst with fine Ni nanoparticles (only about 5.7 nm) anchored on N-doped carbon microspheres (NiMo1@NC-500) was prepared for the first time by a simple one-pot hydrothermal strategy and exhibits excellent catalytic activity for the probe reaction of nitrobenzene hydrogenation. The characterization and DFT calculations results elucidated that Ni and MoO2 sites promoted the activation and adsorption of H2; while the NiNx sites significantly enhanced the adsorption of the reaction substrate nitrobenzene. This synergistic adsorption mode endowed the catalyst with excellent nitrobenzene hydrogenation performance under mild conditions (80 °C, 1 MPa H2, 3 h). Moreover, the as-prepared catalyst exhibited robust stability for no less than 6 cycles and outstanding generality for the hydrogenation of other substituted nitroarenes, which provide a profound insight for the preparation of efficient and economical catalysts for the reduction of nitroarenes.

Nitrate and nitroarene hydrogenations catalyzed by alkaline-earth nickel phosphide clathrates.

The alkaline-earth-containing nickel phosphide clathrates AeNi2P4 (Ae = Ba, Sr) are investigated as catalysts for the reduction of nitrate or nitroarenes in aqueous or ethanolic solution, respectively. While AeNi2P4 clathrates are inactive in their bulk polycrystalline form, they become active in nitrate hydrogenation after size reduction by either grinding or ball milling. However, while the clathrate structure remains intact after manual grinding, ball milling is of limited use as it results in significant clathrate degradation. Ground AeNi2P4 catalysts are also active in nitroarene hydrogenation. Condensation products such as azoxy- and azo-benzenes form early (4 h) but anilines accumulate after long reaction times (24 h). Unexpectedly, BaNi2P4 partially devinylates nitrostyrene to nitrobenzene. Overall, BaNi2P4 is more active than SrNi2P4 in both nitrate and nitroarene hydrogenation. These results showcase the potential utility of clathrates in a growing number of catalytic transformations.

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor.

An electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines using a proton-exchange membrane (PEM) reactor was developed. Cyanoarenes were then reduced to the corresponding benzylamines at room temperature in the presence of ethyl phosphate. The reduction of nitroarenes proceeded at room temperature, and a variety of anilines were obtained. The quinoline reduction was efficiently promoted by adding a catalytic amount of p-toluenesulfonic acid (PTSA) or pyridinium p-toluenesulfonate (PPTS). Pyridine was also reduced to piperidine in the presence of PTSA.

Design of a gold nanoparticles site in an engineered lipase: an artificial metalloenzyme with enantioselective reductase-like activity.

The conjugation of gold complexes with proteins has proved to be interesting and effective in obtaining artificial metalloenzymes as catalysts with improved properties such as higher stability, activity and selectivity. However, the design and precise regulation of their structure as protein nanostructured forms level remains a challenge. Here, we have designed and constructed a gold nanoparticles-enzyme bioconjugate, by tailoring the in situ formation of gold nanoparticles (AuNPs) at two specific sites on the structure of an alkalophilic lipase from Geobacillus thermocatenulatus (GTL). For this purpose, two genetically modified variants of GTL were created by inserting a unique cysteine residue into the catalytic active site by replacing the active serine (GTL-114) and into the lid site (GTL-193). The enzyme, after a first protein-gold coordination, induced the in situ formation of AuNPs, generating a homogeneous artificial enzyme. The size and morphology of the nanoparticles in the AuNPs-enzyme conjugate have been controlled by specific pH conditions in synthesis and the specific protein region where they are formed. Reductase activity of all of them was confirmed in the hydrogenation of nitroarenes in aqueous media. The protein area seemed to be key for the AuNPs, with the best TOF values obtained for the bioconjugates with AuNPs in the lid site. Finally, the protein environment and the asymmetric properties of the AuNPs were tested in the reduction of acetophenone to 1-phenylethanol in aqueous medium at room temperature. A high reductive conversion and an enantiomeric excess of up to 39% towards (R)-1-phenylethanol was found using Au-Mt@GTL-114 pH 10 as a catalyst. Moderate enantioselectivity towards the opposite isomer was also observed using the Au-Mt@GTL-193 pH 10 conjugate.