Nitro Hydrogen Research Articles

Synergistic Nanoscale Mn3O4-CoO-Co Heterojunctions for Boosting the Selectivity in Hydrogenation of Nitrostyrenes and Nitroarenes.

Metal-metal oxide interface catalysts are in high demand for advanced catalytic applications due to their multi-component active sites, which facilitate synergistic cooperation where a single component alone cannot effectively promote the desired reaction. Demonstrated herein graphene oxide-supported nanoscale Mn3O4-CoO-Co as highly efficient catalysts for hydrogenation of nitro styrenes/nitro arenes to amino styrenes/arenes under mild reaction conditions (0.5 MPa and 100 °C in 1:1 THF/water). Charge relocalization at the Co-CoO-Mn3O4 heterojunction interfaces, primarily driven by Mn3O4, significantly improves reaction selectivity. Replacing Mn3O4 with MnO or using other supported bimetallic CoMnOx catalysts decreases selectivity, leading to the formation of a mixture of products. The catalyst demonstrated remarkable selectivity in converting nitro groups to amines, even in the presence of highly reactive functional groups such as C=C, O-C=O, C=O, C≡N, chalcones, and halides. It also exhibited high yields, multiple reusability, and a broad substrate scope. This study demonstrates how Mn3O4, in synergy with CoO-Co, fine-tunes selectivity, paving the way for the development of advanced metal-metal oxide interface catalysts to enhance both selectivity and efficiency in organic transformations.

Electrolytic Conversion of Nitro Compounds into Amines in a Membrane Reactor.

Aromatic and aliphatic amines are key intermediates in the synthesis of pharmaceuticals, dyes, and agrochemicals. These amines are often sourced from nitro compounds. The hydrogenation of nitro compounds into amines requires harsh reaction conditions (e.g., high pressures and high temperatures) or additives that are usually toxic. Here we demonstrate the electrochemically-driven hydrogenation of nitro compounds into amines in the hydrogenation compartment of a membrane reactor. The hydrogen is sourced from water in an adjacent electrolysis compartment separated by a hydrogen-permeable palladium membrane. Modifications of the palladium membrane with catalyst coatings enabled a wide range of commercially relevant nitro compounds to be hydrogenated into amines, without any additives, at ambient pressure and room temperature. This membrane reactor also enables nitro hydrogenation at high reagent concentrations with high functional group tolerance.

Yeast-derived N, P co-doped porous green carbon materials as metal-free catalysts for selective hydrogenation of chloronitrobenzene

The N, P co-doped porous carbon materials were synthesized via the in situ pyrolysis of yeast post-water treatment and exhibited superior nitro hydrogenation performance using molecular hydrogen and hydrazine hydrate as hydrogen sources.

Protein–metal ion networks coated carbon matrix as a precursor: to construct carbon-supported Mo-based catalysts with highly exposed active sites for hydrogenation of nitro compounds

Protein–metal ion networks coated carbon matrices were employed as a precursor for preparing carbon-supported Mo-based catalysts with highly exposed active sites for nitro hydrogenation.

Rationally engineering magadiite heavy metal adsorbent for p-nitrophenol hydrogenation reduction

The reutilization of spent heavy metal adsorbents as efficient heterogeneous catalysts is of great interests but remains a great challenge. In this work, cetyltrimethyl ammonium bromide intercalated magadiite (Mag) is facilely synthesized via cation exchange reaction, which possesses good uptake capacity towards metal ions and high structural stability. As a case study, these spent adsorbents loaded by Ag+, Zn2+, and Cu2+ species are recycled to construct nanohybrids MeOx-Mag and Me0-Mag (Me = Ag, Cu, and Zn) by calcining the exhausted solids under air and H2/Ar (5 vol% H2), respectively. The resultant imperfect pillared solids still inherit the interlayer space and nanosheet morphology from their Mag precursors, which is verified by abundant microscopic and spectroscopic characterizations. Importantly, Cu0 nanoparticle modified Mag (CuM) exhibits remarkable catalytic activity for a p-nitrophenol (p-NP) hydrogenation reduction. 100% p-NP (60 mL, 20 mg/L) can be converted into p-aminophenol (p-AP) within 30 min when 2 mg CuM is used with the assistance of 10 mg NaBH4. Discrete Cu0 nanoparticles promote the generation of active H⁎ and thus the heterogeneous catalysis for p-AP products. The catalytic performance with important parameters (Cu0 loading amount, p-NP initial concentration, NaBH4 addition dosage, etc.) is discussed extensively to understand how to prefer reaction conditions for optimum nitro hydrogenation performance. The present study provides a rational design of spent Mag-based adsorbents for advanced environmental and catalysis applications via exploring the potential value of solids post-use.

Inserting Single-Atom Zn by Tannic Acid Confinement To Regulate the Selectivity of Pd Nanocatalysts for Hydrogenation Reactions.

Precisely controlling the selectivity of nanocatalysts has always been a hot topic in heterogeneous catalysis but remains difficult owing to their complex and inhomogeneous catalytic sites. Herein, an effective strategy to regulate the chemoselectivity of Pd nanocatalysts for selective hydrogenation reactions by inserting single-atom Zn into Pd nanoparticles is reported. Taking advantage of the tannic acid coating-confinement strategy, small-sized Pd nanoparticles with inserted single-atom Zn are obtained on the O-doped carbon-coated alumina. Compared with the pure Pd nanocatalyst, the Pd nanocatalyst with single-atom Zn insertion exhibits prominent selectivity for the hydrogenation of p-iodonitrobenzene to afford the hydrodeiodination product instead of nitro hydrogenation ones. Further computational studies reveal that the single-atom Zn on Pd nanoparticles strengthens the adsorption of the nitro group to avoid its reduction and increases the d-band center of Pd atoms to facilitate the reduction of the iodo group, which leads to enhanced selectivity. This work provides new guidelines to tune the selectivity of nanocatalysts with guest single-atom sites.

Trash to treasure: Converting red mud into efficient catalysts for the hydrogenation of p-nitrobenzene compounds

Herein, we demonstrate that the red mud can be employed as a valuable resource for fabrication of efficient catalysts for the hydrogenation of p-nitrobenzene compounds. The pyrolysis of reed effectively promotes the reduction of hematite (Fe2O3) of RM into magnetite (Fe3O4). The structural characterizations indicate that the magnetite nanoparticles are distributed on the surfaces of biomass carbon with strong interaction. Moreover, the as-obtained catalysts contain vast basic groups inherited from red mud, which facilitate the adsorption and ionization of p-nitrobenzene compounds. At the same time, the magnetic Fe3O4 components catalyze the hydrolysis of NaBH4 to produce active hydrogen species, resulting in the hydrogenation of nitro to amino group under ambient conditions. Therefore, this work may provide a new strategy of trash to treasure by the rational design and development of red mud based functional materials.

Breaking binary competitive adsorption in the domino synthesis of pyrroles from furan alcohols and nitroarenes over metal phosphide

Herein, an efficient domino synthesis for N-aryl pyrroles and tetrahydropyrroles from biomass-derived furan alcohols (i.e., 5-methyl furfuryl alcohol, and 2,5-bis(hydroxymethyl)furan) and nitrobenzenes was reported for the first time over metal phosphides. Dual active sites, including metal sites for nitro hydrogenation, acid sites for furan alcohol ring-opening determine the catalytic performance. Different from traditional tandem catalysts of Pd/C and HZSM-5 or Amberlyst-15 that suffer from binary competitive adsorption of furan and nitro groups on metal sites, as well as hydroxyl and hydrogenated amino groups on the acidic sites, metal phosphides show unexpected cooperative catalytic properties with the oriented synthesis of pyrroles over NiCoP and tetrahydropyrroles over Ni2P. Furthermore, the catalyst displays outstanding stability and recycling performance after 4 runs. This work demonstrates an effective strategy for governing reaction routes by selective activation and shows the powerful synergistic effect of hydrogenation and acid catalysis.

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Cleaner production of disperse florescent dyes in supercritical CO2 and their applications in dyeing polyester fabric

Supercritical carbon dioxide (scCO2) is commonly used as an excellent solvent in chemical reactions and dyeing fields because of its advantages. In this work, three coumarin and 1,8-naphthalimide fluorescent dyes (DAMC, NP-NH, and NP-dimethyl) were successfully constructed on the basis of the Au/titanium dioxide (Au/TiO2) catalytic reduction of nitro in scCO2 instead of SnCl2/hydrochloric acid solution, and their structures were confirmed correctly by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The cleaner synthesis and dyeing polyester fabrics of coumarin derivative (DAMC) in the presence or absence of N-methyl-pyrrolidone (NMP) were first studied by employing stepwise and synchronous methods. All results for DAMC indicated that the synchronous synthesis and dyeing method is more beneficial. Here, the synchronous synthesis and dyeing polyester fabrics of 1,8-naphthalimide derivatives (NP–NH and NP-dimethyl) in scCO2 were also investigated. Through the comprehensive analysis of color strength (K/S) value and fixation rate, the optimal temperatures and pressures of synthesis and dyeing for NP-NH and NP-dimethyl were obtained in the absence or presence of NMP. The dyed fabrics with NP-NH and NP-dimethyl exhibited yellow or yellowish-brown in daylight and bright fluorescent yellowish-green in ultraviolet light. All results showed that the clean production of fluorescent dyes (DAMC, NP-NH, and NP-dimethyl) can be realized by the hydrogenation of nitro with efficient Au/TiO2 catalyst in scCO2, meanwhile, the synchronous synthesis and dyeing method was proposed for the synthesized dyes. The realization of synchronous synthesis and dyeing fabrics for fluorescent dyes in scCO2 is an effective way to prevent environment pollution brought by the processes of synthesis and dyeing. Thus, the constructing and dyeing strategy of fluorescent dyes will be beneficial to the sustainable development of environment.

Efficient visible light initiated one-pot syntheses of secondary amines from nitro aromatics and benzyl alcohols over Pd@NH2-UiO-66(Zr)

Pd@NH2-UiO-66(Zr), with small-sized Pd nanoparticles encapsulated inside the cavities of NH2-UiO-66(Zr), was obtained via a double-solvent impregnation followed by a photoreduction process, which shows superior activity for the visible light initiated syntheses of secondary amines from nitro compounds and alcohols, via a sequential photocatalytic hydrogenation of nitro compounds/dehydrogenation of alcohols, condensation of amines and aldehydes to imines, and the hydrogenation of imines. Simultaneous consumption of photogenerated electrons/holes in the photocatalytic hydrogenation of nitro compounds to amines and dehydrogenation of alcohols to aldehydes promotes the whole reaction. Due to the confinement effect of the cavity and the small-sized Pd nanoparticles, Pd@NH2-UiO-66(Zr) shows significantly superior performance as compared with Pd/NH2-UiO-66(Zr), in which larger Pd nanoparticles are deposited on the surface. This study provides an efficient and green strategy for the production of secondary amines and highlights the great potential of using M/MOFs nanocomposites as multifunctional catalysts for light induced one-pot tandem reactions.

Highly Dispersed CoFe Catalyst for Selective Hydrogenation of Biomass‐Derived Furfural to Furfuryl Alcohol

Biorefinery to fabricate biofuels, chemicals, and materials has attracted much attention. Herein, a highly dispersed non‐noble CoFe immobilized on nitrogen‐doped carbon catalyst is prepared via a template sacrificial method. Owing to the synergetic effect of Co and Fe, the high dispersity of CoFe nanoparticles and large specific surface area, the optimized Co9‐Fe1‐NC catalyst exhibits high activity for the selective hydrogenation of furfural (FAL) to furfuryl alcohol (FOL). Hundred percentage conversion of FAL and 99% selectivity of FOL are obtained at 120 °C with 1 MPa H2 for 4 h, which is superior to most of the reported nonprecious catalysts. Moreover, the Co9‐Fe1‐NC catalyst can also catalyze the hydrogenation of nitro and carbonyl compounds efficiently. The mechanism of hydrogenation of FAL is revealed by density functional theory calculations. This work provides a promising synthetic strategy for the rational structural design of efficient selective hydrogenation catalysts.

Synthesis, Structure, and Catalytic Hydrogenation Activity of [NO]-Chelate Half-Sandwich Iridium Complexes with Schiff Base Ligands.

A series of N,O-coordinate iridium(III) complexes with a half-sandwich motif bearing Schiff base ligands for catalytic hydrogenation of nitro and carbonyl substrates have been synthesized. All iridium complexes showed efficient catalytic activity for the hydrogenation of ketones, aldehydes, and nitro-containing compounds using clean H2 as reducing reagent. The iridium catalyst displayed the highest TON values of 960 and 950 in the hydrogenation of carbonyl and nitro substrates, respectively. Various types of substrates with different substituted groups afforded corresponding products in excellent yields. All N,O-coordinate iridium(III) complexes 1-4 were well characterized by IR, NMR, HRMS, and elemental analysis. The molecular structure of complex 1 was further characterized by single-crystal X-ray determination.

Synthesis of new tetrahydropyridopyrazine derivatives via continuous flow chemistry approach and their spectroscopic characterizations

AbstractWe report here the synthesis of different substituted tetrahydropyridopyrazine derivatives. This approach of synthesis has been designed in a way that in first simple chloro‐amine coupling as an alternative of Buchwald coupling followed by heterogeneous hydrogenation of nitro to give amine and further cyclization of this amine with carboxylic acid was accomplished in a single process with the help of continuous flow hydrogenation reactor. This processing was a generation of hydrogen (in situ) by electrolysis of water molecule and using a pre‐packed cartridge of a palladium catalyst. In a further step, LAH was used to reduce lactam to a yielding product as tetrahydropyridopyrazine (TPP) scaffold. Final adducts were obtained using substituted benzoyl and sulfonyl derivatives.

Aluminum Metal–Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis

The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal–organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon–oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.

Hydrogenation of Substituted Benzenes Containing Nitro and Azo Groups over Skeletal Nickel in Aqueous Solutions of 2-Propanol

An analysis is made of the kinetic characteristics of the hydrogenation of 4-nitro- and 2-nitro-2'-hydroxy-5'-methylazobenzenes, 4-nitroaniline and 4-aminoazobenzene over skeletal nickel in neutral azeotropic 2-propanol–water mixture and in the same solvent in the presence of acetic acid or sodium hydroxide. It is found that the selectivity of the hydrogenation of these isomers to the intermediate products depends on the composition and nature of the solvent, and is determined by the rate of reactive group conversion. Compared to the process in the presence of sodium hydroxide, which suppresses the route leading to the predominant hydrogenation of the nitro group, the contribution from the transformation of azo group is considerably greater in the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of acetic acid. Adding a base to the solvent during the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene accelerates the rate of nitro group conversion and the intramolecular cyclization of the intermediate compound, increasing the selectivity towards the products containing the benzotriazole cycle (particularly 2-(2-hydroxy-5-methylphenyl)benzotriazole-N-oxide). The almost linear correlation between the selectivity of the catalytic hydrogenation of isomers of nitro-2'-hydroxy-5'-methylazobenzene and the kinetic characteristics of the hydrogenation of nitro and azo groups in compounds containing a single reactive substituent at different values of medium’s pH is estimated.

Effects of Preparation Parameters of NiAl Oxide-Supported Au Catalysts on Nitro Compounds Chemoselective Hydrogenation.

Effects of preparation parameters of NiAl oxide-supported Au nanocatalysts on their performance in the chemoselective hydrogenation of nitro compounds were investigated. The deposition–precipitation method, low Au loading, and low Ni/Al molar ratio of the support contributed to the generation of small-sized Au nanoparticles. High catalytic properties were related to the small sizes of Au particles and appropriate basicity of supports. Accordingly, the 0.43% Au/NiAlO-2-500 (the Ni/Al molar ratio of the support = 2) showed high activity and excellent selectivity for nitro hydrogenation. It also showed good versatility for other nitro compounds and good recyclability. Interestingly, for the first time, this Au catalyst switched its selectivity to vinyl hydrogenation by mere regulation of the composition of the support (the Ni/Al molar ratio of the support = 4). The observed shift in selectivity was ascribed to the different adsorption behaviors of the nitro and vinyl group on Au nanocatalysts. It provides a novel and facile strategy to construct Au nanocatalysts with high activity and switchable selectivity for hydrogenation of nitro compounds by the fine tuning of preparation parameters.

Moderate Activity from Trace Palladium Alloyed with Copper for the Chemoselective Hydrogenation of –CN and –NO2 with HCOOH

AbstractThe chemoselective hydrogenation to afford functionalized amines is a challenging task in the field of applied catalysis. In this work, we constructed a versatile catalytic system for the nondestructive hydrogenation of nitro and cyano group to afford the functionalized aromatic and primary amines under mild conditions. The dilemma of effects on other sensitive functional groups in the hydrogenation is solved by the precisely controlled activity from the trace palladium alloying with copper in our catalyst. The TOF achieved 5376 h−1 and 322581 h−1 for Pd when the functionalized nitriles and nitroarenes were used as substrate respectively. In a word, the good compatibility and recyclability, the mild operation conditions, extremely low consumption of noble metal, ppm level Pd, and economically available hydrogen donor, HCOOH, highlight the contribution of this work.

Production of bacterial nanocellulose (BNC) and its application as a solid support in transition metal catalysed cross-coupling reactions.

Bacterial nanocellulose (BNC) emerged as an attractive advanced biomaterial that provides desirable properties such as high strength, lightweight, tailorable surface chemistry, hydrophilicity, and biodegradability. BNC was successfully obtained from a wide range of carbon sources including sugars derived from grass biomass using Komagataeibacter medellinensis ID13488 strain with yields up to 6 g L-1 in static fermentation. Produced BNC was utilized in straightforward catalyst preparation as a solid support for two different transition metals, palladium and copper with metal loading of 20 and 3 wt%, respectively. Sustainable catalysts were applied in the synthesis of valuable fine chemicals, such as biphenyl-4-amine and 4'-fluorobiphenyl-4-amine, used in drug discovery, perfumes and dye industries with excellent product yields of up to 99%. Pd/BNC catalyst was reused 4 times and applied in two consecutive reactions, Suzuki-Miyaura cross-coupling reaction followed by hydrogenation of nitro to amino group while Cu/BNC catalyst was examined in Chan-Lam coupling reaction. Overall, the environmentally benign process of obtaining nanocellulose from biomass, followed by its utilisation as a solid support in metal-catalysed reactions and its recovery has been described. These findings reveal that BNC is a good support material, and it can be used as a support for different catalytic systems.

Reversible Control of Chemoselectivity in Au38(SR)24 Nanocluster-Catalyzed Transfer Hydrogenation of Nitrobenzaldehyde Derivatives.

Chemoselective hydrogenation of nitrobenzaldehyde derivatives is one of the important catalytic processes being studied in hydrogenation catalysis. In this work, we report for the first time the catalytic reaction over atomically precise gold nanocluster catalysts (Au25, Au38, Au52, and Au144) using potassium formate as the hydrogen source. A complete selectivity for hydrogenation of the aldehyde group, instead of the nitro group, is obtained. A distinct dependence on the size of nanocluster catalysts is also observed, in which the Au38(SCH2CH2Ph)24 gives rise to the highest catalytic activity. The catalyst also shows good versatility and recyclability. Interestingly, the ligand-off nanocluster changes its catalytic selectivity to the nitro hydrogenation, which is in contrast with the ligand-on catalyst. In addition, the selectivity can be restored by treating the ligand-off nanocluster catalyst with thiol. This reversible control of chemoselectivity is remarkable and may stimulate future work on the exploitation of such nanoclusters for hydrogenation catalysis with control over selectivity.