Reduction Of Nitroaromatics Research Articles

Copper Nanoparticles-Decorated Carbon Nanoflakes as a Catalyst for Nitroaromatic Reduction

Copper Nanoparticles-Decorated Carbon Nanoflakes as a Catalyst for Nitroaromatic Reduction

Porous Pd-Loaded IRMOF-9 as Highly Efficient Recyclable Material Towards the Reduction of Nitroaromatics in Aqueous Media.

Nitroaromatic compounds (NACs) cause severe hazardous impacts on human health as well as on the environment. Therefore, there is dire need to develop a robust material to reduce the toxicity of these organic pollutants. In this regard, our group developed a series of porous MOF materials viz., Pdx@IRMOF-9 (x=2 %, 5 % and 10 %) by loading different concentration of Pd(II) on IRMOF-9 and explored them towards reduction of different nitroaromatic compounds. Pd10%@IRMOF-9showed ~30 % greater efficiency for the reduction of 4-NP as compared to Pd2%@IRMOF-9. Pd10%@IRMOF-9showed excellent reduction ability (>85 %) towards 4-NP, 2-NP, 2-NA, 3-NA and 2,4-DNPH. The kinetic studies indicates that the reduction follows the pseudo-first-order kinetics. Moreover, the rate constant value for reduction of 3-NA was ~9 times higher than that of 2-NP. Based on the kinetic parameters, the t1/2 values for all the nitroaromatics have been calculated. The kinetic parameters, Km and Vmax have been calculated from double reciprocal Lineweaver-Burk plot and found to be 65.984 μM and 116×10-6 Mmin-1 respectively. Pd10%@IRMOF-9showed excellent recyclability towards the reduction of 4-NP for few consecutive cycles without any remarkable loss in its activity. Thus, highly efficient, porous and robust material for the reduction of nitroaromatic compounds in aqueous media have been demonstrated.

Prodrug activation by 4,4’-bipyridine-mediated aromatic nitro reduction

Unleashing prodrugs through nitro-reduction is a promising strategy in cancer treatment. In this study, we present a unique bioorthogonal reaction for aromatic nitro reduction, mediated by 4,4‘-bipyridine. The reaction is a rare example of organocatalyst-mediated bioorthogonal reaction. This bioorthogonal reaction demonstrates broad substrate scope and proceeds at low micromolar concentrations under biocompatible conditions. Our mechanistic study reveals that water is essential for the reaction to proceed at biorelevant substrate concentrations. We illustrate the utility of our reaction for controlled prodrug activation in mammalian cells, bacteria, and mouse models. Furthermore, a nitro-reduction-annulation cascade is developed for the synthesis of indole derivatives in living cells.

Anchoring of Ni(II)-Schiff base complex in surface modified SBA-15: A reusable and efficient heterogeneous catalyst for nitroaromatic reduction

A newly designed Ni(II) dimeric Schiff-base complex [NiL] has been synthesized with our earlier reported ligand. Here, the aim is to study the catalytic activity of [NiL] towards reduction of nitroarenes by using NaBH4.Various physicochemical techniques were employed to characterize the complex, [NiL] including single-crystal X-ray diffraction. The homogeneous complex [NiL] exhibited superior catalytic efficiency, prompting its selection for the development of a recyclable heterogeneous catalyst. This was done by immobilizing it over a surface-modified SBA-15 functionalized with 3-aminopropyl group. The resulting SBA-15@APTES@NiL (SBNi) catalyst was thoroughly characterised by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Powder X-ray Diffraction and N2 adsorption analysis, which suggested successful immobilization of the nickel complex on the solid support. This heterogeneous catalyst demonstrated stability in both organic and aqueous medium, facilitating the reduction of nitroarenes in presence of NaBH4. A pseudo first order reaction was observed with a rate constant value 0.09617 min-1 and correlation parameter (R2) 0.9735 for the nitrophenol reduction in presence of high concentration of NaBH4. Additionally, the surface-modified catalyst allowed for easy separation through filtration. The catalyst retained recyclability up to five cycles without any significant change in catalytic activity.

Preparation of PdNi bimetallic loaded amino modified porous carbon material catalyst based on chitosan and its applications

The utilization efficiency of palladium-based catalysts has sharply increased in many catalytic reactions. However, numerous studies have shown that preparing alloys of palladium with other metals has superior catalytic activity than pure palladium. Additionally, hierarchical porous carbon has gradually developed into an excellent carrier for loading bimetallic nanoparticles. In this study, we firstly pyrolyzed chitosan, sodium bicarbonate and nickel nitrate to create highly dispersed porous carbon materials doped with Ni NPs. The carbon materials were then grafted with silane coupling agent (APTMS) to afford them with amino groups on the surface. Taking advantage of the fact that Pd2+ can react with Ni in spontaneous reduction reaction, Pd was deposited on the surface of Ni to produce PdNi bimetallic-loaded carbon catalysts containing amino groups. The resulting catalysts were examined by a series of characterizations and were found to have a hierarchically porous structure and large specific surface area, which increased the number of active sites of the catalysts. In comparison to other Pd catalysts, the PdNi/HPCS-NH2 catalysts displayed remarkable activity for Suzuki coupling reaction and hydro reduction of nitroaromatics, which exhibited a high turnover frequency value (TOF) of 37,857 h−1 and 680.9 h−1, respectively. These were mainly due to the high dispersion of the PdNi NPs and the superior structure of the carriers. Moreover, the catalysts did not experience a significant decline in activity after ten cycles. All in all, this investigation has created a new approach for the fabrication of novel carriers for Pd catalysts, which is in line with the concept of green chemistry and recyclable.

Axial coordination engineering of atomic Co–N4 sites for exceptional aromatic nitroreduction

Optimizing the local environment of metal active centers bonded by nitrogen ligands (M−N4) through additional axial coordination provides a promising approach to enhance the reaction kinetics of heterogeneous catalysis. However, achieving precise targeting and construction of efficient active sites remains a major challenge. In this study, under the guidance of density functional theory (DFT) calculations, we precisely position and engineer atomic Co–N4 active sites with axial O coordination on porous carbon nanosheets (Co1/NOC) for boosted aromatic nitroreduction through a novel template-anchoring strategy. The resulting Co1/NOC catalyst exhibited unprecedented catalytic activities towards a series of functionalized nitroaromatics with a record overall turnover frequency (TOF) of 38022 h−1 under mild reaction conditions, 7.6- and 38 times higher than that of Co–N4 sites (Co1/NC) and commercial Pd/C catalysts, respectively, standing ahead of the reported catalysts. Targeted DFT calculations reveal that axial oxygen coordination efficiently promotes the electronic delocalization of the Co center, which dramatically facilitates the formation and utilization of reactive H* species, enhances the selective adsorption of nitroaromatics, and accelerates the conversion of aromatic nitroreduction, eventually attaining exceptional catalytic performance. This work offers a new avenue for precisely tailoring the coordination environment of single-atom catalysts to achieve advanced catalytic performance in chemical transformations.

Catalytic Nano-Gold Immobilized on the Inner Surfaces of Halloysite Nanotubes for Selective Reduction of Nitroaromatics

Catalytic Nano-Gold Immobilized on the Inner Surfaces of Halloysite Nanotubes for Selective Reduction of Nitroaromatics

Novel highly utilized PdNi bimetallic-loaded N-doped carbon catalysts prepared from MOF for Suzuki coupling reaction and hydro reduction of nitroaromatics

The usage of palladium-based catalysts in numerous chemical reactions has been increased significantly; in particular, the synthesis of heterogeneous catalysts by attaching palladium atoms to carriers has expanded rapidly. Therefore, the selection of nitrogen-doped carbon materials for carriers has become a popular research subject. In this study, Ni-Ni PMOF was first created, then Ni nanoparticles (NPs) modified nitrogen-doped mesoporous carbon materials were synthesized through pyrolysis. Subsequently, Pd atoms were successfully deposited onto the surface of Ni NPs as Pd2+ is capable of being reduced by metal Ni. The structure of the prepared carriers was verified by FT-IR, XRD, SEM, TEM, XPS and other characterizations, and was found to have a fluffy and porous structure that increases the number of active sites of PdNi NPs. This material was found to be effective in catalyzing the Suzuki coupling reaction (TOF = 1019 h) and the reduction reaction of p-nitrophenol (Kapp = 4.34 × 10−2 s−1), and its catalytic activity remained stable even after 10 uses, showing good recoverability and recyclability. This study thus provides a novel approach for the preparation of N-doped porous carbon materials, which can enable green chemistry by making efficient and full use of precious metals.

Green sustainable synthesis of Ag doped SnO2 decorated reduced graphene oxide hierarchical nanohybrid material: An excellent mesoporous catalyst for efficient reduction of nitroaromatics

A foliose lichen species, Lobaria retigera mediated environmentally sustainable, economically viable green synthesis procedure to access Ag doped SnO2 (Ag@SnO2) and hierarchical Ag doped SnO2 decorated reduced graphene oxide (rGO-Ag@SnO2) nanohybrid material is reported. Carbohydrate, a primary metabolite present in the aqueous lichen extract is presumed to be responsible for the reduction and stabilization of the nanoparticles. The nanoparticles were mostly spherical with < 5 nm sizes. The co-existence of Ag and SnO2 is validated by XRD and EDS studies. The XPS spectra revealed the +IV oxidation state of Sn. The hybrid material can efficiently catalyse reduction of toxic aromatic nitro compounds which meet most of the rigorous demands of sustainable development goals and clean technology. The reduction efficiencies of 81–91% in a time span of 2–18 minutes were achieved due to the unique hierarchic porous architecture of the ternary hybrid material. The reduction of nitroaromatics to amino-compounds were confirmed by UV–visible spectroscopy and LC-MS study. The recyclability of the catalysts were confirmed by performing repeated reduction reactions with virtually no loss of its catalytic features. BET study of the hybrid materials revealed a type IV with H3 hysteresis loop indicating a high mesoporous nature with significant extended surface area. The dispersed Ag doped rutile-SnO2 over rGO sheet could be clearly discerned from TEM and SEM micrographs. Elemental mapping distinctly revealed the homogeneous distribution of the constituent elements in the hybrid materials

Enhancing nitroaromatics reduction through synergistic participation of Ni NPs and nickel ferrite/C nanocomposite: A path towards greener industrial viability

Ni/Fe-citrate gel was reduced in an H2/Ar, forming Ni NPs decorated NiFe2O4-C for eco-friendly nitroaromatics reduction. In-depth characterization of the catalyst highlighted the synergistic interaction between Ni NPs and NiFe2O4 (Ni/NiFe2O4-C), achieving ∼ 99 % conversion of nitroaromatics into amines at 70 °C and 0.5 MPa H2 in water. The cooperative effects of Ni NPs, NiFe2O4, and carbon were instrumental in enhancing the adsorption of hydrogen and nitroaromatics, and the kinetic study showed effectively reducing the activation barrier for the reduction. The HR-TEM, XPS, and H2-TPR provided valuable insights into the formation of Ni NPs and the NiFe2O4 framework, emphasizing their synergistic relationship. Raman spectroscopy and TGA analysis confirmed the formation of carbon. Remarkably, the highly active Ni/NiFe2O4-C catalyst recycled for five cycles without losing activity. p-Aminophenol on 7 g will receive significant attention, emphasizing the substantial promise of this sustainable transition metal-based catalyst for the eco-friendly hydrogenation of nitroaromatics.

Green preparation of fiberboard waste derived N–doped carbon catalysts with tailored properties for efficient hydrogenation reduction of nitroaromatics

Biomass–derived carbon materials doped with diverse heteroatoms have demonstrated huge potentials for environment and energy applications, thanks to the availability, preferable porous and channel structures, and excellent conductivity and stability. In this work, fiberboard waste containing resin–based adhesive was selected for the green fabrication of N–doped carbon catalysts without using extra N–sources. A facile two–step calcination strategy with sequential carbonization and activation was proposed for generation and exposure of indispensable active sites, realizing the controllable regulation of textural and morphological characteristics. The resulting N–doped fiberboard derived carbon (NFC) samples possessed unique hierarchically porous structures with a significantly enlarged surface area, plentiful activity–dependent N species (e.g., graphitic N and pyridinic N), as well as suitable graphitization degree and surface hydrophilicity. As a result, a favorable adsorption procedure and an enhanced accessibility of active sites synergistically boosted the catalytic performance towards hydrogenation reduction of nitroaromatics. Taking the NFC–hh sample as paradigm, an excellent performance was demonstrated for 4–nitrophenol (4–NP) reduction, achieving a high apparent rate constant of 0.40 min−1 and an impressive turnover frequency of ∼0.20 mmol g−1 min−1. Besides, the continuous–flowing catalytic test exhibited an excellent conversion efficiency > 99.50% with a long–term stability over 100 h, showing an attractive prospect for industrial application. This work presents a new approach for high value–added utilization of biomass waste, and provides a low–cost and high–active catalyst for environmental remediation.

Carbon derived from orange peel waste for preparation of benign bimetallic catalyst in organic reactions

In this work, a convenient approach has been applied to discover the potential valorization of biomass waste such as orange peel in which PdCu-based nanostructured systems were synthesized via a one-step in-situ dry-milling approach to obtain the benign bimetallic catalysts with different palladium(Pd) and Copper(Cu) loadings on the orange peel support (Pd1%Cu1%, Pd0.3%Cu0.7%, Pd0.5%Cu0.5%, Pd0.5%Cu1%). Catalytic applications of these new composites were investigated in the Sonogashira-Hagihara coupling reaction as well as the Sonogashira–click reaction sequence to the preparation of substituted 4-aryl-1,2,3-triazoles and reduction of nitroaromatics under mild reaction conditions. Catalytic tests with the four activated carbons catalysts showed that the C@Pd1%Cu1% catalyst was the most active in the Sonogashira-Hagihara coupling reaction compared to the other catalysts. Also, the C@Pd0.5%Cu0.5% catalyst showed the highest catalytic activity in the reduction of 1-chloro-4-nitrobenzene and 4-nitrophenol in comparison with other prepared carbon catalysts.

Deciphering Nitroaromatics Reduction: Theoretical Insights into Dioxomolybdenum Catalysis with Biomass‐Derived Pinacol

AbstractDensity Functional Theory is used to unravel the mechanism of the nitrobenzene to aniline reduction, catalyzed by dioxomolybdenum (VI) dichloride. The use of pinacol as an oxoaccepting reagent and the production of only acetone and water as byproducts, signals a novel and environmentally friendly way to add value to the oxygen‐rich biomass‐derived polyols. The reaction proceeds through three consecutive cycles, each one responsible for one of the three reductive steps needed to yield aniline from nitrobenzene, with nitrosobenzene and hydroxylamine as intermediates. Each cycle regenerates the catalyst and releases one water and two acetone molecules. The mechanism involves singlet/triplet state crossings, a crucial feature in polyoxomolibdate catalyzed processes. The role of the Mo‐coordinated water as the provider of the mysterious protons needed to reduce the nitro group, was revealed. The disclosure of this challenging mechanism and its rate limiting step can contribute to the design of more effective Mo(VI) catalysts.

Surface Deposition of Magnesium Ferrite-Based Supports with Bimetallic Gold/Silver Nanoparticles for the Catalytic Reduction of Nitroaromatics.

Surface deposition of magnesium ferrite nanoparticles (MgFe2O4 NPs) with bimetallic gold/silver (Au/Ag) nanoparticles was conducted using the seed-mediated growth method to obtain magnetic-metallic composite catalysts for use in the catalytic reduction of nitroaromatics. Two types of amine-functionalized MgFe2O4 and MgFe2O4@SiO2 NPs were used as magnetic supports for the surface deposition process. The combination of several characterization analyses (i.e., XRD, XPS, TEM, SEM, EDS, and VSM) confirmed the successful syntheses of the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs. The catalytic reduction of 4-nitrophenol using sodium borohydride as a reducing agent revealed that the reaction was completed within 2 min by using MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs as catalysts. The appearance rate constant of the MgFe2O4/Au/Ag NPs was slightly higher than that of the MgFe2O4@SiO2/Au/Ag NPs. In terms of reusability, high conversion (>80%) of the reduction of 4-nitrophenol was still obtained after 7 and 10 consecutive cycles for the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag catalysts, respectively. Interestingly, these two catalysts exhibited the highly catalytic conversion of the chosen nitroaromatic derivatives (i.e., 4-nitrobenzaldehyde and 4-nitroaniline). On the whole, the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs could be utilized as suitable and sustainable catalysts for the catalytic reduction of nitroaromatics due to several desirable features (i.e., high activity, facile and rapid separation by a magnet, and good reusability).

Fast and efficient reduction of nitroaromatic compounds with copper oxides supported nitrogen-sulfur Co-doped porous carbon material derived metal-organic framework

The expansion of heteroatom-doped carbons with metal-organic frameworks (MOFs) as precursors under heat treatment has attracted extensive attention for the betterment of the catalytic attributes of carbon-based catalysts. After simply pyrolyzing metal-organic framework (MOF) mixed with thiourea (CH4N2S) particles, N and S-doped porous carbon substrates with favorable structural and compositional properties are obtained. The as-synthesized material, which is named CuxO@CNS-400 acts as a heterogeneous catalyst in the reduction reaction of nitro-aromatic compounds, which has superior performance with high activity. The morphology, structure, and physicochemical properties of CuxO@NSC-400 were successfully synthesized and characterized using XRD, TEM, TGA, FE-SEM, EDX, FT-IR, and Raman. In particular, CuxO@CNS-400, obtained by pyrolysis at 400 °C, demonstrates excellent catalytic efficiency of 98 % and high catalytic cycling stability for rapid and highly efficient nitro aromatics reduction.

Influence of TiO2 phases and functional groups on photocatalytic reduction of nitroaromatics

Photocatalytic organic transformations have emerged as environmentally sustainable alternatives to traditional synthesis routes. This study delves into the intricacies of photocatalytic reduction of nitroaromatics using bare TiO2 materials, shedding light on critical factors that govern this green and sustainable transformation. Our systems reveal very promising conversion and selectivity levels, consistently exceeding 90% across 13 diverse nitroaromatic substrates. The position and nature of functionalities (e.g., electron withdrawing/donating groups) within the nitroaromatic molecule, as well as the crystal phase of TiO2 (anatase/rutile), emerged as crucial determinants of reaction efficiency. Furthermore, the pivotal role of methanol in this system is highlighted, not only facilitating efficient hole scavenging and byproduct prevention but also multiplying reduction efficiency. This work emphasizes the significance of careful solvent selection, crystal phase optimization, and the role of functional groups as the so-called external factors in optimizing photocatalytic reactions for sustainable and environmentally friendly synthesis.

Liquid-Liquid interfacial approach for rapid synthesis of Well-Crystalline Two-Dimensional Metal-Organic frameworks for nitro reduction

Two-dimensional metal–organic frameworks (2D MOFs) have garnered significant attention due to their exceptional properties across diverse research domains, including catalysis, biomedicine, gas adsorption, separation, energy storage, and sensing. Despite these promising attributes, the facile and large-scale synthesis of 2D MOFs with high crystallinity remains a formidable challenge. In this study, we propose a novel approach based on a modified liquid–liquid interfacial method for the rapid synthesis of well-crystalline 2D MOFs. By vigorously mixing water, a hydrophobic solvent, and an emulsifier, we generate micrometer-sized droplets that create substantial curved two-phase interfaces. This method is compatible with various ligands and metal ions, enabling the rapid formation of 2D MOFs at these curved interfaces under additional pressure. The subsequent separation of oil and water phases via centrifugal force promotes moderate π-π stacking within the 2D MOF, thereby stabilizing the lamellar structure and enriching the material at the two-phase interface. Remarkably, the entire synthesis process requires a mere 3 min, yielding grams of product in a single run. Furthermore, solvent reuse does not compromise the quality of the resulting 2D MOFs. As a practical application, we synthesized phthalocyanine (Pc)-based structures using this method for the catalytic reduction of nitroaromatics. Among these, Cu-CoPc (2D MOFs with Cu2+ coordinated to CoPc) emerged as the most active catalyst, achieving a turnover frequency (TOF) value of 4726 h−1 for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Notably, this TOF value surpasses that of non-precious catalysts and is 180 times higher than that of commercial Pd/C (10 wt%).

Synthesis of phytogenically deposed Ag nanospheres on ZnO nanosheets for photocatalytic and catalytic applications

Current study presents the phytogenic deposition of metallic Ag nanospheres on ZnO nanosheets to produce Ag/ZnO nanostructures using Jacobaea Maritima (Silver Ragwort) plant extract and the prepared materials were tested for the photo-mineralization of methylene blue (MB) dye and catalytic reduction of nitroaromatics i.e. 4-nitroaniline (4-NA) and 4-nitrophenol (4-NP) in the presence of NaBH4 solution. The mean grain size and crystallinity of ZnO particles in Ag/ZnO nanostructures were found to be increased while the particle strain and dislocation density decreased with the elevation of Ag level in ZnO, and band gap energy value was reduced that has improved the photodegradation efficiency for MB dye from 45% to 98.60%, however, an excess amount of Ag has suppressed the photo-activity of Ag/ZnO nanostructures due to increase of band gap value and coverage of ZnO nanocrystals by Ag clusters. The catalytic reduction process indicated that the 4-NA and 4-NP were almost decolorized within 8 and 10 min, respectively. The degradation reaction rate of MB dye was enhanced by ∼7 times for Ag/ZnO nanostructures in comparison to pure ZnO nanosheets. The trapping experiments established that the •O2− and •OH radicals were the key active entities engaged in the deprivation of MB dye.

Pd/NHC catalyzed reduction and coupling of nitroaromatics for the synthesis of diarylamines.

Herein, we report a one-pot approach to diarylamines through the reductive homocoupling of nitroaromatics, employing triethylsilane as the reducing agent and Pd/NHC as the catalyst. This method enables nitroaromatics to serve both as electrophilic reagents and as precursors of nucleophilic reagents, allowing for the direct preparation of diarylamines without the need to isolate aromatic primary amines.

Flower-like MoS2 microspheres highly dispersed on CoFe2O4/MIL-101(Fe) metal organic framework: a recoverable magnetic catalyst for the reduction of toxic nitroaromatics in water

In this study, we report on the synthesis and characterization of novel magnetic MoS2/CoFe2O4/MIL101-(Fe) nanocomposite catalysts designed for the efficient reduction of toxic nitroaromatic compounds, such as nitrophenols and nitroanilines,...