Reduction Of Nitroaromatics Research Articles

Highly stable and uniform colloidal silver quantum dots stabilized with (N,S,O) donor ligand: Selective sensing of Hg(II)/Cu(II) and I− ions and reduction of nitro-aromatics in water

The present paper showed the role of ligand inthe effective stabilization of colloidal silver-quantum dots (Ag-QDs) and their applications for the colorimetric detection of metal ions/anions. Furthermore, the Ag-QDs have been explored to reduce nitroaromatics, industrial waste and pollutants. The donor atoms such as (N,S,O) present on ligands have been found to stabilize the Ag-QDs in the colloidal state effectively, and the pendant alkyl chain governs their uniform dispersion. The QDs (size ∼ 5 nm) are highly stable and can be kept in the colloidal state without aggregation for months under ambient conditions. The Ag-QDs showed naked-eye colorimetric sensing of Hg(II)/Cu(II) and I− ions selectively over other ions at very low concentrations. The colorimetric change has been attributed due to cation and anion-mediated aggregation of QDs. Furthermore, these QDs have also been found effective for reducing various nitroaromatics into valuable amines in a very short time and showed first-order kinetics with the calculated rate of 0.1352 min−1. The Hammett plot suggests that the reaction rate depends on the groups present at the para-position to the nitro group with a negative slope of − 1.291 which indicates that the reaction is proceedingviathe formation of a cationic intermediate. The results described in this paper will be the pioneer in the field of designing of new ligands for the effective stabilization of metal nanoparticles in the colloidal state without altering their activity.

Removable Visible-Light photocatalysts for Nitro-group reduction constructed from palladium decorated Ti-MOFs integrate onto fibers

An effective and recyclable photocatalyst composite made of metal/metal organic framework/cellulose fiber (Pd/MIL-125-NH2/CF) was thoroughly examined. Nano-palladium was added to the MIL-125-NH2 present in the fibre. Pd/MIL-125-NH2/CF composites was shown a noticeably greater photocatalytic performance for nitro-aromatics reduction when exposed to visible light as compared to MIL-125-NH2/CF. When Pd/MIL-125-NH2/CF composite was utilised, 80.6–93.5 % of p-nitrophenol was photoreduced after 60 min. The percentage of p-nitrophenol's photoreduction activity was reduced to 54.4–62.0 after 5 recycles. The prepared Pd/MIL-125-NH2/CF composites were shown highly antimicrobial properties, confirming the idealism of photocatalyst uses. The Pd/MIL-125-NH2/CF composite has an effective photocatalyst for the reduction of nitro-aromatics in visible light, showing its potential performance in producing intermediates used in various industrial products.

Visible-Light-Driven Porphyrin-Based Bimetallic Metal–Organic Frameworks for Selective Photoreduction of Nitro Compounds under Mild Conditions

Selective reduction of nitroaromatics to the corresponding amines generally requires complex conditions, involving pressurized hydrogen, higher temperatures, or organic acids. In this work, we successfully prepared a series of porphyrin-based MOF photocatalysts (Pd-PMOFs, In-PMOFs, and In/Pd-PMOFs) via a facile solvothermal method for the efficient selective reduction of nitroaromatics to corresponding anilines with deionized water as the hydrogen donor. Being a new structured material (monoclinic, C52H40InN6O8Pd), on account of the abundant pore channels, strong light absorption capability, well-matched bandgap, as well as the coordination of indium ions and palladium ions, In/Pd-MOFs have excellent migration efficiency of photo-induced electrons and holes. Specifically, the In/Pd-PMOF photocatalyst manifested superior conversion (100%) and selectivity (≥80%) toward the screened nitro compounds under mild conditions. This work avoids the use of strong reductants, organic acids, and pressurized hydrogen gas as hydrogen sources, providing a promising concept for developing green catalytic systems.

Facile and green fabrication of copper‐based magnetically recoverable yolk–shell nanocatalysts with high catalytic performance for nitroaromatic reduction

A simple method was reported to achieve a green yolk–shell Fe3O4@SiO2@CuO nanocatalysts (YS‐Fe3O4@SiO2@CuO). Glucose (G) and lactose (L), as a grafting agent, were applied for decorating CuO on the magnetic nanoparticles surface and then using calcination method, yolk–shell structure was obtained. Characterization of nanocatalysts was carried out using inductively coupled plasma–optical emission spectrometry (ICP‐OES), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX)‐Mapping, thermogravimetric analysis (TGA), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), Brunauer, Emmett, and Teller (BET), and vibrating sample magnetometer (VSM) analyses and the results confirmed the successful synthesis of these catalysis. The activity of the nanocatalysts were studied to reduce nitroaromatic compounds monitoring by UV–Vis spectra. In the model reaction, 4‐nitrophenol was reduced using YS‐Fe3O4@SiO2@CuO(G) and YS‐Fe3O4@SiO2@CuO(L), with the activity factors (k′) of 3218 and 2023 s−1 g−1, and rate constants (Kapp) of 0.56 and 1.19 min−1, respectively. The advantages of prepared nanocatalysts were good stability and high conversion. The magnetic property of nanocatalysts makes them easy to recover in multiple cycles.

Spin-glass behavior and redox catalytic properties of room temperature produced ZnCrMnO4

Recognizing the multifunctional capability of spinels, synthesis, and properties of oxide spinel with an equal concentration of Jahn Teller active Mn 3+ and geometrically frustrated Cr 3+ with non-magnetic Zn 2+ have been explored. ZnCrMnO 4 , resulting from the room temperature oxidation reaction, has an average crystallite size of 16 nm. Nearly 25% of Zn occupies the octahedral sites along with Cr and Mn, as revealed by the successful structural refinement in the Fd-3m space group. Electron microscopic results confirm cubic spinel formation. Raman spectrum shows the disordered nature of the spinel. X-ray photoelectron spectral (XPS) analysis establishes mixed valences of manganese ((III), (IV)) and chromium ((III) and (VI)). ZnCrMnO 4 displays electronic transitions typical of Mn 3+ and Cr 3+ in its UV–Visible diffuse reflectance spectrum. Spin-glass frustration at 26 K, followed by an antiferromagnetic ordering at 10 K, is noticed for the sample from the magnetic measurements. The sample exhibits a surface area of 138 m 2 /g (BET measurements) and catalyzes the oxidation of aromatic alcohols (phenol, benzyl alcohol) and reduction of nitroaromatics efficiently.

Photocatalytic reduction of nitrobenzene to aniline over CdS nanorods: the impacts of reaction conditions and the hydrogenation mechanism

The effects of the reaction conditions and the hydrogenation mechanism of nitrobenzene over noble metal modified CdS nanorods were investigated to enrich the deep understanding of the photocatalytic reduction of nitroaromatics to anilines.

Co(dppbsa)-catalyzed reductive N,N-dimethylation of nitroaromatics with CO2 and hydrosilane

A novel half-sandwich Co(dppbsa) ([Co]) was synthesized and employed for the catalytic N,N-dimethylation of nitroaromatics with CO2 and hydrosilane. The same catalyst also enabled the highly efficient reduction of nitroaromatics to aromatic amines.

Preparation of novel magnetic noble metals supramolecular composite for the reduction of organic dyes and nitro aromatics

By considering the exceptional properties of supramolecular, noble metals (NM) and magnetic nanoparticles (NPs), we successfully synthesized a novel magnetic, metals and supramolecular composite. Briefly, the Fe3O4@SiO2 core-shell spheres were first modified with gold (Au) and palladium (Pd) NPs and then with mono-6-thio-β-cyclodextrin (SH-β-CD). The synthesized Fe3O4@SiO2-Au-Pd@SH-β-CD nanocomposite shows a good magnetic response (42.3 emu/g). The nanocomposite showed good performance for the reductive degradation of rhodamine B (RhB) and 4-nitrophenol (4-NP). The calculated rate constant (k) values for the reduction of 4-NP and RhB were 0.062± 0.02 s−1 and 0.027± 0.01 s−1, respectively. The high catalytical performance was supposed to be due to the host-guest interaction of β-CD and also due to the NM synergic effect. The nanocomposite structural and chemical morphology was investigated by various spectroscopic techniques. Furthermore, the catalyst was recycled six times and it maintains morphology, chemical nature, and high magnetic behavior, as demonstrated by FTIR and TEM analysis of the recycled catalyst. These results demonstrate a very efficient, cost-effective, and recyclable catalyst in the field of catalysis technology development.

Oxygen-insensitive nitroreductase E. coli NfsA, but not NfsB, is inhibited by fumarate.

Escherichia coli NfsA and NfsB are founding members of two flavoprotein families that catalyze the oxygen-insensitive reduction of nitroaromatics and quinones by NAD(P)H. This reduction is required for the activity of nitrofuran antibiotics and the enzymes have also been proposed for use with nitroaromatic prodrugs in cancer gene therapy and biocatalysis, but the roles of the proteins in vivo in bacteria are not known. NfsA is NADPH-specific whereas NfsB can also use NADH. The crystal structures of E. coli NfsA and NfsB and several analogs have been determined previously. In our crystal trials, we unexpectedly observed NfsA bound to fumarate. We here present the X-ray structure of the E. coli NfsA-fumarate complex and show that fumarate acts as a weak inhibitor of NfsA but not of NfsB. The structural basis of this differential inhibition is conserved in the two protein families and occurs at fumarate concentrations found in vivo, so impacting the efficacy of these proteins.

In Situ Construction of Single-Site Ti Active Centers on Carbon Nitride for Photocatalytic Chemoselective Hydrogen Transfer Reduction

In this work, we report an in situ construction of single-site Ti active centers on a carbon nitride surface during photocatalytic processes for one-pot chemoselective hydrogen transfer reduction of nitroaromatics and domino-type reaction using Cp2TiCl2 and −OH-enriched carbon nitride (OHCN) as precatalysts. Due to the selective adsorption of nitro and the promotion of photogenerated charge transfer by single-site Ti active species and the formation of Ti3+, the system can achieve an efficient chemoselective reduction of nitroaromatics containing various substituents, especially sensitive substituents (C═C, C≡C, C═O, C═N, C≡N, C–X (X is halogen), etc.). The two processes of chemoselective reduction of nitroaromatics and oxidation of aromatic alcohols are photocatalytically coupled to form a complete photocatalytic cycle, which allows the simultaneous formation of two high-value-added products, aromatic amines and aromatic aldehydes. More valuable products like imines are obtained by effecting the reduction of the nitro moiety to −NH2 in the presence of aromatic alcohols that can react in a domino-type process. This work guides the in situ preparation of non-noble metallic single-site photocatalysts and provides a strategy for the photocatalytic synthesis of valuable organic compounds from nitroaromatics.

β-cyclodextrin functionalized gold nanoparticles as an effective nanocatalyst for reducing toxic nitroaromatics

We demonstrated the effective reduction of the organic pollutants, the nitroaromatics, via green sustainable chemistry using high efficacy of the catalytic materials, i.e., β-cyclodextrin (β-CD) functionalized Au nanoparticles (AuNPs). Eco-friendly and biocompatible techniques were employed to fabricate gold nanoparticles (AuNPs) from an Au precursor (HAuCl4) using β-CD that plays as both reducing and surface-functionalizing agents. Detailed investigation of β-CD AuNPs formation, their sizes with morphologies, the surface charge, and the hydrodynamic size in a colloidal medium were performed by ultraviolet–visible (UV–vis) absorbance spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Zeta potential measurements, and the dynamic light scattering analysis, respectively. The plasmonic nanoparticle formation of the β-CD AuNPs led to the strong localized surface plasmon resonance peak at around the 520 nm wavelength. The catalytic activity of the β-CD AuNPs was evaluated using model reactions, including the catalytic conversion of nitroaromatics to the corresponding amino-aromatic compounds upon mixing sodium borohydride in a water medium. Chemical reactions of such catalytic reduction of nitroaromatics were tracked by UV–vis absorbance spectroscopy, showing high catalytic activity of β-CD AuNPs. We also provided a discussion on the possible pathways for the AuNPs-mediated catalytic reduction of nitroaromatics. The efficacy of the nanocatalysts presented to reduce nitroaromatics can hold a potential promise for detoxifying aquatic environments and their pharmaceutical applications.

Eco-friendly synthesis, characterization, catalytic, antibacterial, antidiabetic, and antioxidant activities of Embelia robusta seeds extract stabilized AgNPs

The current research study is to develop and easy and eco-friendly method for the synthesis of AgNPs using aqueous seed extract of Embelia robusta (Er-AgNPs) and evaluated the extract to know the effects of catalytic, anti-bacterial, anti-diabetic, and anti-oxidant activity. Er-AgNPs were characterized via several techniques including UV-vis absorption, PL, XRD, FTIR, and TEM UV-vis study confirmed the formation of Er-AgNPs. Face centered cubic (FCC) crystal structure of biosynthesized Er-AgNPs was governed by the XRD analysis. FTIR study confirmed the presence of OH and NH functional groups of secondary molecules of seed extract capped on the AgNPs surface. The produced Er-AgNPs were dark brown in color with almost spherical shape in the size ranging from 5 to 15 nm. The presence of Er-AgNPs (1 mL) exhibited considerably enhanced dyes degradation (CY, 95.12% and EY, 97.82% in 18 min), antibiotics degradation (TC, 96.45% and CIP, 98.01% in 21 min), and nitroaromatics reduction (4-NP, 88.12% and 4-NA, 92.45% in 15 min). The Er-AgNPs have showed significant antibacterial activity on multi drug resistance bacteria. The synthesized Er-AgNPs exhibited strong antioxidant activities for the DPPH assay. Remarkable anti-diabetic (α-glucosidase, α-amylase, and HbA1C) activities were noticed for biosynthesized Er-AgNPs. This is the first report on the biosynthesis of AgNPs using seeds extract of Embelia robusta. • Eco-friendly synthesis of AgNPs were carried out using Embelia robusta seeds extract. • The synthesized Er-AgNPs were found to be fcc structure and average diameter is 8±2 nm. • Biosynthesized Er-AgNPs exhibited excellent catalytic activity for the degradation of dyes, antibiotics, and nitrocompounds reduction at low NaBH 4 content. • Biogenic Er-AgNPs showed good antibacterial, antidiabetic and antioxidant activities. • Er-AgNPs were developed as a four-in-one platform for the environmental remediation of waste water treatment and biological applications.

Ultrarapid and highly efficient reduction of nitroaromatic compounds using cyclodextrin MOF

Herein, a metal-organic framework (Cu-β-CD-MOF) was prepared that incorporates copper (Cu) and beta-cyclodextrin (β-CD) via vapor diffusion. Cu-β-CD-MOF was employed as a catalyst for the reduction of various nitroaromatics (NACs) compounds viz. 4-Nitrophenol(4-NP), Nitrobenzene (NB), 2-Nitrophenol(2-NP) and 4-Nitroaniline(4-NA). Cu-β-CD-MOF was analyzed using diverse techniques, which disclosed a narrow band gap (2.23 eV), enhanced thermal stability, and rod-like crystal morphology. Cu-β-CD-MOF exhibited high catalytic activity, reducing all NACs in 4 min. As a result of its high photocatalytic efficiency, low cost, non-toxic, and adherence to green chemistry principles, Cu-β-CD-MOF could be considered for wastewater treatment applications.

Controllable synthesis of oxygenated carbon supported palladium nanodendrites for highly efficient nitroaromatics reduction

Palladium nanodendrites supported on oxygenated carbon layer (Pd/ O-carbon) have been prepared herein through modulating the mass ratio of Pd (II) precursor and carbon dots derived from sucrose without additional reducing agent. Characterizations of FT-IR, XPS spectra and TEM graphs reveal that oxygen-bearing groups on carbon dots play important role in reducing Pd(II) into Pd(0), controlling nanoparticle growth and stabilizing Pd nanodendrites. The as-prepared Pd/ O-carbon presents size-dependent activity on catalytic p-nitrophenol (4-NP) reduction using NaBH4 as hydrogen donor. The reaction rate constant of 4-NP on Pd/ O-carbon with Pd particle size of 4–7 nm almost triples that on catalyst with Pd nanoparticles of 6–10 nm. Pd / O-carbon can be reused for 10 times without obvious decreased activity, showing a long-term chemical stability in 4-NP reduction reaction. In addition, Pd / O-carbon achieves ∼100% selectivity on nitrobenzene conversion and > 95% selectivity for the hydrogenation of substituted nitrobenzene compounds with methyl-, chloro- and amino- groups to corresponding aniline through tandem reaction with NH3BH3 as hydrogen donor in methanol/ water solvent (volume ratio of 1:3).

Synthesis of Prussian Blue Analogue and Its Catalytic Activity toward Reduction of Environmentally Toxic Nitroaromatic Pollutants.

Nitroanilines are environmentally toxic pollutants which are released into aquatic systems due to uncontrolled industrialization. Therefore, it is crucial to convert these hazardous nitroanilines into a harmless or beneficial counterpart. In this context, we present the chemical reduction of 4-nitroaniline (4-NA) by NaBH4 utilizing Prussian blue analogue (PBA) as nanocatalyst. PBAs can serve as inexpensive, eco-friendly, and easily fabricated nanocatalysts. PBA cobalt tetracyanonickelate hexacyanochromate (CoTCNi/HCCr) was stoichiometrically prepared by a facile chemical coprecipitation. Chemical, phase, composition, and molecular interactions were investigated by XRD, EDX, XPS, and Raman spectroscopy. Additionally, SEM and TEM micrographs were utilized to visualize the microstructure of the nanomaterial. The findings revealed the synthesized PBA of the cubic phase and their particles in nanosheets. The band gap was estimated from the optical absorption within the UV-vis region to be 3.70 and 4.05 eV. The catalytic performance of PBA for the reduction of 4-NA was monitored by UV-vis spectroscopy. The total reduction time of 4-NA by PBA was achieved within 270 s, and the computed rate constant (k) was 0.0103 s-1. The synthesized PBA nanoparticles have the potential to be used as efficient nanocatalysts for the reduction of different hazardous nitroaromatics.

Research Progress and Prospects of Spinel Ferrite Nanostructures for the Removal of Nitroaromatics from Wastewater

Spinel ferrite nanostructures have played significant roles in the development of materials science and technology. Spinel ferrite nanostructures possess not only promising magnetic properties but also high resistivity, stability, and low eddy current losses. The recent progress in the utilization of spinel ferrite nanostructures for water remediation is reviewed with special emphasis on the adsorption, transformation, degradation, and catalytic reduction of nitroaromatics. Then, the structure–property relationships and design considerations of spinel ferrite nanostructures for catalytic applications are discussed in detail. Insights into the details of the various removal processes on the model spinel ferrite nanostructures are provided with a basic concept of nitroaromatics remediation. Subsequently, reaction kinetics and mechanisms are classified and their advantages and disadvantages are described. Lastly, challenges and future perspectives of spinel ferrite nanostructures for their practical applications are presented. With further advancement, spinel ferrites have potential to be practically utilized for a wide range of applications such as water treatment plants.

Steering bi-directional charge transfer via non-conjugated insulating polymer

Exquisite tuning of spatial charge transfer and separation has been an enduringly core issue in heterogeneous photocatalysis. Nevertheless, precise modulation of directional charge transfer to the ideal catalytically active sites remains challenging owing to rapid recombination rate of photoinduced charge carriers and sluggish charge transfer kinetics. Herein, bi-directional spatially separated electron and hole transport channels were simultaneously constructed over transition metal chalcogenides (TMCs)-based heterostructures via an efficient and facile electrostatic self-assembly strategy. Tailor-made positively charged non-conjugated polymer of branched polyethyleneimine (BPEI) and negatively charged metal nanocrystals (NCs) building blocks were controllably anchored on the TMCs substrate. We found that electrons photoexcited over TMCs substrate can migrate spontaneously, smoothly and unidirectionally to the tightly integrated neighboring metal NCs, wherein metal NCs function as Schottky-type electron-trapping reservoirs and the ultra-thin intermediate BPEI layer serves as a directional hole transport mediator, thus synergistically contributing to the significantly enhanced charge separation and prolonged charge lifetime. Benefiting from these merits, such self-assembled TMC@BPEI/metal heterostructure exhibits the markedly enhanced photoreduction catalysis toward photocatalytic hydrogen generation and anaerobic selective reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would provide inspiring idea for fine modulation of charge separation and transfer toward solar-to-chemical energy conversion.

Functionalized silica nanoporous Pd complex for reduction of nitroarenes and dyes

Pd adorned on SBA-Pr-3AP ([email protected]) was investigated as a catalyst for the degradation of natural, synthetic organic dyes, and the reduction of nitroarenes by NaBH4 as a reducing agent with recyclability and regeneration procedure was discerned which may open up new avenues for remediation of aqueous pollutants. The degradation of dangerous dyes such as methylene blue, methyl orange, and natural colors from pomegranate (PM) and opuntia (OP), and the reduction of nitroaromatics at ambient temperature, were studied. The primary materials of numerous medications, agrochemicals, pigments, and colors are anilines, one of the crucial chemical feedstocks. In this perspective, the method for providing aniline derivatives is the catalytic reduction of nitro. An effective catalyst demonstrated to be extremely effective for the reduction of nitroarenes into various amines.

Phosphorous‐modified Porous Carbon Supported Nickel Nanoparticles as a Catalyst for the Reduction of Nitroaromatics in Water

AbstractPhosphorus‐modified porous carbon (PCP) with about 7 w% phosphorus content has been prepared from acetylene and triphenylphosphine using chemical vapor deposition method. Then, 5, 10, 15, 20, 25, and 30 w% nickel(0) nanoparticles have been deposited (using the in‐situ reduction of NiCl2 salt) on the surface of PCP to obtain Ni‐decorated PCP (NPCP). The prepared materials (NPCP) have been employed as a catalyst for the catalytic reduction of nitrobenzene derivatives to anilines. The NPCP with 20 w% of Ni showed the highest catalytic efficiency. The reaction was carried out using 10 mg catalyst, 2 mL of 25 % hydrazine hydrate solution as the reducing agent in 2 h (optimized conditions) to obtain the product in 51–100 % yield. To show the versatility of this method, 8 nitrobenzene derivatives (including 3 different nitrophenols) have been successfully reduced using this method. The recyclability of the catalyst was investigated and the results showed only 20 % decreasing in the yield after 6 runs.

Synthesis of boron nitride nanosheets incorporated with Pd nanoparticles for reduction of nitroaromatics

Synthesis of boron nitride nanosheets incorporated with Pd nanoparticles for reduction of nitroaromatics