Showing papers on "Nitrobenzene published in 2022"

Porous organic polymers for electrocatalysis.

Abstract: Porous organic polymers (POPs) composed of organic building units linked via covalent bonds are a class of lightweight porous network materials with high surface areas, tuneable pores, and designable components and structures. Owing to their well-preserved characteristics in terms of structure and composition, POPs applied as electrocatalysts have shown promising activity and achieved considerable advances in numerous electrocatalytic reactions, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, CO2 reduction reaction, N2 reduction reaction, nitrate/nitrite reduction reaction, nitrobenzene reduction reaction, hydrogen oxidation reaction, and benzyl alcohol oxidation reaction. Herein, we present a systematic overview of recent advances in the applications of POPs in these electrocatalytic reactions. The synthesis strategies, specific active sites, and catalytic mechanisms of POPs are summarized in this review. The fundamental principles of some electrocatalytic reactions are also concluded. We further discuss the current challenges of and perspectives on POPs for electrocatalytic applications. Meanwhile, the possible future directions are highlighted to afford guidelines for the development of efficient POP electrocatalysts.

Unprecedentedly high activity and selectivity for hydrogenation of nitroarenes with single atomic Co1-N3P1 sites

Abstract: Abstract Transition metal single atom catalysts (SACs) with M 1 -N x coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co 1 /NPC catalyst with unsymmetrical single Co 1 -N 3 P 1 sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co 1 -N 4 coordination, the electron density of Co atom in Co 1 -N 3 P 1 is increased, which is more favorable for H 2 dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co 1 -N 3 P 1 SAC exhibits a turnover frequency of 6560 h −1 , which is 60-fold higher than that of Co 1 -N 4 SAC and one order of magnitude higher than the state-of-the-art M 1 -N x -C SACs in literatures. Furthermore, Co 1 -N 3 P 1 SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.

Unprecedentedly high activity and selectivity for hydrogenation of nitroarenes with single atomic Co1-N3P1 sites

Abstract: Abstract Transition metal single atom catalysts (SACs) with M 1 -N x coordination configuration have shown outstanding activity and selectivity for hydrogenation of nitroarenes. Modulating the atomic coordination structure has emerged as a promising strategy to further improve the catalytic performance. Herein, we report an atomic Co 1 /NPC catalyst with unsymmetrical single Co 1 -N 3 P 1 sites that displays unprecedentedly high activity and chemoselectivity for hydrogenation of functionalized nitroarenes. Compared to the most popular Co 1 -N 4 coordination, the electron density of Co atom in Co 1 -N 3 P 1 is increased, which is more favorable for H 2 dissociation as verified by kinetic isotope effect and density functional theory calculation results. In nitrobenzene hydrogenation reaction, the as-synthesized Co 1 -N 3 P 1 SAC exhibits a turnover frequency of 6560 h −1 , which is 60-fold higher than that of Co 1 -N 4 SAC and one order of magnitude higher than the state-of-the-art M 1 -N x -C SACs in literatures. Furthermore, Co 1 -N 3 P 1 SAC shows superior selectivity (>99%) toward many substituted nitroarenes with co-existence of other sensitive reducible groups. This work is an excellent example of relationship between catalytic performance and the coordination environment of SACs, and offers a potential practical catalyst for aromatic amine synthesis by hydrogenation of nitroarenes.

High-valent cobalt-oxo species triggers hydroxyl radical for collaborative environmental decontamination

Abstract: The overlooked role of high-valent cobalt-oxo species (Co(IV)) in the Co(II)/peroxymonosulfate (PMS) process was uncovered recently using methyl phenyl sulfoxide (PMSO) as the probe. Herein, we further interestingly found that Co(IV) could trigger hydroxyl radical (•OH) formation, resulting in the oxidized products distribution of PMSO heavily relied on the relative concentration of PMSO. More significantly, the generation of a series of 18O-labeled hydroxylated products (i.e., hydroxylated methyl phenyl sulfone, nitrobenzene and 4-nitrobenzoic acid) in H218O conclusively verified that •OH was triggered by Co(IV) species. Density functional theory calculation demonstrated that Co(IV) initiated •OH formation via oxo ligand protonation-induced valence tautomerization. Moreover, the oxidative contribution of Co(IV) and •OH on organic degradation was specifically dependent on the type and concentration of the substrate. This study provided deeper insights into the evolution pathway of •OH mediated by Co(IV) species and enriched the understandings on the collaborative oxidation mechanism in Co(IV)-involved processes.

High-valent cobalt-oxo species triggers hydroxyl radical for collaborative environmental decontamination

Abstract: The overlooked role of high-valent cobalt-oxo species (Co(IV)) in the Co(II)/peroxymonosulfate (PMS) process was uncovered recently using methyl phenyl sulfoxide (PMSO) as the probe. Herein, we further interestingly found that Co(IV) could trigger hydroxyl radical (•OH) formation, resulting in the oxidized products distribution of PMSO heavily relied on the relative concentration of PMSO. More significantly, the generation of a series of 18O-labeled hydroxylated products (i.e., hydroxylated methyl phenyl sulfone, nitrobenzene and 4-nitrobenzoic acid) in H218O conclusively verified that •OH was triggered by Co(IV) species. Density functional theory calculation demonstrated that Co(IV) initiated •OH formation via oxo ligand protonation-induced valence tautomerization. Moreover, the oxidative contribution of Co(IV) and •OH on organic degradation was specifically dependent on the type and concentration of the substrate. This study provided deeper insights into the evolution pathway of •OH mediated by Co(IV) species and enriched the understandings on the collaborative oxidation mechanism in Co(IV)-involved processes.

Strong electronic interaction of indium oxide with palladium single atoms induced by quenching toward enhanced hydrogenation of nitrobenzene

Abstract: The realization of efficient and fully controllable synthesis of single atom catalysts is an exciting frontier, yet still challenging in the modern catalysis field. Here we describe a straightforward high-temperature quenching approach to precisely construct isolated palladium atoms supported over cubic indium oxide, with individual palladium atoms coordinated with four neighboring oxygen atoms. This palladium catalyst achieves exceptional catalytic efficiency in the selective hydrogenation of nitrobenzene to aniline, with more than 99% chemoselectivity under almost 100% conversion. Moreover, it delivers excellent recyclability, anti-CO poisoning ability, storage stability, and substrate tolerance. DFT calculations further reveal that the high catalytic activity stems from the optimized electronic structure and the charge states of palladium atoms in the defect-containing indium oxide. Our findings provide an effective approach to engineering single atom catalysts at the atomic level and open the door to a wide variety of catalytic reactions. • Pd single atoms supported over In 2 O 3 was created by a quenching approach. • DFT calculations reveal the support can provide anchoring sites for Pd atoms. • This catalyst shows high catalytic efficacy in hydrogenation of nitrobenzene. • The high catalytic activity stems from the unique coordination environment.

The promotion effect of π-π interactions in Pd NPs catalysed selective hydrogenation

Abstract: Abstract The utilization of weak interactions to improve the catalytic performance of supported metal catalysts is an important strategy for catalysts design, but still remains a big challenge. In this work, the weak interactions nearby the Pd nanoparticles (NPs) are finely tuned by using a series of imine-linked covalent organic frameworks (COFs) with different conjugation skeletons. The Pd NPs embedded in pyrene-COF are ca. 3 to 10-fold more active than those in COFs without pyrene in the hydrogenation of aromatic ketones/aldehydes, quinolines and nitrobenzene, though Pd have similar size and surface structure. With acetophenone (AP) hydrogenation as a model reaction, systematic studies imply that the π-π interaction of AP and pyrene rings in the vicinity of Pd NPs could significantly reduce the activation barrier in the rate-determining step. This work highlights the important role of non-covalent interactions beyond the active sites in modulating the catalytic performance of supported metal NPs.

Nano-pyramid-type Co-ZnO/NC for hydrogen transfer cascade reaction between alcohols and nitrobenzene

Abstract: The catalytic hydrogen transfer (CHT) cascade reaction between alcohols and nitro- compounds meets green chemistry yet involves high catalyst requirements. Herein, a hierarchical nano-pyramid structure, in which cobalt single atoms (Co SAs) are deposited on highly dispersed ZnO nanoparticles supported by nitrogen-doped carbon (denoted as Co-ZnO/NC), was designed and obtained through pyrolysis of ZnCo-ZIF. The catalyst exhibited excellent catalytic performance toward the CHT cascade reaction, achieving a high nitrobenzene conversion (94 %), imine selectivity (97 %), and turnover frequency (8.8 h−1). This nano-pyramid is a state-of-the-art non-noble-metal catalyst and is comparable to noble-metal catalysts. Experimental and DFT results revealed that the Co SAs supported on ZnO reduced the reaction energy barrier of hydroxyl dehydrogenation, the first and rate-determining step in this heterogeneous catalysis. Furthermore, Co-ZnO/NC exhibits good recyclability and universality. Our findings offer a new catalyst for Schiff base synthesis and aid understanding of the roles of Zn in ZIF-derived carbon catalysts.

Hazard assessment of the thermal stability of nitrification by-products by using an advanced kinetic model

Abstract: Since the 1990 s, sporadic explosion accidents have occurred in the chemical industry. Accidents related to nitrification reactions or nitrification substances have had the most severe consequences. One reason for this phenomenon is the high risk of nitrification by-products, which are liable to combust and explode. Special attention must be paid to the production, collection, storage, and disposal of nitrification by-products. This study examined the thermal stabilities of the phenolic by-products created during nitrobenzene formation. The thermal stabilities of three representative aromatic nitrophenol by-products were determined using differential scanning calorimetry, accelerating rate calorimetry, and thermogravimetric analysis. Advanced thermodynamic models were established for calculation and fitting, which provided reliable data support for exploring the intrinsic stability of nitrification by-products.

Photocatalytic Multielectron Reduction of Nitroarenes to Anilines by Utilizing an Electron-Storable Polyoxometalate-Based Metal-Organic Framework.

Abstract: A powerful approach to generate photocatalysts for the highly selective reduction of nitrobenzene using light as the driving force is a combination of photosensitizers and electron-storable components in a cooperative photocatalysis fashion. Herein, a new precious metal-free photocatalyst, {ZnW-TPT}, was prepared by incorporating a Zn-substituted monovacant Keggin polyanion [SiZnW11O39]6- and a photoactive organic bridging link 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) into a framework. In this structure, the direct coordination bond between [SiZnW11O39]6- and the TPT ligand and the π-π interactions between TPT molecules help separate and migrate photogenerated carriers, which improves the photocatalytic activity of {ZnW-TPT}. The photoelectrochemical properties of {ZnW-TPT} were well studied by solid UV-vis absorption, fluorescence, transient photocurrent response, and electrochemical impedance spectroscopy tests. {ZnW-TPT} efficiently converts using hydrazine hydrate with 99% conversion and 99% selectivity for anilines under mild conditions.

Nano-pyramid-type Co-ZnO/NC for hydrogen transfer cascade reaction between alcohols and nitrobenzene

Abstract: The catalytic hydrogen transfer (CHT) cascade reaction between alcohols and nitro- compounds meets green chemistry yet involves high catalyst requirements. Herein, a hierarchical nano-pyramid structure, in which cobalt single atoms (Co SAs) are deposited on highly dispersed ZnO nanoparticles supported by nitrogen-doped carbon (denoted as Co-ZnO/NC), was designed and obtained through pyrolysis of ZnCo-ZIF. The catalyst exhibited excellent catalytic performance toward the CHT cascade reaction, achieving a high nitrobenzene conversion (94 %), imine selectivity (97 %), and turnover frequency (8.8 h−1). This nano-pyramid is a state-of-the-art non-noble-metal catalyst and is comparable to noble-metal catalysts. Experimental and DFT results revealed that the Co SAs supported on ZnO reduced the reaction energy barrier of hydroxyl dehydrogenation, the first and rate-determining step in this heterogeneous catalysis. Furthermore, Co-ZnO/NC exhibits good recyclability and universality. Our findings offer a new catalyst for Schiff base synthesis and aid understanding of the roles of Zn in ZIF-derived carbon catalysts.

Oxygen Vacancy-Mediated CuCoFe/Tartrate-LDH Catalyst Directly Activates Oxygen to Produce Superoxide Radicals: Transformation of Active Species and Implication for Nitrobenzene Degradation.

Abstract: Oxygen vacancies play a vital role in the catalytic activity of layered double hydroxide (LDH) catalysts in wastewater treatment. However, the mechanism of oxygen vacancy-mediated LDH-activated oxygen to produce reactive oxygen species (ROS) still lacks a reasonable explanation. In this work, a tartrate-modified CuCoFe-LDH (CuCoFe/Tar-LDH) with abundant oxygen vacancies was designed, which can efficiently degrade nitrobenzene (NB) under room conditions. The technical energy consumption is 0.011 kW h L-1. According to the characterization and calculation results, it is proposed that oxygen vacancies are formed because of the oxygen deficiency which is caused by the reduction of the energy between the metal ion and oxygen, and the metal ion transitions to a lower state. Compared with CuCoFe-LDH, the oxygen vacancy formation energy of CuCoFe/Tar-LDH decreased from 1.98 to 1.13 eV. The O2 bond length adsorbed on the oxygen vacancy is 1.27 Å, close to the theoretical length of superoxide radicals (•O2-) (1.26 Å). Radical trapping experiments and electron spin-resonance spectroscopy spectrum prove that •O2- is an important precursor of •OH. This work is dedicated to the in-depth exploration of the oxygen vacancy-mediated CuCoFe/Tar-LDH catalyst activation mechanism for molecular oxygen and the conversion relationship between ROS.

Predominant Catalytic Performance of Nickel Nanoparticles Embedded into Nitrogen-Doped Carbon Quantum Dot-Based Nanosheets for the Nitroreduction of Halogenated Nitrobenzene

Abstract: A novel structure of a porous carbon–metal composite was designed and constructed from nitrogen-doped carbon quantum dots (NCQDs) and Ni. NCQDs (3–5 nm) with rich surface groups adsorbed with Ni ions can assemble into a carbon flake structure (50–60 nm) via atomic bonding, in which Ni is effectively dispersed and separated by NCQDs. Thus, a porous carbon nanosheet uniformly inlaid with metal nanoparticle (Ni@NCQDs) was built by subsequent thermal treatment. As a robust catalyst, Ni@NCQDs can promote the nitroreduction of p-chloronitrobenzene to p-chloroaniline with high activity (100%) and selectivity (99.8%) at 4.28 times the reaction rate of commercial Raney Ni. The electron transfer between Ni nanoparticles and porous carbon nanosheets over the N–Ni interface is responsible for the excellent performance. Besides, the wide applicability of Ni@NCQDs for various nitroarenes suggests that Ni@NCQDs have a potential to replace industrial catalysts (noble metal and Raney Ni). These findings confirm that the NCQDs, as an excellent carbon material, demonstrates a promising prospect of application in improving the catalytic performance of Ni-based catalysts.

Tuning the Electron Density of Metal Nickel via Interfacial Electron Transfer in Ni/MCM-41 for Efficient and Selective Catalytic Hydrogenation of Halogenated Nitroarenes

Abstract: Catalytic hydrogenation of nitrocompound is an environment-benign strategy for the production of important aniline intermediates. Herein, MCM-41 was synthesized from sepiolite via an in situ self-assembled method, and the modified MCM-41 supported nickel-based catalysts were prepared and applied in halogenated nitrobenzene hydrogenation to halogenated aniline. As compared to Ni/MCM-41, the Sn- or La-modified MCM-41 supported nickel-based catalysts exhibited better catalytic performance. The electron transfer from Sn or La species to Ni led to a downshift in the d-band center of Ni, which was in favor of H desorption and hence promoted hydrogenation activity. It was found that chloronitrobenzene preferred the tilted adsorption orientation mode on the surface of Ni–Sn and Ni–La2O3 to flat adsorption orientation. Moreover, the C–Cl bond scission on Ni–Sn and Ni–La2O3 was thermodynamically unfavorable in comparison with pure-phased Ni, leading to higher selectivity to chloroaniline. Ni/LaMCM-41-NH2 gave the best catalytic performance of 100% conversion and 99.6% selectivity to m-chloroaniline.