Isolated Iron Single-Atomic Site-Catalyzed Chemoselective Transfer Hydrogenation of Nitroarenes to Arylamines

Theoretical study on nitrobenzene hydrogenation to aniline catalyzed by M1/CeO2-x(111) single-atom catalysts

The hydrogenation of nitrobenzene to aniline is a critical process in the production of numerous chemical intermediates and pharmaceuticals. Developing efficient catalysts for this reaction is essential to improve reaction rates and selectivity. A density functional theory (DFT) study was performed to investigate the catalytic activity of twelve late transition metal-doped ceria (M1/CeO2-x(111)) single-atom catalysts for the hydrogenation of nitrobenzene to aniline. Firstly, the stabilities and oxidation states of doped metal atoms on M1/CeO2-x(111) surfaces were studied. Subsequently, the reactivity of two possible rate-determining steps on M1/CeO2-x(111) surfaces, H2 dissociation and the fourth hydrogen transfer step in the direct route of nitrobenzene hydrogenation (PhNHO* + H* → PhNHOH*), was further investigated. The Brønsted-Evans-Polanyi (BEP) relationship between reaction energies (ΔE) and activation energies (Ea) and the volcano plot between the energies of PhNHOH* (EPhNHOH*) and the activation energies (Ea) of the fourth hydrogen transfer step were identified. The calculated results indicate that the fourth hydrogen transfer step is the rate-determining step in the overall reaction, and that the Ru1/CeO2-x(111) single-atom catalyst could be one of the most promising catalysts with good catalytic activity for the nitrobenzene hydrogenation.

Effects of oxygen vacancies on hydrogenation efficiency by spillover in catalysts

Hydrogen spillover is crucial for hydrogenation reactions on supported catalysts. The properties of supports have been reported to be very important for affecting hydrogen spillover and the subsequent hydrogenation process. The introduction of oxygen vacancies offers a promising strategy to enhance efficiency of catalysts. Recent advanced characterization and theoretical modeling techniques have provided us with increasing new insights for understanding hydrogen spillover effects. However, a comprehensive understanding of oxygen vacancy effects on hydrogen spillover and hydrogenation efficiency of catalysts is still lacking. This review focuses on the recent advances in support effects especially oxygen vacancy effects on improving the efficiency of catalysts from three process aspects including hydrogen dissociation, active hydrogen spillover, and hydrogenation by spillover. The challenges in studying the effects on hydrogenations by spillover on the supported catalysts are highlighted at the end of the review. It aims to provide valuable strategies for the development of high-performance catalytic hydrogenation materials.

Atomically dispersed iron sites from eco-friendly microbial mycelium as highly efficient hydrogenation catalyst

Iron, one of the most abundant elements on earth and an essential element for living organisms, plays a crucial role in our daily metabolism. In the field of catalysis, the development of high-performance catalysts based on less toxic iron element is also of significant importance for green chemistry and a sustainable future. To construct Fe-based heterogeneous catalysts with excellent hydrogenation performance, precise modulation of the atomic coordination structure is a key strategy for enhancing catalytic activity. In this study, we present an in-situ coating method for applying a zeolitic imidazolate framework (ZIF) onto the surface of fungal hyphae. The asymmetric coordination structure of Fe1-N3P1 was precisely tailored by utilizing the phosphorus source from the fungus and the nitrogen source in the ZIFs. Detailed characterizations and density functional theory calculations revealed that the incorporation of ZIFs not only increased the specific surface area of catalysts, but also facilitated the dispersion of Fe2P nanoparticles into the Fe1-N3P1 center, making the lowest reaction energy barrier and resulting in the best performance for nitrobenzene hydrogenation when compared to the Fe2P nanoparticles and clusters. This research introduces a novel design concept for constructing asymmetric monoatomic configuration based on the inherent characteristics of natural microorganisms and the exogenous porous coordination polymers.

The Facile Production of p-Chloroaniline Facilitated by an Efficient and Chemoselective Metal-Free N/S Co-Doped Carbon Catalyst

The catalytic hydrogenation of the toxic and harmful p-chloronitrobenzene to produce the value-added p-chloroaniline is an essential reaction for the sustainable chemical industry. Nevertheless, ensuring satisfactory control of its chemoselectivity is a great challenge. In this work, a N/S co-doped metal-free carbon catalyst has been fabricated by using cysteine as a source of C, N, and S. The presence of calcium citrate (porogen agent) in the mixture subjected to pyrolysis provided the carbon with porosity, which permitted us to overcome the issues associated with the loss of heteroatoms during an otherwise necessary activation thermal treatment. Full characterization was carried out and the catalytic performance of the metal-free carbon material was tested in the hydrogenation reaction of p-chloronitrobenzene to selectively produce p-chloroaniline. Full selectivity was obtained but conversion was highly dependent on the introduction of S due to the synergetic effect of S and N heteroatoms. The N/S co-doped carbon (CYSCIT) exhibits a mesoporous architecture which favors mass transfer and a higher doping level, with more exposed N and S doping atoms which act as catalytic sites for the hydrogenation of p-chloronitrobenzene, resulting in enhanced catalytic performance when compared to the N-doped carbon obtained from melamine and calcium citrate (MELCIT) used as a reference.

Preparation and Application of Single-Atom Cobalt Catalysts in Organic Synthesis and Environmental Remediation

The development of high-performance catalysts plays a crucial role in facilitating chemical production and reducing environmental contamination. Single-atom catalysts (SACs), a class of catalysts that bridge the gap between homogeneous and heterogeneous catalysis, have garnered increasing attention because of their unique activity, selectivity, and stability in many pivotal reactions. Meanwhile, the scarcity of precious metal SACs calls for the arrival of cost-effective SACs. Cobalt, as a common non-noble metal, possesses tremendous potential in the field of single-atom catalysis. Despite their potential, reviews about single-atom Co catalysts (Co-SACs) are lacking. Accordingly, this review thoroughly summarized various preparation methodologies of Co-SACs, particularly pyrolysis; its application in the specific domain of organic synthesis and environmental remediation is discussed as well. The structure-activity relationship and potential catalytic mechanism of Co-SACs are elucidated through some representative reactions. The imminent challenges and development prospects of Co-SACs are discussed in detail. The findings and insights provided herein can guide further exploration and development in this charming area of catalyst design, leading to the realization of efficient and sustainable catalytic processes.

Design and Synthesis of N-Doped Carbons as Efficient Metal-Free Catalysts in the Hydrogenation of 1-Chloro-4-Nitrobenzene

Metal-free catalysts based on nitrogen-doped porous carbons were designed and synthesized from mixtures of melamine as nitrogen and carbon sources and calcium citrate as carbon source and porogen system. Considering the physicochemical and textural properties of the prepared carbons, a melamine/citrate ratio of 2:1 was selected to study the effect of the pyrolysis temperature. It was observed that a minimum pyrolysis temperature of 750 °C is required to obtain a carbonaceous structure. However, although there is a decrease in the nitrogen amount at higher pyrolysis temperatures, a gradual development of the porosity is produced from 750 °C to 850 °C. Above that temperature, a deterioration of the carbon porous structure is produced. All the prepared carbon materials, with no need for a further activation treatment, were active in the hydrogenation reaction of 1-chloro-4-nitrobenzene. A full degree of conversion was reached with the most active catalysts obtained from 2:1 melamine/citrate mixtures pyrolyzed at 850 °C and 900 °C, which exhibited a suitable compromise between the N-doping level and developed mesoporosity that facilitates the access of the reactants to the catalytic sites. What is more, all the materials showed 100% selectivity for the hydrogenation of the nitro group to form the corresponding chloro-aniline.

Hydrogen Spillover-Accelerated Selective Hydrogenation on WO3 with ppm-Level Pd

Hydrogen spillover from the metal to the support opens a fresh avenue to design dual-active site catalysts for selective hydrogenation. However, very limited knowledge has been obtained to reveal the relationship between the capacity of hydrogen spillover and catalytic performance of hydrogenation. Herein, hydrogen spillover-dependent selective hydrogenation has been demonstrated on WO₃-supported ppm-level Pd (PdHD/WO₃), where the *H species generated and spilled from Pd to WO₃ are readily utilized for addition of a reactant. The WO₃ supports with a hexagonal phase and a suitable oxygen defect concentration can enhance the capacity of hydrogen spillover, significantly accelerating the catalytic activity of PdHD/WO₃. For the hydrogenation of 4-chloronitrobenzene, the PdHD/WO₃ catalysts with the highest capacity of hydrogen spillover yielded a turnover frequency (TOF) of 47,488 h^-1 (33 times higher than that of traditional Pd/C). Meanwhile, benefiting from the hydrogen spillover, the unique adsorption of 4-chloronitrobenzene via the nitro group on the oxygen vacancy of WO₃ guaranteed >99.9% selectivity of 4-chloroaniline during the whole hydrogenation. This work thus helps to create an effective method for fabricating cost-effective nanocatalysts with an extremely low Pd loading for the ideal hydrogenation with extremely high activity and selectivity.

Fe3C nanoclusters integrated with Fe single-atom planted in nitrogen doped carbon derived from truncated hexahedron zeolitic imidazolate framework for the efficient transfer hydrogenation of halogenated nitrobenzenes

The control of morphology, structure and composition of metal-organic frameworks derived metal-nitrogen doped porous carbon (M-N-C) with high precision and accuracy is essential for the catalytic performance. While single-atom or small-sized nanometer catalysts show notable effects in catalysis, one catalyst combining the advantages of single-atom and nanometer catalysts may cultivate more benefits. Herein, we designed and successfully fabricated a series of Fe-doped ZIF-x with different morphologies (cube→truncated hexahedron→truncated octahedron) in one pot by simply adjusting the adding amount of vitamin C. After high-temperature calcination, Fe₃C integrated with Fe single-atom planted in N-doped carbon (Fe_SA/Fe_NC-N-C-x) with various morphology, structure and composition could be acquired. Among them, Fe_SA/Fe_NC-N-C-0.75 exhibited the best catalytic performance for the transfer hydrogenation of halogenated nitrobenzenes with N₂H₄·H₂O under room temperature. Acid-leaching tests, poisoning experiments, and the density functional theory calculations showed that Fe₃C integrated with Fe single-atom had a better catalytic effect than the separated Fe₃C or Fe single-atom.

Emerging Applications of Synchrotron Radiation X-Ray Techniques in Single Atomic Catalysts

Single atom catalysts (SACs) can achieve a maximum atom utilization efficiency of 100%, which provides significantly increased active sites compared with traditional catalysts during catalytic reactions. Synchrotron radiation technology is an important characterization method for identifying single-atom catalysts. Several types of internal information, such as the coordination number, bond length and electronic structure of metals, can all be analyzed. This review will focus on the introduction of synchrotron radiation techniques and their applications in SACs. First, the fundamentals of synchrotron radiation and the corresponding techniques applied in characterization of SACs will be briefly introduced, such as X-ray absorption near edge spectroscopy and extended X-ray absorption fine structure spectroscopy and in situ techniques. The detailed information obtained from synchrotron radiation X-ray characterization is described through four routes: 1) the local environment of a specific atom; 2) the oxidation state of SACs; 3) electronic structures at different orbitals; and 4) the in situ structure modification during catalytic reaction. In addition, a systematic summary of synchrotron radiation X-ray characterization on different types of SACs (noble metals and transition metals) will be discussed.

Recent Advances in Carbon-Based Iron Catalysts for Organic Synthesis

Carbon-based iron catalysts combining the advantages of iron and carbon material are efficient and sustainable catalysts for green organic synthesis. The present review summarizes the recent examples of carbon-based iron catalysts for organic reactions, including reduction, oxidation, tandem and other reactions. In addition, the introduction strategies of iron into carbon materials and the structure and activity relationship (SAR) between these catalysts and organic reactions are also highlighted. Moreover, the challenges and opportunities of organic synthesis over carbon-based iron catalysts have also been addressed. This review will stimulate more systematic and in-depth investigations on carbon-based iron catalysts for exploring sustainable organic chemistry.

Nanocarbon-based catalysts for selective nitroaromatic hydrogenation: A mini review

Selective hydrogenation of nitroaromatics to the corresponding anilines is a key topic for research in fine chemical industrial fields. Nanocarbon materials with good chemical stability, high electrical conductivity, and good mechanical performance have been regarded as promising candidates in the catalytic field, and have shown a wide range of applications in recent years. Controllable synthesis on the structure, morphology, and active sites of nanocarbon-based catalysts is vital to the development of highly efficient catalysts. In this mini-review, we summarize the recent progresses of nanocarbon materials by focusing on the synthesis approaches and their corresponding nanostructures, including carbon nanofibers, carbon nanotubes, graphene, porous carbon, carbon spheres, and metal organic framework-derived carbon materials. The design and catalytic performance of these nanocarbon materials have been systematically discussed. Finally, the emerging challenges and future prospective for developing advanced nanocarbon-based catalysts are outlined.

A Reusable FeCl3∙6H2O/Cationic 2,2′-Bipyridyl Catalytic System for Reduction of Nitroarenes in Water

The association of a commercially-available iron (III) chloride hexahydrate (FeCl3∙6H2O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under air using 1–2 mol% of catalyst in the presence of nitroarenes and 4 equiv of hydrazine monohydrate (H2NNH2∙H2O) in neat water at 100 °C for 12 h, and provided high to excellent yields of aniline derivatives. After separation of the aqueous catalytic system from the organic product, the residual aqueous solution could be applied for subsequent reuse, without any catalyst retreatment or regeneration, for several runs with only a slight decrease in activity, proving this process eco-friendly.

Atomically Dispersed Fe-N5 Sites Anchored on 3D N-Doped Porous Carbon for Efficient Selective Oxidation of Aromatic Alkanes at Room Temperature

On account of the increasing demand for aromatic ketones and the challenging task of mass production in the chemical industry, efficient and sustainable catalysts are urgently needed to catalyze the conversion of aromatic alkyl compounds into high value-added products via the activation of C-H bonds. Herein, Fe single-site atoms anchored on a N-doped three-dimensional (3D) porous carbon nanostructure (Fe-MEG-800) synthesized through the self-assembly hydrothermal method are reported. Detailed characterization analyses, such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), are employed to prove the isolated single Fe atom dispersing on the carbon nanostructure, along with X-ray absorption spectroscopy (XAS) and Mössbauer spectroscopy analysis confirming the Fe-N₅ coordination structure. Furthermore, the 3D cross-linked structure not only provides an abundant open-framework structure for the mass transfer during the reaction but also facilitates the exposure of more active sites and promotes the reaction procedure. The as-prepared catalyst possesses high catalytic activity toward the C-H bond at room temperature. In the model reaction of oxidizing ethylbenzene (EB) to high-value acetophenone (AcPO), the conversion and the selectivity of the reaction are both over 99%. In addition, the catalyst also presents favorable stability with retaining high performance even after eight cycles. The possible adsorption sites of the reactant and oxidant are explored through density functional theory (DFT) calculations. Based on the analysis of experimental and theoretical results, a possible mechanism for the oxidation of EB to AcPO involving •OH, O₂^•-, and ¹O₂ is also proposed.

Homogeneity of Supported Single-Atom Active Sites Boosting the Selective Catalytic Transformations

Selective conversion of specific functional groups to desired products is highly important but still challenging in industrial catalytic processes. The adsorption state of surface species is the key factor in modulating the conversion of functional groups, which is correspondingly determined by the uniformity of active sites. However, the non-identical number of metal atoms, geometric shape, and morphology of conventional nanometer-sized metal particles/clusters normally lead to the non-uniform active sites with diverse geometric configurations and local coordination environments, which causes the distinct adsorption states of surface species. Hence, it is highly desired to modulate the homogeneity of the active sites so that the catalytic transformations can be better confined to the desired direction. In this review, the construction strategies and characterization techniques of the uniform active sites that are atomically dispersed on various supports are examined. In particular, their unique behavior in boosting the catalytic performance in various chemical transformations is discussed, including selective hydrogenation, selective oxidation, Suzuki coupling, and other catalytic reactions. In addition, the dynamic evolution of the active sites under reaction conditions and the industrial utilization of the single-atom catalysts are highlighted. Finally, the current challenges and frontiers are identified, and the perspectives on this flourishing field is provided.

Reversing the Catalytic Selectivity of Single-Atom Ru via Support Amorphization

Supported single-atom catalysts (SACs), with the extremely homogenized active sites could achieve high hydrogenation selectivity toward one of the functional groups coexisting in the reactant molecule. However, as to the target group, the control of selective recognition and activation by SACs still remains a challenge. Herein, the phase engineering of the support is adopted to control the chemo-recognition behavior of SACs in selective hydrogenation. Single-atom Ru on amorphous porous ultrathin TiO₂ nanosheets (Ru₁/a-TiO₂) is constructed, in which Ru is more positively charged than that in the crystalline counterpart (Ru₁/c-TiO₂). Moreover, in the nitro/vinyl selective hydrogenation process, Ru₁/a-TiO₂ shows superior nitro selectivity, opposite to the vinyl selectivity of Ru₁/c-TiO₂. Density functional theory calculations for single-atom Ru of different charge states show that the reactant adsorption configuration could be inverted in the amorphous TiO₂, accounting for the chemo-recognition behavior controlled by the phase of support.

Cobalt nanoparticles supported on microporous nitrogen-doped carbon for efficient catalytic transfer hydrogenation reaction between nitroarenes and N-heterocycles

Catalytic transfer hydrogenation reaction between nitroarenes and saturated N-heterocycles to simultaneously synthesize value-added anilines and unsaturated N-heterocycles is attractive due to its low-cost, atomic economic, and environmental-friendly properties. Herein, we...

Single-Atom (Iron-Based) Catalysts: Synthesis and Applications

Supported single-metal atom catalysts (SACs) are constituted of isolated active metal centers, which are heterogenized on inert supports such as graphene, porous carbon, and metal oxides. Their thermal stability, electronic properties, and catalytic activities can be controlled via interactions between the single-metal atom center and neighboring heteroatoms such as nitrogen, oxygen, and sulfur. Due to the atomic dispersion of the active catalytic centers, the amount of metal required for catalysis can be decreased, thus offering new possibilities to control the selectivity of a given transformation as well as to improve catalyst turnover frequencies and turnover numbers. This review aims to comprehensively summarize the synthesis of Fe-SACs with a focus on anchoring single atoms (SA) on carbon/graphene supports. The characterization of these advanced materials using various spectroscopic techniques and their applications in diverse research areas are described. When applicable, mechanistic investigations conducted to understand the specific behavior of Fe-SACs-based catalysts are highlighted, including the use of theoretical models.

Bimetallic Au-Pd nanoparticles supported on silica with a tunable core@shell structure: enhanced catalytic activity of Pd(core)-Au(shell) over Au(core)-Pd(shell)

A facile ligand-assisted approach of synthesizing bimetallic Au-Pd nanoparticles supported on silica with a tunable core@shell structure is presented. Maneuvering the addition sequence of metal salts, both Aucore-Pdshell (Au@Pd-SiO2) and Pdcore-Aushell (Pd@Au-SiO2) nanoparticles were synthesized. The structures and compositions of the core-shell materials were confirmed by probe-corrected HRTEM, TEM-EDX mapping, EDS line scanning, XPS, PXRD, BET, FE-SEM-EDX and ICP analysis. The synergistic potentials of the core-shell materials were evaluated for two important reactions viz. hydrogenation of nitroarenes to anilines and hydration of nitriles to amides. In fact, in both the reactions, the Au-Pd materials exhibited superior performance over monometallic Au or Pd counterparts. Notably, among the two bimetallic materials, the one with Pdcore-Aushell structure displayed superior activity over the Aucore-Pdshell structure which could be attributed to the higher stability and uniform Au-Pd bimetallic interfaces in the former compared to the latter. Apart from enhanced synergism, high chemoselectivity in hydrogenation, wide functional group tolerance, high recyclability, etc. are other advantages of our system. A kinetic study has also been performed for the nitrile hydration reaction which demonstrates first order kinetics. Evaluation of rate constants along with a brief investigation on the Hammett parameters has also been presented.

Pd Anchored on a Phytic Acid/Thiourea Polymer as a Highly Active and Stable Catalyst for the Reduction of Nitroarene

A kind of N, P, C, O-containing polymer was easily prepared via microwave heating of phytic acid and thiourea just for 90 s. After impregnation and reduction of H₂PdCl₄, highly dispersed Pd single atoms/sub-nano clusters loaded on the phytic acid/thiourea polymer (Pd-CNSP) were successfully obtained. Owing to the synergetic effect of the polymer support and Pd, the catalyst Pd-CNSP achieves a great atomic efficiency of Pd species and exhibits an outstanding catalytic ability in the reduction of 4-nitrophenol. The k value of the catalyst Pd-CNSP (2.17 min^-1 mg^-1) is about 19 times higher than that of the commercial Pd/C (5 wt %) catalyst. The turnover frequency value is as high as 848 min^-1, which is the highest value reported so far. Pd-CNSP also has good selectivity for the reduction of halogen-substituted (Cl and Br) nitroaromatics. It is expected to be mass-produced and used in other industrial hydrogenation reactions.

Catalytic Nanomaterials toward Atomic Levels for Biomedical Applications: From Metal Clusters to Single-Atom Catalysts

Single-atom catalysts (SACs) featuring the complete atomic utilization of metal, high-efficient catalytic activity, superior selectivity, and excellent stability have been emerged as a frontier in the catalytic field. Recently, increasing interests have been drawn to apply SACs in biomedical fields for enzyme-mimic catalysis and disease therapy. To fulfill the demand of precision and personalized medicine, precisely engineering the structure and active site toward atomic levels is a trend for nanomedicines, promoting the evolution of metal-based biomedical nanomaterials, particularly biocatalytic nanomaterials, from nanoparticles to clusters and now to SACs. This review outlines the syntheses, characterizations, and catalytic mechanisms of metal clusters and SACs, with a focus on their biomedical applications including biosensing, antibacterial therapy, and cancer therapy, as well as an emphasis on their in vivo biological safeties. Challenges and future perspectives are ultimately prospected for SACs in diverse biomedical applications.

Graphene-supported single-atom catalysts and applications in electrocatalysis

Supported metal nanostructures are the most extensively studied heterogeneous catalysts, benefiting from easy separation, regeneration and affordable cost. The size of the supported metal species is one of the decisive factors in determining the activity of heterogeneous catalysts. Particularly, the unsaturated coordination environment of metal atoms preferably act as the active centers, minimizing these metal species can significantly boost the specific activity of every single metal atom. Single-atom catalysts/catalysis (SACs), containing isolated metals atomically dispersed on or coordinated with the surface of a support material, represent the ultimate utilization of supported metals and maximize metal usage efficiency. Graphene, a two-dimensional star material, exhibiting extraordinary physical and chemical properties, has been approved as an excellent platform for constructing SACs. When atomically dispersed metal atoms are strongly anchored on the graphene surface, featuring ultra-high surface area and excellent electronic properties, SACs offer a great potential to significantly innovate the conventional heterogeneous catalysis, especially in the field of electrocatalysis. In this review, a detailed discussion of graphene-supported SACs, including preparation approaches, characterization techniques and applications on typical electrocatalytic reactions is provided. The advantages and unique features of graphene-supported SACs as efficient electrocatalysts and the upcoming challenges for improving their performance and further practical applications are also highlighted.

Single-Atom Catalysts across the Periodic Table

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Fe Single Atoms and Fe2O3 Clusters Liberated from N-Doped Polyhedral Carbon for Chemoselective Hydrogenation under Mild Conditions

In the area of catalysis, selective reduction of nitro compounds to amino compounds is a colossal challenge due to the existence of competitive reducible functional groups. Herein, an Fe-based catalyst Fe_SAs/Fe₂O_3ACs/N-doped polyhedral carbon (NPC) has been designed and synthesized. As we expected, compared with Fe_SAs and Fe_NPs, Fe_SAs/Fe₂O_3ACs/NPC shows excellent catalytic performance (turnover frequency up to 1923 h^-1, calculated with nitrobenzene), chemoselectivity, and tolerance during the hydrogenation reaction of nitro compounds under room temperature because of the synergistic effects between Fe_SAs and Fe₂O_3ACs. The theoretical calculations show that Fe_SAs prefers to undergo hydrazine decomposition to generate hydrogen and the Fe₂O_3ACs surface is more active toward the nitrobenzene reduction to aniline.

Dopamine polymer derived isolated single-atom site metals/N-doped porous carbon for benzene oxidation

Isolated single-atom site metals/nitrogen-doped porous carbon (ISAS M/NPC, M = Fe, Co, Ni) catalysts are successfully prepared by a top-down polymerization-pyrolysis-etching-activation (PPEA) strategy, which uses dopamine as the precursor. Due to the isolated single atom Fe active sites and porous structure, the ISAS Fe/NPC catalyst displays a high benzene conversion up to 42.6% and nearly 100% phenol selectivity.

Effect of Fe, Co and Ni promoters on MoS2 based catalysts for chemoselective hydrogenation of nitroarenes

The effect of Fe, Co and Ni promoters on supported MoS2 catalysts for hydrogenation of nitroarenes were systematically investigated via experiment, characterization and DFT calculation. It was found that the addition of promoters remarkably improved the reaction activity in a sequence of Ni > Co > Fe > Mo. Meanwhile Ni promoted catalyst with the best performance showed good recyclability and chemoselectivity for a wide substrate scope. The characterization results revealed that the addition of promoters decreased the interaction between Mo and support and facilitated the reductive sulfidation of Mo species to produce more coordinated unsaturated sites (CUS). DFT calculations showed that the addition of promoters increased the formation of CUS, and enhanced the adsorption of hydrogen. The influence degree of promoters followed the sequence Ni > Co > Fe > Mo, which was consistent with those of the activities. Nitrobenzene hydrogenation and hydrogen activation occurred at the S and Mo edge, respectively. The adsorbed hydrogen diffused from the Mo edge to the S edge to participate in the hydrogenation reaction. Mechanism investigation showed that the main reason for increased activity by the addition of promoters was the increase of amounts of CUS and the secondary reason was the augmentation of intrinsic activity of CUS. The present studies give a new understanding for promoter modified MoS2 catalysts applied for hydrogenation of nitroarenes.

Atomic site electrocatalysts for water splitting, oxygen reduction and selective oxidation

This review summarized the fabrication routes and characterization methods of atomic site electrocatalysts (ASCs) followed by their applications for water splitting, oxygen reduction and selective oxidation.