Chemoselective Hydrogenation Reactions Research Articles

Copper‐based nanocatalysts toward chemoselective hydrogenation reaction

AbstractCu‐based catalysts are widely used in various heterogeneous catalytic reaction systems, the precise control of their electronic structure is an intrinsic requirement for the rational design of metal catalysts, and it is also an important basis for clarifying their structure‐activity relationships. Changing the electronic structure of Cu‐based catalysts is an important way to improve the catalytic hydrogenation performance of Cu‐based catalysts by controlling the adsorption intensity between the reaction adsorbate and the active center. In this paper, the application of selective hydrogenation of Cu‐based catalysts is reviewed, with a special emphasis on the selective catalytic hydrogenation reduction of p‐nitrostyrene and CO2. This review particularly emphasizes the application of Cu‐based catalysts in the field of selective hydrogenation and discusses the influence of their different properties on selective hydrogenation performance.

Screening support effect of Pt/MOx for selective hydrogenation of cinnamaldehyde

In supported metal catalysts, solid support material is of great importance for immobilizing and dispersing metal species, which can affect the catalytic performance of supported metal catalysts in terms of selectivity. Rational design of supported metal catalysts with tailored performance, in particular with controlled catalytic performance, is highly desired yet poses challenges in chemoselective hydrogenation reactions. Here, platinum nanoparticles (Pt NPs) supported on a series of commercial oxides were synthesized by a facile wet impregnation and thermal treatment under the air. The catalytic performance of as-prepared catalysts was evaluated in chemoselective hydrogenation of cinnamaldehyde. The varied product distribution demonstrates that supports affect markedly on selectivity. Fourier transform infrared spectra (FTIR) spectroscopy reveals that the high selectivity towards cinnamyl alcohol could be attributed to the preferential adsorption of aldehyde group. Meanwhile, the existence of Ptδ+ could enhance activity markedly by facilitating the spillover of activated H species.

Boosting the catalysis of gold supported on perovskites by strong metal-support interaction

Gold catalysts show excellent selectivity in chemoselective hydrogenation reactions. However, their reactivity and stability are relatively inferior to Pt-group metal catalysts due to the moderate hydrogen activation and carbonaceous deposits. Herein, we reported that the strong metal-support interaction (SMSI) between gold nanoparticles and perovskites can increase the catalytic performance of gold-based catalysts in 3-nitrostyrene chemoselective hydrogenation reaction. HAADF-STEM elemental mapping images and line scan profiles confirmed that the oxide support can partially cover the surface of gold NPs, increasing the interfacial area between gold NPs and perovskites support. H2-D2 exchange reaction, reaction kinetic analysis and density functional theory calculations revealed that the apparent activation energy of 3-NS chemoselective hydrogenation reaction over gold supported on perovskites with SMSI effect was significantly decreased by the more facile H2 dissociation, 3-NS and its’ intermediate activation at the increased interface. This discovery of SMSI effect in Au and perovskites offers new insights into tuning performance of gold-based catalysts via changing the types of metal ions in perovskites.

Sabatier Phenomenon in Hydrogenation Reactions Induced by Single-Atom Density.

The Sabatier principle is a fundamental concept in heterogeneous catalysis that provides guidance for designing optimal catalysts with the highest activities. For the first time, we here report a new Sabatier phenomenon in hydrogenation reactions induced by single-atom density at the atomic scale. We produce a series of Ir single-atom catalysts (SACs) with a predominantly Ir1-P4 coordination structure with densities ranging from 0.1 to 1.7 atoms/nm2 through a P-coordination strategy. When used as the catalysts for hydrogenation, a volcano-type relationship between Ir single-atom density and hydrogenation activity emerges, with a summit at a moderate density of 0.7 atoms/nm2. Mechanistic studies show that the balance between adsorption and desorption strength of the activated H* on Ir single atoms is found to be a key factor for the Sabatier phenomenon. The transferred Bader charge on these Ir SACs is proposed as a descriptor to interpret the structure-activity relationship. In addition, the maximum activity and selectivity can be simultaneously achieved in chemoselective hydrogenation reactions with the optimized catalyst due to the uniform geometric and electronic structures of single sites in SACs. The present study reveals the Sabatier principle as an insightful guidance for the rational design of more efficient and practicable SACs for hydrogenation reactions.

Transfer Hydrogenation in Mesoporous Palladium: Polar Hydrogen Engineering to Realize High Selectivity of Alkyne Semi‐Hydrogenation

AbstractSemi‐hydrogenation of alkynes to industrially important alkenes is earnestly desirable in the fine chemical industry but energetically unfavorable. Herein, it is reported that mesoporous palladium (meso‐Pd) catalyst changes the hydrogenation pathways in ethanol with ammonium borane as the hydrogen source, realizing the high catalytic selectivity of ≈99% in semi‐hydrogenation of alkynes. Mechanism studies reveal that the active polar hydrogen can be produced and reserved well in the electron‐rich mesoporous channels of meso‐Pd catalyst, resulting in a transfer hydrogenation pathway, which selectively semi‐hydrogenates alkynes into alkenes without over‐hydrogenating alkenes into alkanes. Moreover, it is demonstrated that the polar hydrogen engineering of meso‐Pd catalyst is highly efficient in various alkyne semi‐hydrogenation and chemoselective hydrogenation reactions. The results thus establish metal catalyst mesostructuring as an alternative route for engineering polar hydrogen in the transfer hydrogenation reactions, thus realizing the high catalytic selectivity in various selective catalysis.

Platinum clusters anchored on sulfur-doped ordered mesoporous carbon for chemoselective hydrogenation of halogenated nitroarenes

Chemoselective hydrogenation of unsaturated organic compounds is a significant research topic in the catalysis field. Herein, a sulfur-doped ordered mesoporous carbon (SMC) material was prepared to anchor ultrafine platinum (Pt) clusters for the chemoselective hydrogenation of halogenated nitroarenes. The confinement effect of the ordered pores and the strong metal-support interaction caused by Pt clusters and sulfur atoms, efficiently suppress the aggregation and regulate the electronic states of the ultrafine Pt clusters. Thus, the hydrogenation of parachloronitrobenzene (p-CNB) shows high selectivity catalyzed by the ultrafine Pt clusters with electron-rich states. Meanwhile, the catalytic performance of the hydrogenation reaction catalyzed by Pt/SMC is capable of being maintained after at least 5 cycles, and the catalytic universality can also be applied to different halogenated nitroarenes hydrogenation. Therefore, this study may promote the research into the construction of noble metal-based catalysts for chemoselective hydrogenation reactions in green and sustainable chemical processes.

Mechanism of Catalytic Transfer Hydrogenation for Furfural Using Single Ni Atom Catalysts Anchored to Nitrogen-Doped Graphene Sheets.

Catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes using single metal atom catalysts supported on nitrogen-incorporated graphene sheet (M-Nx-Gr) materials has attracted increasing attention recently, yet the reaction mechanism remains to be explored. Compared to the Ni-N4-Gr model in which the dissociation of isopropanol is highly unfavorable as a result of steric hindrance and inertness of the Ni-N4 site embedded in graphene, the Ni-N3 site in Ni-N3-Gr is more active and facilitates the formation of *H with isopropanol as the H donor, where the dissociation of H from isopropanol with an energy barrier of 0.83 eV is the rate-determining step. An alternative reaction path starts from the coadsorption of isopropanol and furfural molecules at the Ni-N3 site, followed by a direct hydrogen transfer between the two molecules; however, the rate-determining step has a much higher energy barrier of 1.32 eV. Our calculations suggest that the hydrogenation of the aldehyde group is kinetically more favorable than the C═C hydrogenation, revealing the high chemoselectivity of furfural to furfuryl alcohol. Our investigations reveal that the CTH mechanism using the Ni-N3-Gr catalyst is different from that on traditional metal oxides, where the former has only one single active site, while two active sites are required for the latter. The proposed reaction mechanism of CTH for furfural in this study should be helpful to guide the design of single metal atom catalysts with appropriate N coordination for application in chemoselective hydrogenation reactions.

Selective Hydrogenation Properties of Ni-Based Bimetallic Catalysts

Metallic Ni shows high activity for a variety of hydrogenation reactions due to its intrinsically high capability for H2 activation, but it suffers from low chemoselectivity for target products when two or more reactive functional groups are present on one molecule. Modification by other metals changes the geometric and electronic structures of the monometallic Ni catalyst, providing an opportunity to design Ni-based bimetallic catalysts with improved activity, chemoselectivity, and durability. In this review, the hydrogenation properties of these catalysts are described starting from the typical methods of preparing Ni-based bimetallic nanoparticles. In most cases, the reasons for the enhanced catalysis are discussed based on the geometric and electronic effects. This review provides new insights into the development of more efficient and well-structured non-noble metal-based bimetallic catalytic systems for chemoselective hydrogenation reactions.

Atomically Dispersed Cu Catalyst for Efficient Chemoselective Hydrogenation Reaction.

The Cu-based nanocatalysts have shown a high selectivity toward selective hydrogenation reaction, but the underlying catalytic mechanism is still murky. Herein, we report a new gram-scale strategy for realizing the single atom Cu site incorporated into the melem ring of graphitic carbon nitride (Cu1/CN) for understanding the catalytic mechanism of a hydrogenation reaction. The as-synthesized Cu1/CN exhibits unprecedented selectivity (100%), high activity (TOF = 2.9 × 103 h-1), and outstanding stability for selective hydrogenation of 4-nitrostyrene. We reveal that the presence of hydroxymethyl from trimethylolmelamine is beneficial to atomically disperse Cu atoms in the CN. X-ray absorption fine structure tests reveal that the Cu atom of Cu1/CN is dominated by the quaternary coordination way (Cu-N4) in the melem ring of CN. Density functional theory calculations confirm that the high reactivity and selectivity originate from the anchored Cu sites creating the optimal chemical environment for the highly efficient hydrogenation reaction.

Blocking the non-selective sites through surface plasmon-induced deposition of metal oxide on Au/TiO2 for CO-PROX reaction

CO preferential oxidation (PROX) in excess hydrogen is a promising strategy for CO removal in hydrogen-rich reformate. However, the CO conversion and CO 2 selectivity in the PROX reaction dramatically decrease with rising temperature, resulting in a major challenge to complete CO removal across a wide temperature window. Here, we developed a photoexcited deposition of metal oxide (PDMO) method based on surface plasmonic resonance of Au nanoparticles, which can tune the interfacial properties by depositing lead oxide at the Au-TiO 2 interface. The interface modified Pb 3 O 4 /Au/TiO 2 catalyst can successfully eliminate CO in a wide temperature range (70°C–140°C) and exhibit superior stability in the PROX reaction. Further experiments demonstrated that the improved PROX performance is due to the severely depressed hydrogen oxidation through simultaneously inhibiting the activation of hydrogen and oxygen. The results further reveal that the interface of Au/TiO 2 is the superactive but non-selective site for H 2 and CO oxidation. • Photoexcited deposition of metal oxide method is employed for interface engineering • Interface-engineered Au-TiO 2 helps to identify the active site in CO and H 2 oxidation • Blocking the non-selective sites greatly improves the CO-PROX performance • Interface anchoring with inert lead oxide enhances long-term thermal stability Against the background of the carbon-neutral era, the liquid sunshine industry is booming due to the consumption of greenhouse gas (CO 2 ) and the solution of storage and transportation of H 2 energy. However, before the terminal application of H 2 energy, CO must be removed in the H 2 -rich reformate to avoid poisoning the noble metal catalysts. Gold-catalyzed CO preferential oxidation (PROX) has great potential in the removal of CO from H 2 -rich reformate. The competition oxidation of CO and H 2 at the interface of gold support always results in a decrease in CO oxidation conversion and selectivity, especially at high temperature. However, it is a major challenge to distinguish the interfacial sites from the other parts of nanoparticle surface. We show here that the interface of Au-TiO 2 is modified by our photoexcited deposition of metal oxide (PDMO) method, which greatly affects the performance of the CO-PROX reaction. The interfacial area of metal support is the ultrahigh active site in catalysis. However, the ultrahigh active sites are normally adverse for chemoselective oxidation or hydrogenation reaction. Interface-engineered catalyst is prepared based on a selective photoexcited deposition of metal oxide method and shows greatly improved performance in CO preferential oxidation in H 2 -rich stream (PROX reaction).

Reaction kinetics and phase behavior in the chemoselective hydrogenation of 3-nitrostyrene over Co-N-C single-atom catalyst in compressed CO2

Single-atom catalysts (SACs) have demonstrated excellent performances in chemoselective hydrogenation reactions. However, the employment of precious metals and/or organic solvents compromises their sustainability. Herein, we for the first time report the chemoselective hydrogenation of 3-nitrostyrene over noble-metal-free Co-N-C SAC in green solvent — compressed CO2. An interesting inverted V-curve relation is observed between the catalytic activity and CO2 pressure, where the conversion of 3-nitrostyrene reaches the maximum of 100% at 5.0 MPa CO2 (total pressure of 8.1 MPa). Meanwhile, the selectivities to 3-vinylaniline at all pressures remain high (> 99%). Phase behavior studies reveal that, in sharp contrast with the single phase which is formed at total pressure above 10.8 MPa, bi-phase composed of CO2/H2 gas-rich phase and CO2-expanded substrate liquid phase forms at total pressure of 8.1 MPa, which dramatically changes the reaction kinetics of the catalytic system. The reaction order with respect to H2 pressure decreases from ~0.5 to zero at total pressure of 8.1 MPa, suggesting the dissolved CO2 in 3-nitrostyrene greatly promotes the dissolution of H2 in the substrate, which is responsible for the high catalytic activity at the peak of the inverted V-curve.

Strong metal-support interaction boosting the catalytic activity of Au/TiO2 in chemoselective hydrogenation

Gold catalysts have been reported as highly effective catalysts in various oxidation reactions. However, for chemoselective hydrogenation reactions, gold-based catalysts normally show much lower catalytic activity than platinum group metals, even though their selectivities are excellent. Here, we report that the chemoselective hydrogenation activity of 3-nitrostyrene to 3-vinylaniline over Au/TiO2 can be enhanced up to 3.3 times through the hydrogen reduction strategy. It is revealed that strong metal-support interaction, between gold nanoparticles (NPs) and TiO2 support, is introduced through hydrogen reduction, resulting in partial dispersion of reduced TiOx on the Au surface. The partially covered Au not only increases the perimeter of the interface between the gold NPs and the support, but also benefits H2 activation. Reaction kinetic analysis and H2-D2 exchange reaction show that H2 activation is the critical step in the hydrogenation of 3-nitrostyrene to 3-vinylaniline. Density functional theory calculations verify that hydrogen dissociation and hydrogen transfer are favored at the interface of gold NPs and TiO2 over the hydrogen-reduced Au/TiO2. This study provides insights for fabricating highly active gold-based catalysts for chemoselective hydrogenation reactions.

Cobalt nanoclusters coated with N-doped carbon for chemoselective nitroarene hydrogenation and tandem reactions in water

Subnanometric cobalt nanoclusters covered by N-doped carbon layers (Co@NC-800) catalyze the chemoselective reduction of nitroarenes and the one-pot synthesis of secondary aryl amines and isoindolinones in aquo media under mild reaction conditions.

Zeolitic Imidazolate Framework Cores Decorated with Pd Nanoparticles and Coated Further with Metal–Organic Framework Shells (ZIF-8@Pd@MOF-74) as Nanocatalysts for Chemoselective Hydrogenation Reactions

The selective hydrogenation of Ar–C═C in the presence of Ar–NO2 is a long-standing challenge because of the uncontrolled nonselective nature of hydrogenation. In this study, the core–shell nanocata...

Colloidal Palladium Nanoparticles for Selective Hydrogenation of Styrene Derivatives with Reactive Functional Groups.

This article presents the catalysis investigation of octanethiolate-capped palladium nanoparticles (C8 PdNP) and phenylethanethiolate-capped palladium nanoparticles (PhC2 PdNP) for chemoselective catalytic hydrogenation reactions of styrene derivatives in the presence of other reducible functionalities. The results show that the C8 PdNP is highly active under mild reaction conditions (room temperature and atmospheric pressure) and selective for hydrogenating monosubstituted alkene groups without reducing other reactive functional groups such as nitro, halo, carbonyls, and so forth. In comparison, the noncovalent interactions between surface phenyl ligands and aromatic substrates are found to hinder the hydrogenation activity of PhC2 PdNP.

Selective Hydrogenation over Supported Metal Catalysts: From Nanoparticles to Single Atoms.

Selective catalytic hydrogenation has wide applications in both petrochemical and fine chemical industries, however, it remains challenging when two or multiple functional groups coexist in the substrate. To tackle this challenge, the "active site isolation" strategy has been proved effective, and various approaches to the site isolation have been developed. In this review, we have summarized these approaches, including adsorption/grafting of N/S-containing organic molecules on the metal surface, partial covering of active metal surface by metal oxides either via doping or through strong metal-support interaction, confinement of active metal nanoparticles in micro- or mesopores of the supports, formation of bimetallic alloys or intermetallics or core@shell structures with a relatively inert metal (IB and IIB) or nonmetal element (B, C, S, etc.), and construction of single-atom catalysts on reducible oxides or inert metals. Both advantages and disadvantages of each approach toward the site isolation have been discussed for three types of chemoselective hydrogenation reactions, including alkynes/dienes to monoenes, α,β-unsaturated aldehydes/ketones to the unsaturated alcohols, and substituted nitroarenes to the corresponding anilines. The key factors affecting the catalytic activity/selectivity, in particular, the geometric and electronic structure of the active sites, are discussed with the aim to extract fundamental principles for the development of efficient and selective catalysts in hydrogenation as well as other transformations.

Sub-2 nm Ir Nanoclusters Immobilized on Mesoporous Nitrogen-Doped Carbons as Efficient Catalysts for Selective Hydrogenation

The development of high-performance heterogeneous catalysts for chemoselective hydrogenation reactions is particularly important for the industrial production of fine-chemical intermediates and bio...

Decoration of Pd Nanoparticles with N and S Doped Carbon Quantum Dots as a Robust Catalyst for the Chemoselective Hydrogenation Reaction

Achieving high selectivity is one of the major challenges for the noble metal catalysts. A strategy of decoration of Pd nanoparticles by N–S doped carbon quantum dots (N,S-CQDs) to regulate selectivity is proposed. Through adjusting the loading amounts of N,S-CQDs, high selectivity toward catalytic hydrogenation reactions can be obtained. N,S-CQDs facilely adhere to the Pd nanoparticle via surface reactions among C–S/C–N species of N,S-CQDs and C–O species of the carbon support under the catalysis of Pd particles. N loss was detected due to the transformation of some C–N species into nitrogen-containing soluble substances or gas. However, S-containing species, specially −SO2/SO3 species, are turned into C–S–C (thiophene-S), leading to a strong coordination between Pd and S. As a result, a N,S-CQDs-Pd interface is fabricated, in which electrons transfer from Pd to S species and the interface of Pd–S plays a major role in hydrogen spillover and generation of dissociated hydrogen with negative charge. Conseq...

Hydrogenation of Halogenated 2'-Hydroxychalcones by Mycelia of Marine-Derived Fungus Penicillium raistrickii.

This study describes the chemoselective hydrogenation reaction of halogenated 2'-hydroxychalcones by the marine-derived fungus Penicillium raistrickii CBMAI 931. Initially, 2'-hydroxychalcone was utilized as a model for the selection of the appropriate conditions to perform the biotransformation reactions. The best results were obtained using mycelia and filtered culture broth, and this condition was chosen for the biotransformation reaction of 2'-hydroxychalcones substituted with methoxy and halogen groups. Experiments performed with 2'-hydroxychalcones dissolved in 600μL-DMSO were more effective than those performed using 300μL-DMSO, once solubility of the compounds influenced conversion rate in the liquid medium. The halogenated 2'-hydroxy-dihydrochalcones were obtained in good conversions (78-99%) and moderate isolated yields (31-65%). All biotransformation reactions using the marine-derived fungus P. raistrickii CBMAI 931 showed regioselective and chemoselective control for the formation of 2'-hydroxy-dihydrochalcones.

Pt Nanoparticles Supported over Porous Porphyrin Nanospheres for Chemoselective Hydrogenation Reactions

AbstractOptimizing the chemoselectivity in a chemical reaction catalyzed by metallic nanoparticles (NPs) hosted over a solid support is a big challenge, especially in the context of the sustainability of the process. Here we showed that chemoselectivity in the hydrogenation of 4‐nitrostyrene can be tailored on Pt‐loaded porphyrin nanospheres through the functionalization with sulfonic acid groups at the catalyst surface. 4‐Nitrostyrene is transformed to 4‐aminostyrene over sulfonated Pt‐POP‐SO3H, with ∼77.8 % selectivity at conversion of ∼90 %, whereas the pristine catalyst selectively produced ∼80 % 4‐ethylnitrobenezene at almost complete conversion level. The reversal of the selectivity could be attributed to the effect of the introduction of sulfonic acid group over the supported Pt NPs. Presence of sulfonic acid groups in the functionalized Pt‐porphyrin material has been confirmed from XPS, FT‐IR and elemental analysis data. Moreover, these catalysts are recyclable, suggesting their durability and chemical‐stability for long‐term sustainable operations.