Hydrogenation Research Articles

Catalytic Hydrogenation of CO2 by Direct Air Capture to Valuable C1 Products Using Homogenous Catalysts.

Growing atmospheric CO2 concentrations are a global concern and a primary factor contributing to global warming. Development of integrated CO2 capture and conversion protocols is necessary to mitigate this alarming challenge. Though CO2 hydrogenation to produce formic acid and methanol has seen many strides in the past decades, most studies utilize pure CO2 for this transformation. The CO2 concentration in the atmosphere stands at 400 ppm and reports that utilize direct air capture as the strategy to capture CO2 and utilize it for production of formic acid and methanol have only been reported in the past few years. This perspective summarizes such reports with a focus on the CO2-capturing additive, reaction solvent, and the molecular catalyst used to affect the transformation.

Photoelectrochemical and Catalytic Hydrogen Generation from Hydrolysis of NaBH4 using Ruthenium and Platinum Decorated ZnO/TiO2 Heterojunction Thin Film Electrodes

Photoelectrochemical and Catalytic Hydrogen Generation from Hydrolysis of NaBH4 using Ruthenium and Platinum Decorated ZnO/TiO2 Heterojunction Thin Film Electrodes

Operando Unveiling of Hydrogen Spillover Mechanisms on Tungsten Oxide Surfaces.

Hydrogen spillover is an important process in catalytic hydrogenation reactions, facilitating H2 activation and modulating surface chemistry of reducible oxide catalysts. This study focuses on the operando unveiling of platinum-induced hydrogen spillover on monoclinic tungsten trioxide (γ-WO3), employing ambient pressure X-ray photoelectron spectroscopy, density functional theory calculations and microkinetic modeling to investigate the dynamic evolution of surface states at varied temperatures. At room temperature, hydrogen spillover results in the formation of W5+ and hydrogen intermediates (hydroxyl species and adsorbed water), facilitated by Pt metal clusters. With increasing temperature, water desorption, reverse hydrogen spillover and surface-to-bulk diffusion of hydrogen atoms compete with each other, leading initially to reoxidation and then further reduction of W atoms in the near-surface. The combined experimental results and simulations provide a comprehensive understanding of the mechanisms underlying hydrogen interaction with reducible metal oxides, lending insights of relevance to the design of enhanced hydrogenation catalysts.

Ultrasonically Activated Liquid Metal Catalysts in Water for Enhanced Hydrogenation Efficiency.

Hydride (H-) species on oxides have been extensively studied over the past few decades because of their critical role in various catalytic processes. Their syntheses require high temperatures and the presence of hydrogen, which involves complex equipment, high energy costs, and strict safety protocols. Hydride species tend to decompose in the presence of atmospheric oxygen and water, which reduces their catalytic activities. These challenges highlight the need for further research to improve the stability and efficiency of catalytic processes and develop safer and cost-effective synthesis methods. This paper introduces an ultrasonic fabrication method for gallium hydride species on liquid metal (LM) nanoparticles (Ga-H@LM NPs) in water and describes the evaluation of their catalytic properties. The Ga-H@LM NPs were synthesized by dispersing liquid metals of eutectic gallium-indium in water using a two-step ultrasonication process in an ice bath. The presence of Ga-H species was confirmed by Fourier-transform infrared spectroscopy. The Ga-H@LM NPs demonstrated the rapid catalytic hydrogenation of 4-nitrophenol and reductive degradation of azo dyes within minutes without the need for external reducing agents like NaBH4. The proposed mechanism involves high-energy ultrasonic cavitation at the interface between LM NPs and water, which promotes the formation of H2 from water and its activation to form Ga-H on particles surface during ultrasonication. This study has significant implications for advancing the field of catalysis because it provides a novel and efficient catalytic method for the synthesis of stable hydride species on gallium oxides.

Lignin-Based Nanoparticles Stabilized Pickering Emulsion for Enhanced Catalytic Hydrogenation.

The development of green and easily regulated amphiphilic particles is crucial for advancing Pickering emulsion catalysis. In this study, lignin particles modified via sulfobutylation were employed as solid emulsifiers to support Pd nanoparticles (NPs), thereby enhancing the catalytic efficiency of biphasic reactions. Sulfobutylation of lignin effectively adjusted the hydrophilic-hydrophobic balance, resulting in controlled emulsion types and droplet sizes. Pd NPs were loaded onto lignin with a 50% sulfobutylation ratio through the in situ reduction of active functional groups, further stabilized by the cross-linked network structure of lignin. In the hydrogenation of nitrobenzene, the Lig-50S-0.6Pd catalyst exhibited superior activity compared to traditional Pd/C catalysts, which is attributed to the high retention of active sites and increased interfacial area. This work underscores the potential for designing lignin-based amphiphilic particles and developing Pickering emulsion-enhanced reactions.

B, N Codoped Defective Reduced Graphene Oxide as a Highly Efficient Frustrated Lewis Pairs Catalyst for the Selective Hydrogenation of α,β-Unsaturated Aldehydes to Unsaturated Alcohols.

The development of all-solid-state frustrated Lewis pairs (FLPs) metal-free hydrogenation catalysts with excellent activity and stability remains a significant challenge. In this work, B, N codoped FLPs catalysts (De-rGO-NxBy) were prepared by the strategy of fabricating carbon defects and heteroatom doping on the surface of reduced graphene oxide and applied in the selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols. It was found that electron-rich pyridine-N (Lewis base) and adjacent electron-deficient B-N (Lewis acid) sites could be constructed on the surface of reduced graphene oxide using dicyandiamide and metaboric acid as N and B sources, thus forming FLPs sites. More importantly, the constructed carbon defects could facilitate the formation of pyridinic-N/B-N FLPs sites, thereby improving the catalytic hydrogenation activity and the selectivity to unsaturated alcohols. Furthermore, in situ DRIFTS and DFT calculations show that the pyridinic-N/B-N FLPs sites can efficiently activate the C═O of aldehydes and H2 molecules with only 0.53 eV dissociation energy of the H-H bond. Also, the catalyst presents excellent catalytic performance in the transfer hydrogenation reactions with cyclohexanol and its derivatives as hydrogen sources. This study provides new ideas for the design and preparation of all-solid-state FLPs metal-free catalysts and promotes the green synthesis of unsaturated alcohols.

Tuning Fork Scanning Electrochemical Cell Microscopy for Resolving Morphological and Redox Properties of Single Ag Nanowires.

We report a Tuning Fork Scanning Electrochemical Cell Microscopy (TF-SECCM) technique for providing morphological and electrochemical information on single redox-active entities. This new operation configuration of SECCM utilizes an electrolyte-filled nanopipette tip mounted onto a tuning fork force sensor to obtain a precise tip-sample distance control and surface morphological mapping capabilities. Redox activities of regions of interest (ROIs) can be investigated by scanning electrode potential by moving the nanopipette to any target regions while maintaining the constant force engagement of the tip with the sample. Using silver nanowires (Ag NWs) as a model system due to their extensive utilization in energy and sensing devices, TF-SECCM provides not only the topography of single Ag NWs but also their distinctive redox activities, catalytic hydrogen evolution reaction (HER) activities, and electrolyte anion adsorption/desorption features in contrast to NW bundles and a supporting substrate.

Research on the Performance Optimization of Molybdenum Disulfide for Multifunctional Applications

Molybdenum disulfide (MoS2), as a typical transition metal chalcogenide compound, has emerged as a research hotspot in nanomaterials due to its excellent electrochemical properties and catalytic activity. However, conventional MoS2 exhibits certain limitations in terms of its catalytic performance, electrical conductivity, and cycling stability. To address these issues, this paper aims to explore the improvement of the multifunctional performance of MoS2 via different performance optimisation strategies, such as heteroatom doping, semiconductor composites, as well as metallic and non-metallic loading. By reviewing and analyzing the relevant literature on the performance enhancement of MoS2 in recent years, this paper summarizes the specific applications and effects of these optimization strategies, highlighting that they significantly improve the performance of MoS2 in fields such as optics, electrochemical catalysis, lithium batteries, and supercapacitors, particularly in terms of catalytic activity, electrical conductivity, and cycling stability. The results indicate that the optimisation of MoS2 performance provides an important theoretical basis and practical guidance for its application in energy storage and catalytic hydrogen evolution.

Comparative study of the reaction characteristics and kinetics of catalytic hydrogenation involving propylene, 1-butene, and their mixture over Pt/ZrO2

Comparative study of the reaction characteristics and kinetics of catalytic hydrogenation involving propylene, 1-butene, and their mixture over Pt/ZrO2

Weakly Coordinating Anionic Microporous Polymer Networks as Scaffold for Molecular Gas Phase Hydrogenation Catalysis

Anionic microporous polymer networks are prepared from a fluorinated tetraarylborate precursor via the Yamamoto reaction. The charge density can be continuously varied by adjusting the ratio of a neutral tetraphenylmethane comonomer. The obtained polymer networks are stable under ambient conditions and exhibit a surface area of up to 1500 m2 g‐1. Cationic molecular complexes can be embedded in the anionic network by simple ion exchange, making them viable for gas phase catalytic reactions. In this case, the cationic complex of the Crabtree’s catalyst is introduced to prepare a solid material for the gas phase hydrogenation of ethylene to ethane at room temperature.

Tropos Diphenylmethane-Based Phosphine-Phosphoramidite Ligands: Design, Synthesis, and Application in Catalytic Asymmetric Hydrogenation.

A series of chiral hybrid diphosphorus ligands incorporating a conformationally flexible tropos diphenylmethane-based phosphoramidite unit have been developed and evaluated in the Rh-catalyzed asymmetric hydrogenation of 2-(1-arylvinyl)anilides and α-enamides, leading to up to >99% yield and 99% enantiomeric excess. Preliminary results from comparative studies showcased the extraordinary catalytic performance of these chiral tropos phosphine-phosphoramidite ligands, with a competency essentially superior to those of well-established ligands with a regular rigid backbone.

Entropy engineering activation of UiO-66 for boosting catalytic transfer hydrogenation

High-entropy metal-organic frameworks (HE-MOFs) hold promise as versatile materials, yet current rare examples are confined to low-valence elements in the fourth period, constraining their design and optimization for diverse applications. Here, a novel high-entropy, defect-rich and small-sized (32 nm) UiO-66 (ZrHfCeSnTi HE-UiO-66) has been synthesized for the first time, leveraging increased configurational entropy to achieve high tolerance to doping with diverse metal ions. The lattice distortion of HE-UiO-66 induces high exposure of metal nodes to create coordination unsaturated metal sites with a concentration of 322.4 μmol/g, which increases the abundance of Lewis acid-base sites, thereby achieving a significant improvement in the performance of the catalytic transfer hydrogenation (CTH) reaction. Systematic investigation manifests that the special electronic structure of HE-UiO-66 enhances the interaction and bonding with substrate molecules and reduces the energy barrier of the hydrogen transfer process. Our approach offers a new strategy for constructing coordination unsaturated metal sites in MOFs.

InNi alloy-induced interface effect promoting the parallel electron transfer: improved photothermal catalytic CO2 hydrogenation

InNi alloy-induced interface effect promoting the parallel electron transfer: improved photothermal catalytic CO2 hydrogenation

Site-Selective Copper(I)-Catalyzed Hydrogenation of Amides.

We present a bifunctional catalyst consisting of a copper(I)/N-heterocyclic carbene and an organocatalytic guanidine moiety that enables, for the first time, a copper(I)-catalyzed reduction of amides with H2 as the terminal reducing agent. The guanidine allows for reactivity tuning of the originally weakly nucleophilic copper(I) hydrides - formed in situ - to be able to react with difficult-to-reduce amides. Additionally, the guanidine moiety is key for the selective recognition of "privileged" amides based on simple and readily available heterocycles in the presence of other amides within one molecule, giving rise to hitherto unknown site-selective catalytic amide hydrogenation. A substrate scope, mechanistic investigations, and a working hypothesis supported by computational analysis for site-selectivity are presented.

Catalytic Deconstruction of Commercial and End-Of-Life Polyurethane with Heterogeneous Hydrogenation Catalyst.

Polyurethane (PU), as a thermoset polymer, is extensively utilized in various applications, such as refrigerator foams, sponges, elastomers, shoes, etc. However, the recycling of post-consumed PU poses significant challenges due to its intricate and extensive crosslinking structures. Catalytic hydrogenation is one of the most effective methods for recycling PU waste, nevertheless, there is currently a lack for a hydrogenation catalyst that is both high-performing, recyclable, and cost-effective for breaking down post-consumed PU materials. In this work, model PU and commercial PU were efficiently hydrodegraded into aromatic amines and polyol fractions by using a commercial NiMo/Al2O3 catalyst. Notably, the results indicated that PU waste can be efficiently degraded at a pressure of 5 MPa and at a temperature of 185 °C and yielding a significant amount of a valuable chemical monomers. With the assistance of hydrogenation catalyst, the C-N and C-O bonds with low energy barriers inside the polymer are cracked and the polymer hydrogenation process becomes feasible. This study demonstrates the capability of fluidized bed hydrogenation process, employing recyclable heterogeneous catalysts for the recycling of PU waste.

Enhanced catalytic transfer hydrogenation of p-nitrophenol using formaldehyde: MnO2-supported Ag nanohybrids with tuned d-band structure.

The catalytic reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) is important in fine chemical synthesis, especially in the pharmaceutical, dye, and agrochemical industries. Sustainable methods are increasingly prioritized in these fields. Catalytic transfer hydrogenation (CTH) using formaldehyde (HCHO) as a hydrogen donor presents a safer and more environmentally friendly alternative due to its low-toxicity by-products and ease of handling. In this study, we developed manganese dioxide (MnO2)-supported silver (Ag) nanoparticles (NPs) as an efficient catalyst for the CTH of 4-NP using HCHO. The MnO2 support prevents the agglomeration of Ag NPs and acts as an electron-acceptor matrix, enhancing the adsorption and activation of HCHO and facilitating the formation of active hydrogen (H*). Structural characterization and density functional theory (DFT) simulations confirmed electron transfer from Ag to MnO2 in the Ag/MnO2 nanohybrids, driven by their distinct work functions. This electron transfer results in a depletion of electrons in the Ag 4d orbitals, shifting its valence configuration from 4d10 to 4d10-x, creating electron-deficient Ag sites that promote HCHO activation, thereby improving the CTH process. The optimized 15% Ag/MnO2 catalyst demonstrated enhanced catalytic hydrogenation of 4-NP with HCHO, achieving a turnover frequency of 3.83min-1. This study highlights the potential of Ag-based nanohybrids in improving catalytic performance for HCHO-assisted CTH by tuning the d-band structure with suitable oxide supports.

Highly selective catalytic hydrogenation of furfural and acetophenone on S-doped mesoporous carbon Sphere-Supported Pd nanocluster catalyst

The efficient catalytic conversion of the biomass platform molecule furfural into biofuels or other high-value-added chemicals is currently a research hotspot. However, the hydrogenation of furfural possesses challenges due to the occurrence of multiple side reactions that generate various by-products. Herein, S-doped mesoporous carbon spheres (CS-S) with an ordered and accessible structure were precisely designed and synthesized. Subsequently, ∼1.8 nm Pd nanoclusters were immobilized within the radial mesoporous structure of CS-S to obtain a Pd/CS-S catalyst. This catalyst was used for the hydrogenation of furfural and acetophenone into tetrahydrofurfuryl alcohol (THFA) and 1-phenylethanol, respectively, and 99 % conversion and more than 90 % selectivity were achieved. Mechanistic study revealed that the electron-deficient Pd nanoclusters anchored on CS-S exhibit higher adsorption energies for reactant molecules, thus facilitating the pre-adsorption and activation of substrate molecules. Moreover, the Gibbs free energy for each step of the hydrogenation process is lower on the electron-deficient Pd metal surface, leading to excellent catalytic hydrogenation performance. In addition, the Pd/CS-S catalyst also exhibited remarkable recyclability and stability over multiple reaction cycles. This work facilitates the construction of stable metal nanocluster-based catalysts for enabling highly selective catalytic hydrogenation.

Recovery of palladium from solution by defective Carbon nitride and Regenerating as a hydrogenation catalysis

Recovery of palladium from solution by defective Carbon nitride and Regenerating as a hydrogenation catalysis

Regioselective intermolecular carboamination of allylamines via nucleopalladation: empowering three-component synthesis of vicinal diamines.

An intermolecular carboamination reaction of allyl amines under Pd(ii)-catalysis is reported, expediting the synthesis of valuable vicinal diamines embedded in a functionally enriched linear carbon framework with high yields and exclusive Markovnikov selectivity. Central to our approach is the strategic use of a removable picolinamide auxiliary, which directs the regioselectivity during aminopalladation and stabilizes the crucial 5,5-palladacycle intermediate. This stabilization facilitates oxidative addition to carbon electrophiles, enabling the simultaneous incorporation of diverse aryl/styryl groups as well as important amine motifs, such as sulfoximines and anilines, across carbon-carbon double bonds. The protocol features broad substrate compatibility, tolerance to various functional groups, and scalability. The utility of this method is further demonstrated by the site-selective diversification of pharmaceutical agents. Additionally, these products serve as versatile intermediates for synthesizing heterocycles and function as effective ligands in catalytic transfer hydrogenation reactions. Notably, this work represents a rare instance of nucleopalladation-guided intermolecular carboamination of allylamines.

Recent advances in the enantioselective synthesis of chiral sulfones via asymmetric hydrogenation.

Chiral sulfones are key structural motifs that extensively exist in natural products, drugs, and biologically active compounds. During the past few decades, rapid development has been made with respect to the highly enantioselective synthesis of chiral sulfones, in which the catalytic asymmetric hydrogenation of unsaturated sulfones provides an efficient and powerful methodology to construct chiral sulfones and their derivatives. This review highlights the progress achieved in transition metal (ruthenium, rhodium, iridium, and nickel) catalyzed direct asymmetric hydrogenation of a variety of unsaturated sulfones from the aspects of the substrate scope, catalytic mechanisms, and applications in the synthesis of biologically active molecules.