Catalytic Transfer Hydrogenation Research Articles

Bifunctional Acid‐Base Zirconium Phosphonate for Catalytic Transfer Hydrogenation of Levulinic Acid and Cascade Transformation of Furfural to Biofuel Molecules

AbstractThe production of biofuels, such as furfural ether and γ‐valerolactone (GVL) from biomass platform chemicals furfural (FFA) and Levulinic acid (LA) is of significant interest. In this study, a nanoporous inorganic‐organic Zr−phosphonate catalyst (ZrNPO3) was synthesized and employed in the selective production of GVL (98.2 %) via catalytic transfer hydrogenation of LA. The catalyst containing acid‐base sites was further used to produce biofuel molecules like GVL and furfuryl ether under a mild reaction condition via cascade furfural transformation. The GVL selectivity was further improved using phosphotungstic acid@ZrNPO3. The catalytic optimization studies were combined with poisoning studies and the detailed physicochemical characterization to acquire insight into the structure‐activity correlation and reaction mechanism. The synergistic presence of the Lewis acidity and basicity on the catalyst was responsible for its remarkable activity. Designing a single catalyst for the one‐pot tandem transformation of FFA to GVL would be highly motivating for catalysis researchers and industrialists.

Efficiently catalytic transfer hydrogenation and fast separation of unsaturated alkene compounds over Pd/UiO-66 under green conditions

Stable Pd nanoparticles (Pd NPs) have been uniformly dispersed and immobilized into the metal-organic framework of UiO-66, Pd/UiO-66, by a facile impregnation reduction method. Pd/UiO-66 retains the integrity of the UiO-66 crystal structure and incorporated with ultrasmall Pd NPs(1.70 ± 0.32 nm). Using ammonium formate(AF) as a H-donor and water as solvent under green condition, the optimized 1.16 wt% Pd/UiO-66 catalyst exhibits remarkable activity in the catalytic transfer hydrogenation(CTH) of α-methylstyrene(AMS) into cumin(achieving 99.6% conversion of AMS and almost full selectivity to cumin with an extremely high turnover frequency value 456.7 h−1 at 323.15 K). Pd/UiO-66 also show superior catalytic activity in CTH of unsaturated alkene compounds to saturated compounds with excellent stability and recyclability. Furthermore, the as-formed saturated alkanes can be fast and automatic separated easily from the aqueous catalytic media. This study supplies a general method for immobilizing ultrafine Pd nanoparticles into crystalline MOFs and a “green” path for hydrogenation of unsaturated alkene compounds.

Effects of Activated-carbon-supported Nickel on Catalytic Transfer Hydrogenation of Cellulose to Hydrocarbons in a Straight-chain Aliphatic Hydrocarbon Solvent

Effects of Activated-carbon-supported Nickel on Catalytic Transfer Hydrogenation of Cellulose to Hydrocarbons in a Straight-chain Aliphatic Hydrocarbon Solvent

Iridium(triNHC)-Catalyzed Transfer Hydrogenation of Glycerol Carbonate without Exogenous Reductants

The iridium(Ir) (triNHC = tri-N-heterocyclic carbene)-catalyzed transfer hydrogenation of glycerol carbonate (GC) is described in the absence of additional hydride sources. The described reduction provides a sustainable route to produce industrially-valuable formate and lactate with high turnover numbers (TONs). The bimetallic Ir(I) involving triNHC carbene ligands exhibits high TONs, and the reaction mechanism, including the bimetallic Ir(triNHC) catalyst, is proposed based on mechanistic studies.

Cover Feature: Aluminum‐Ligand Cooperative O−H Bond Activation Initiates Catalytic Transfer Hydrogenation (ChemCatChem 13/2022)

The Cover Feature shows a pincer ligand framework with Al which cooperatively activates O−H bonds in alcohols. In their Research Article, C. R. Carr et al. demonstrate that transfer hydrogenation is initiated by Al–ligand cooperative bond activations steps to generate the active catalytic species and generate diphenylmethanol from benzophenone. Kinetic experiments support an ordered cyclic transition state, supported by polar solvents, for concerted hydride transfer and there is no evidence for an Al-hydride intermediate. The results highlight the versatility of the diiminopyridine Al platform and open the possibility for expanded substrate scope in transfer hydrogenation catalysis. More information can be found in the Research Article by C. R. Carr et al.

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.

Magnetic Nanoparticles Supported on g‐C3N4 : An Efficient Heterogeneous Catalyst for Selective Transfer Hydrogenation of Furfural to Furfuryl alcohol

AbstractA series of economic and environmental benign g‐C3N4 supported magnetic ferrite nanoparticles (Fe3O4@g‐C3N4) were synthesized for the catalytic transfer hydrogenation of furfural (FF) into furfuryl alcohol (FFA) using ethanol as a source of hydrogen donor and solvent. The unique feature of high nitrogen content and locally conjugated structure of the g‐C3N4 have made it excellent support for loading of small sized ferrite nanoparticles. Excellent furfural conversion of 95.6 % was obtained with 100 % selectivity of the required product furfuryl alcohol over this Fe3O4@g‐C3N4 nanoparticles having mass ratio 0.2 of Fe3O4@g‐C3N4. The high surface properties, uniform dispersion of ferrite and very high ability of adsorption of furfural over g‐C3N4 attributed to the effective catalytic activity. The effect of iron content, catalyst amount, solvent, temperature and reaction time on the CTH of furfural were studied. The synthesized catalysts were characterised by various physic‐chemical, spectroscopic and microscopic techniques.

Synergetic effect of Cu0 −Cu+ derived from layered double hydroxides toward catalytic transfer hydrogenation reaction

As a safe and environmentally friendly selective hydrogenation method, catalytic transfer hydrogenation (CTH) has aroused great interest in preparation of high-value-added products from biomass derived resources. Herein, a Cu-based catalyst (Cu/CuAl-MMO-400) was prepared by structural topological transformation of layered double hydroxides (LDHs) precursor, which displayed promising catalytic behavior toward CTH reaction of furfural (FAL) with 2-propanol (2-POL) as the hydrogen donor. Notably, the reaction rate is as high as 0.125 mol g−1 h−1, which is superior to previously reported non-noble metal catalysts. A combination investigation based on XPS, XANES and Bader charge confirms the co-existence of Cu0 and Cu+ sites on the surface of Cu nanoparticles. Both experimental studies (in situ DRIFTS and isotope labelling MS) and DFT calculations reveal that the Cu0−Cu+ synergistic effect plays a vital role in determining catalytic behavior: the Cu+ species acts as both dehydrogenation and hydrogenation active site; while the Cu0 site promotes the transfer of H atoms between adsorbed substrates. This work substantiates a Cu0 −Cu+ synergetic catalysis by establishing structure-property correlation and revealing reaction pathway, which could be extended to other CTH reactions in the upgrading processes of biomass.

Simultaneous Coordination of Zn(II) and Zr(IV) to d-Amino Acid Oxidase: Highly Efficient Catalytic Transfer Hydrogenation of Levulinic Acid to γ-Valerolactone

Simultaneous Coordination of Zn(II) and Zr(IV) to <scp>d</scp>-Amino Acid Oxidase: Highly Efficient Catalytic Transfer Hydrogenation of Levulinic Acid to γ-Valerolactone

Single-chain chiral Ru-Cu star polymers for highly efficient catalytic aqueous asymmetric transfer hydrogenation

It is of great research value to design simulated enzyme catalysts with high catalytic activity, high selectivity and that are reusable in water. In this work, a star-shaped thermal responsive polymer-Ru/diamine functional intelligent chiral catalyst was synthesized by controlled atom transfer radical polymerization (ATRP). Polymerization can be controlled through self-catalysis of chiral monomers and polymers. Because of the complex that forms between the chiral polymer and Cu2+, the synthesized star polymer experiences a chiral amplification effect. At the same time, the star Ru-Cu catalyst can be assembled into single-chain polymers in water, which showed better catalytic activity and selectivity than the Ru catalyst for aqueous asymmetric reactions, and can be recycled up to six times. Our work provides a new method for controllable synthesis of chiral polymers without additional ligands and the need to remove Cu2+ at the end of the reaction, making the method green and more cost-effective. In summary, bimetallic nanocatalysts were controllably constructed by star chiral polymers through the ATRP pathway. This method significantly aids the development of helical chiral polymers and the preparation of high-efficiency enzyme catalysts.

Catalytic Transfer Hydrogenation of 5-Hydroxymethylfurfural with Primary Alcohols over Skeletal CuZnAl Catalysts.

Catalytic transfer hydrogenation (CTH) with alcohols has been increasingly employed as effective tool for biomass upgrading, however, relying predominantly on secondary alcohols. Herein, for the first time skeletal CuZnAl catalysts were employed for the activation of a primary alcohol, ethanol, for the hydrogenation 5-hydroxymethylfurfual (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) under a mild condition. The catalysts were extensively characterized to reveal the structure characteristics and surface compositions. Over 90 % yield of BHMF were obtained over the optimal CuZnAl-0.5 catalyst at the reaction temperatures of 100-120 °C. Reaction kinetics indicated a competitive adsorption between HMF and ethanol on the catalyst surface, with the activation of ethanol being the rate-determining step (apparent activation energy Ea =70.9 kJ mol-1 ). Preliminary adsorption investigation using combined attenuated total reflectance infrared spectroscopy and density functional theory calculation proposed a η2 -(O,O)-aldehyde, furoxy perpendicular configuration of HMF on catalyst surface. The catalyst was further applied to the CTH of various aldehydes to the corresponding alcohols with high yields, demonstrating the broad applicability of the current system.

Intercalation‐Driven Defect‐Engineering of MoS2for Catalytic Transfer Hydrogenation

AbstractCrystal defects are pivotal to boosting catalytic performance and an in‐depth understanding of the working mechanism of transition‐metal chalcogenides (TMDs), but their facile and controllable engineering are yet challenging. Herein, a new route is introduced to engineer defects on MoS2via in situ intercalation during its hydrothermal preparation, accomplishing the efficient catalytic transfer hydrogenation (CTH) of nitroarenes. The combination of multiple structural characterizations demonstrates that the density of S defects can be tuned by the intercalation of ammonium and dimethylamine cations due to lattice strain/distortion and ligand substitution. As a proof of concept, the defect‐dependent catalytic performance is evidenced in the CTH of nitrobenzene with isopropanol, highlighting the significance of coordinatively unsaturated Mo sites in generating reactive chemisorbed H for subsequent hydrogenation. The good efficiency of defective MoS2within a broad substrate scope further verifies the promise of the intercalation‐driven defect‐engineering strategy for designing TMDs‐based catalysts.

Aluminum‐Ligand Cooperative O−H Bond Activation Initiates Catalytic Transfer Hydrogenation

AbstractMolecular design ultimately furnishes improvements in performance over time, and this has been the case for Rh‐ and Ir‐based molecular catalysts currently used in transfer hydrogenation (TH) reactions for fine chemical synthesis. In this report, we describe a molecular pincer ligand Al catalyst for TH, (I2P2−)Al(THF)Cl (I2P=diiminopyridine; THF=tetrahydrofuran). The mechanism for TH is initiated by two successive Al‐ligand cooperative bond activations of the O−H bonds in two molecules of isopropanol (iPrOH) to afford six‐coordinate (H2I2P)Al(OiPr)2Cl. Stoichiometric chemical reactions and kinetic experiments suggest an ordered transition state, supported by polar solvents, for concerted hydride transfer from iPrO− to substrate. Metal‐ligand cooperative hydrogen bonding in a cyclic transition state is a likely support for the concerted hydride transfer event. The available data does not support involvement of an intermediate Al‐hydride in the TH. Proof‐of‐principle reactions including the conversion of isopropanol and benzophenone to acetone and diphenylmethanol with 90 % conversion in 1 h are described. The analogous hydride compound, (I2P2−)Al(THF)H, also cleaves the O−H bond in iPrOH to afford (HI2P−)Al(OiPr)H and (HI2P−)Al(OiPr)2, but no activity for catalytic TH was observed.

Efficient Catalytic Transfer Hydrogenation of Acetophenone to 1-Phenylethanol over Cu–Zn–Al Catalysts

Cu–Zn–Al catalyst was prepared by the co-precipitation method, and the catalytic performance for transfer hydrogenation of acetophenone (AP) to 1-phenylethanol (1-PhE) was evaluated using isopropanol (IPA) as a hydrogen source. The addition of Zn changed the morphology of the catalyst and reduced aggregation of catalyst particles, resulting in highly dispersed Cu active sites. As the Zn content increased, the valence state of Cu species changed. When the Cu/Zn molar ratio was 2/3, the Cu+/Cu0 ratio in the catalyst was 0.81, resulting in good selectivity for 1-PhE. The reaction conditions were optimized over the Cu–Zn–Al catalyst with a Cu/Zn molar ratio of 2/3. When the reaction was performed at 180 °C for 2 h with an IPA/AP molar ratio of 15, the AP conversion was 89.4% and the 1-PhE selectivity was 93.2%. The Cu–Zn–Al catalyst showed good stability, and AP conversion and the 1-PhE selectivity were essentially unchanged after five cycles.

Rational synthesis of ruthenium-based metallo-supramolecular polymers as heterogeneous catalysts for catalytic transfer hydrogenation of carbonyl compounds

Ruthenium-based metallo-supramolecular polymers (Ru-MSPs) were synthesized by complexing Ru ions with 1,4-bis(1,10-phenanthrolin-5-yl)benzene ligands for heterogeneously catalytic transfer hydrogenation of carbonyl compounds with formate. The degree of polymerization and the local environment of Ru atoms in Ru-MSP were tailored by tuning the ligand/metal ratio and the synthesis temperature/period. The coordinatively-unsaturated Ru atoms are identified as the active centers in Ru-MSP for carbonyl reduction. Ru-MSP is much more active than Ru-based counterparts including its monomeric analogue, which is attributed to (1) the higher electron density in Ru atoms that facilitates the selective dehydrogenation of formate via C-H dissociation, and (2) the lower LUMO of ligand moieties that activates the carbonyl oxygen via Lewis acid-base interactions. Furthermore, Ru-MSP displays high reusability and capability of catalyzing a wide scope of carbonyl compounds. These findings demonstrate that the rationally-designed polymerization is a promising approach to heterogenize the catalytically active metal complexes with enhanced performance.

Catalytic transfer hydrogenation of nitrobenzene over Ti3C2/Pd nanohybrids boosted by electronic modification and hydrogen evolution inhibition

Catalytic transfer hydrogenation (CTH) with formic acid attracts much interest in catalysis, but the sluggish H* production and undesirable H2 evolution reaction (HER) limit its practical applications. Herein we anchored Pd nanoparticles (NPs) on layered Ti3C2 MXene for efficient and selective CTH of nitrobenzene in the presence of formic acid. Some electrons in Pd NPs transferred to Ti3C2 MXene upon formation of Ti3C2/Pd nanohybrids, as confirmed by XPS and DFT simulations. The electron transfer changed Pd valance electron configuration from 4d10 to 4d10-x. Such electron-deficient Pd NPs tuned reaction pathway and promoted formic acid dissociation, both of which favored the production of active H* atoms, i.e., the exact reductant for CTH. Compared with Pd NPs, Ti3C2/Pd showed stronger adsorption of H* and therefore inhibited the occurrence of HER (2H*→H2). Owing to favorable H* production and HER inhibition, Ti3C2/Pd (15 wt% Pd) showed enhanced nitrobenzene CTH performance with turnover frequency of 351.7 h−1 and 99% aniline selectivity, outperforming most of current catalysts. Our work might inspire designing more advanced CTH catalysts by tuning their valance electron configurations with 2D MXene materials.

Zr-MOFs–catalyzed transfer hydrogenation of furfural to furfuryl alcohol: Unveiled performance of DUT-52

Catalytic transfer hydrogenation (CTH) of 2-furfuraldehyde (FALD) at 1 atm has potential industrial applications to produce furfuryl alcohol (FOL) and its derivatives mildly. The process was explored using alcohols in the absence of H2. Solvothermally prepared zirconium(IV) metal organic frameworks (Zr-MOFs) of DUT-52 (DUT: Dresden University of Technology) and UiO-66 (UiO: University of Oslo) were employed in the CTH. Energetic studies (GFN2-xTB level) revealed a similar Gibbs free energy of DUT-52 and UiO-66 when they were reacted by 2-propanol. Electrostatic potential (ESP) charges and Wiberg bond order (WBO) calculations showed that two Zr atoms available for FALD coordination had higher Lewis acidity in DUT-52 than UiO-66. DUT-52 successfully gave >99% of FOL in 3 h at 160 °C under 2-propanol with Ea of 61 kJ/mol and an equal turnover frequency (TOF) to UiO-66 (5.4 h−1). DUT-52 was also easily recyclable up to the 4th run with no significant performance loss.

Solvent-mediated Zr-based coordination polymer with tunable acid properties for the dehydration of fructose and catalytic transfer hydrogenation of 5-hydroxymethylfurfural

In this work, a porous Zirconium based coordination polymer (Zr-ATMP) was facilely synthesized at room temperature with amino tris(methylene phosphonic acid) (ATMP) as ligand, and the surface acidic sites could be adjusted in different solvents. Specifically, the coordination polymer with equivalent content of Bronsted and Lewis acid sites was synthesized in aqueous system, showing high-efficiency catalytic activity for fructose dehydration to 5-hydroxymethylfurfural (HMF). In comparison, the coordination polymer containing an abundance of Lewis acid sites was synthesized in DMF solvent, which efficiently catalyzed the transfer hydrogenation of HMF. Compared to the catalysts preparation in organic solvents, the coordinatively unsaturated Zr4+ could be hydrated in water during catalyst preparation, resulting in the generation of additional Bronsted acid sites at the cost of Lewis acid sites. This contribution proposed a facile approach to prepare Zr-based coordination polymer with tunable acid properties for biomass valorization.

Efficiently catalytic transfer hydrogenation of aryl and heteroaryl halides by ultrafine palladium nanoparticles confined into UiO-66

The hydrodehalogenation of aryl and heteroaryl halides (AHHs) is very crucial for academic and industrial applications. Herein, ultrafine palladium nanoparticles (Pd NPs) with the size distribution about 1.77 ± 0.35 nm, were in-situ synthesized and confined into the metal-organic framework of UiO-66 (named as Pd@UiO-66) by impregnation reduction method without tedious post-reducing step. Pd@UiO-66 shows excellent activity with a high conversion (>90%) efficiency in the catalytic transfer hydrogenation (CTH) of AHHs under mild water systems utilizing ammonium formate as hydrogen donor. Furthermore, Pd@UiO-66 maintains highly excellent stability (conversion >95%) after 5 times reused cycles without losing catalytic activity and leaching Pd nanoparticles. This study supplies a new method for hybrid catalysts by immobilizing ultrafine Pd nanoparticles into crystalline MOFs, displaying efficient transform performance for halogen compounds by catalytic hydrogenation.

Co-Cr composite oxides efficiently catalyzed transfer hydrogenation of α, β-unsaturated aldehydes via N-doped carbon and interfacial electron migration

We present a simple catalyst preparation route, that is spinel-structured CoCrOx (1:2) loaded on N-doped carbon (CoCrOx (1:2)-CN). The as-synthesized CoCrOx (1:2)-CN catalyst promoted catalytic hydrogen transfer (CTH) of cinnamaldehyde (CMA), affording cinnamyl alcohol (CMO) yield as high as 95.3% under mild reaction conditions. There are several reasons for the high yield of CMA: (a) Through interfacial electron migration and N-doped carbon, the acidity and basicity of mesoporous CoCrOx (1:2)-CN catalyst were enhanced, thereby achieving optimal acid-base synergy. (b) Kinetic studies indicated that spinel-structure and N-doped carbon could increase the reaction rate and achieve a low activation energy (69.2 kJ/mol). (c) DFT calculations revealed that both pyridyl-N and pyrrolyl-N doping lowered the energy barrier for adsorption and desorption of reactants resulting in improved catalytic activity. In addition, the CoCrOx (1:2)-CN catalyst showed good reusability.