Hybrid Catalyst System Research Articles

Production of 5-hydroxymethylfurfural and 2,5-dimethylfuran from fructose using wine lees-derived C-SO3H and Pt5Fe5/C catalyst

Direct production of 2,5-dimethylfuran (DMF) from fructose is crucial for developing biomass-derived fuels, yet it presents significant challenges due to the need for multifunctional active sites for dehydration and hydrodeoxygenation. Meanwhile, the disposal of wine lees, a major winemaking by-product, incurs substantial costs. Herein, a hybrid catalyst system of sulfonated wine lees carbon (WLC-SO3H) and PtFe/C was introduced, achieving a DMF yield of 66.4 % directly from fructose. WLC-SO3H, with enhanced Brønsted acidity, demonstrated high activity in dehydrating fructose to 5-hydroxymethylfurfural (HMF) with a 98.2 % yield. PtFe/C effectively catalyzed the hydrodeoxygenation of HMF to DMF, driven by the strong interaction between Pt and Fe species. This interaction was confirmed through in situ DRIFTS and theoretical calculations, highlighting the system's superior catalytic performance.

Conversion of syngas into lower olefins over a hybrid catalyst system

Conversion of syngas into lower olefins over a hybrid catalyst system

Size‐Dependent Multi‐Electron Donation in Metal‐Complex Quantum Dots Hybrid Catalyst for Photocatalytic Carbon Dioxide Reduction

AbstractThe effective conversion of carbon dioxide (CO2) into valuable chemical fuels relies significantly on the donation of multiple electrons. Its efficiency is closely linked to both the density and lifetime of excited charge carriers. In this study, a hybrid catalyst system comprising covalently bonded InP/ZnS quantum dots (QDs) and Re‐complexes is showcased. The electronic band alignment between the QDs and the Re‐complexes is revealed to dominate the multi‐electron transfer process for photocatalytic conversion to methane (CH4). Notably, the size of the QDs is found to be a determining parameter. Among the three QD sizes investigated, transient absorption spectroscopy studies unveil that rapid multi‐electron transfer from the QDs to the Re‐catalyst occurs in smaller QDs (2.3 nm) due to the substantial driving force. Consequently, the photocatalytic conversion of CO2 to CH4 is significantly enhanced with a turnover number of 6, corresponding to the overall apparent quantum yield of ≈1%. This research underscores the possibilities of engineering multi‐electron transfer by manipulating the electronic band alignment within a catalytic system. This can serve as a guide for optimizing photocatalytic CO2 reduction.

Recent Advances and Perspectives in Ru Hybrid Electrocatalysts for the Hydrogen Evolution Reaction

The water-splitting reaction for green hydrogen generation requires highly efficient catalysts on the side for the hydrogen evolution reaction (HER), and metal ruthenium (Ru) is considered a promising catalyst as a result of its similar property in hydrogen-bonding ability but low cost compared to Pt-based materials. The performance is further boosted by the recently developed hybrid Ru-based electrocatalysts. To reveal the relationship between the hybrid catalyst systems and activity for Ru-based catalysts, the research progress of heterostructured Ru hybrid catalysts in the HER is reviewed in this effort. The enhancement of HER activity of Ru hybrid catalysts is first described on the basis of the synergistic effect, strain effect, and electronic effect, and then, the latest progress is discussed in three categories of single ruthenium catalysts, ruthenium-related compounds, and ruthenium alloy catalysts. It is concluded that the heterostructured interface engineering strategy plays an important role in enhancing the activity of Ru-based catalysts in the HER. In the end, the actual problems and challenges are discussed, e.g., the intrinsic activity and stability, application in the real device, etc. It is recommended to pay attention to the long-term stability, performance, and structural evolution as well as the application of the catalysts in the devices. It is hoped that this effort will help with understanding the progress of Ru-based hybrid catalysts in the field of HER catalysis.

Linear‐Selective Allylation of Aldehydes with Simple Alkenes Mediated by Quadruple Hybrid Catalysis

AbstractIn this study, we developed a linear‐selective allylation reaction of aldehydes using simple alkenes as starting materials by using a quadruple hybrid catalyst system. The reaction proceeded under mild conditions such as room temperature under visible light irradiation and was applicable to asymmetric reactions. The key for this reaction is the addition of Ni(BF4)2 ⋅ 6H2O catalyst to the previously reported ternary catalyst system, accelerating the allylic transfer process from branch products to thermodynamically stable linear products by increasing the Brønsted acidity of thiophosphoric imide (TPI) catalyst.magnified image

A Catalytic Alkylation of Ketones via sp3 C-H Bond Activation.

We identified a ternary hybrid catalyst system composed of an acridinium photoredox catalyst, a thiophosphoric imide (TPI) catalyst, and a titanium complex catalyst that promoted an intermolecular addition reaction of organic molecules with various ketones through sp3 C-H bond activation. The thiyl radical generated via single-electron oxidation of TPI by the excited photoredox catalyst abstracted a hydrogen atom from organic molecules such as toluene, benzyl alcohol, alkenes, aldehydes, and THF. The thus-generated carbon-centered radical species underwent addition to ketones and aldehydes. This intrinsically unfavorable step was promoted by single-electron reduction of the intermediate alkoxy radical by catalytically generated titanium(III) species. This reaction provided an efficient and straightforward route to a broad range of tertiary alcohols and was successfully applied to late-stage functionalization of drugs or their derivatives. The proposed mechanism was supported by both experimental and theoretical studies.

Photoelectrochemical CO2 Reduction Products Over Sandwiched Hybrid Ga2O3:ZnO/Indium/ZnO Nanorods

Recycled valuable energy production by the electrochemical CO2 reduction method has explosively researched using countless amounts of developed electrocatalysts. Herein, we have developed hybrid sandwiched Ga2O3:ZnO/indium/ZnO nanorods (GZO/In/ZnONR) and tested their photoelectrocatalytic CO2 reduction performances. Gas chromatography and nuclear magnetic spectroscopy were employed to examine gas and liquid CO2 reduction products, respectively. Major products were observed to be CO, H2, and formate whose Faradaic efficiencies were highly dependent on the relative amounts of overlayer GZO and In spacer, as well as applied potential and light irradiation. Overall, the present study provides a new strategy of controlling CO2 reduction products by developing a sandwiched hybrid catalyst system for energy and environment.

Cooperation of multi-walled carbon nanotubes and cobalt doped TiO2 to activate peroxymonosulfate for antipyrine photocatalytic degradation

• The photocatalyst was prepared through simple physical mixing of MWCNT and Co-TiO 2 . • The two catalyst have shown an obvious synergistic effect in the degradation process. • e − transferred between Co-TiO 2 and MWCNT clusters promoted the activation of PMS. • • O 2 − generated by MWCNT could accelerate the Co 3+ /Co 2+ redox cycles on Co-TiO 2 . • This study provided new ideas to use the catalyst more effectively. A hybrid catalyst system consisted of MWCNT and Co-TiO 2 through simple physical mixing was applied for peroxymonosulfate activation for antipyrine degradation. With 2 mM peroxymonosulfate, the removal rate of antipyrine is significantly increased from 53.24% and 86.23% to 100% in the presence of same weight of 0.2 g/L MWCNTs, Co-TiO 2 , and MWCNTs/Co-TiO 2 (half/half) mixture, respectively in 12 min. The influence of various parameters, including the ratio of Co-TiO 2 /MWCNT, catalyst dose, peroxymonosulfate dose, antipyrine concentration, and initial pH, were further investigated in detail. The underlying catalytic mechanism of the synergistic effect was unraveled by quenching tests and EPR analysis. It was attributed to the electrons tranferration between Co-TiO 2 and MWCNT, and the acceleration of Co 3+ /Co 2+ by generated superoxide. This work not only provides a novel and efficient method of pharmaceutical wastewater treatment, but also reveals a new perspective to use the catalyst more efficiently.

G–C3N4 induced acceleration of Fe3+/Fe2+ cycles for enhancing metronidazole degradation in Fe3+/peroxymonosulfate process under visible light

In this study, a Fe3+/g-C3N4 hybrid catalyst system was proposed to activate peroxymonosulfate (PMS) for the metronidazole (MNZ) photocatalytic degradation. The two catalysts, Fe3+ and g-C3N4, exhibited an obvious synergistic effect in the photocatalytic degradation process. When 1 mM PMS, 0.04 mM Fe3+ and 0.05 g L−1 g-C3N4 were applied, the rate constant of the Fe3+/g-C3N4/PMS/LED process at 0.07288 min−1 is around 3.6 to 6.8 times faster than that of Fe3+/PMS/LED and g-C3N4/PMS/LED processes at 0.0198 and 0.01076 min−1, respectively. Under visible light, electron transfer from photo-activated g-C3N4 to Fe3+, resulting in the continuous regeneration of Fe2+ in the system, which ensures non-stopping production of radicals for MNZ degradation. UV–visible spectra were used to confirm the regeneration of Fe2+. In addition, EPR tests were used to identify the reactive oxygen species involved in the reaction system. Typically, the effects of various operation parameters, including the catalyst dosage, PMS dosage, initial concentration of MNZ and initial pH were examined. This work provided a new idea of promoting pollutant degradation by accelerating Fe3+/Fe2+ redox through semiconductor, which could help to use the catalyst more effectively for wastewater treatment and/or chemical industries.

Data-driven catalyst optimization for stereodivergent asymmetric synthesis by iridium/boron hybrid catalysis

Asymmetric catalysis enabling divergent control of multiple stereocenters remains challenging in synthetic organic chemistry. Although machine-learning-based optimization of molecular catalysis is a rapidly growing research field, the use of such approaches for catalyst design to achieve stereodivergent asymmetric synthesis producing multiple reaction outcomes, such as constitutional selectivity, diastereoselectivity, and enantioselectivity, is unprecedented. Here, we report the straightforward identification of asymmetric two-component iridium/boron hybrid catalyst systems for α- C -allylation of carboxylic acids. Structural optimization of the chiral ligands for iridium catalysts was driven by molecular-field-based regression analysis with a dataset containing overall 32 molecular structures. The catalyst systems enabled selective access to all the possible isomers of chiral carboxylic acids bearing contiguous stereocenters. This chemoselective and stereodivergent, asymmetric catalysis is applicable to late-stage structural modifications of drugs and their derivatives. Practical regression-based, data-driven, chiral catalyst design and optimization method 3-Dimensional, quantitative structure-selectivity relationships and molecular field analysis Control/improvement of four reaction outcomes with regression analysis Stereodivergent asymmetric synthesis of α-allyl carboxylic acids Chen et al. report that data-driven catalyst design facilitates stereodivergent asymmetric synthesis, which remains challenging in organic synthesis. This research indicates that digital transformations (DXs) of organic synthesis (e.g., the use of machine-leaning and materials-informatics techniques) enable analysis and control of complicated reactions, opening new avenues in molecular catalysis.

Study of catalyst performance of two inorganic/organic and inorganic/inorganic hybrid catalysts on the CO2 cycloaddition to propylene oxide: kinetics and thermodynamics

The behavior of two hybrid catalysts: inorganic/organic (KI/chitin) and inorganic/inorganic (KI/amorphous silica-alumina) on the CO2 cycloaddition to Propylene oxide has been compared. Conversions of KI/chitin and KI/Si-Al were 99 and 97% respectively. KI/Si-Al shows a type IV N2 adsorption isotherm at P0/P of 0.6-0.9 of mesoporous nature with a significant concentration of Lewis acid sites, its FT-IR analysis shows that CO2 can be adsorbed as organic “bridging” carbonate onto the support’s surface, which has an important role in the reaction mechanism. Kinetic analysis shows that the organic co-catalyst is up to 1.5 times faster for the CO2 cycloaddition than the inorganic co-catalyst at 160 °C bu both show very similar rate at 120 °C. Both supported catalysts show a significantly lower Ea than that calculated for free KI, although both show comparable activation energies. This insight gives interesting findings on how hybrid catalyst systems behave in an utmost crucial CO2 fixation reaction, being the foundations of future investigation on scale-up applications.

A Hybrid Ru(II)/TiO2 Catalyst for Steadfast Photocatalytic CO2 to CO/Formate Conversion Following a Molecular Catalytic Route

Herein, we employed a molecular Ru(II) catalyst immobilized onto TiO2 particulates of (4,4'-Y2-bpy)RuII(CO)2Cl2 (RuP; Y = CH2PO(OH)2), as a hybrid catalyst system to secure the efficient and steady catalytic activity of a molecular bipyridyl Ru(II)-complex-based photocatalytic system for CO2 reduction. From a series of operando FTIR spectrochemical analyses, it was found that the TiO2-fixed molecular Ru(II) complex leads to efficient stabilization of the key monomeric intermediate, RuII-hydride (LRuII(H)(CO)2Cl), and suppresses the formation of polymeric Ru(II) complex (-(L(CO)2Ru-Ru(CO)2L)n-), which is a major deactivation product produced during photoreaction via the Ru-Ru dimeric route. Active promotion of the monomeric catalytic route in a hetero-binary system (IrPS + TiO2/RuP) that uses TiO2-bound Ru(II) complex as reduction catalyst led to highly increased activity as well as durability of photocatalytic behavior with respect to the homogeneous catalysis of free Ru(II) catalyst (IrPS + Ru(II) catalyst). This catalytic strategy produced maximal turnover numbers (TONs) of >4816 and >2228, respectively, for CO and HCOO- production in CO2-saturated N,N-dimethylformamide (DMF)/TEOA (16.7 vol % TEOA) solution containing a 0.1 M sacrificial electron donor.

Three-dimensional porous ultrathin carbon networks reinforced PBAs-derived electrocatalysts for efficient oxygen evolution

Prussian blue analogues (PBAs), identified with a face-centered cubic (fcc) unit cell with transition-metal ions bridged by cyano ligands, can be used as precursors in nanomaterials for catalysis applications, but the performance is usually limited by the original large size of PBAs. We provide here a controllable thermal decomposition route for PBAs to obtain highly dispersed small-sized nanoparticles with high catalytic activity. CoFe PBA nanocubes as catalyst precursors are grown within three-dimensional porous ultrathin N-doped carbon networks (3DNC), which is constructed using mixed soluble salts as templates. The use of 3DNC as supporting matrix can not only increase the electrical conductivity and transport properties of reaction-relevant species within the catalyst material, but also supply huge specific surface and restrict the size of loaded nanoparticles. Followed by calcination in the reductive atmosphere, the PBA nanocubes are decomposed to form numerous small-sized CoFe/CoFeOx nanoparticles that are uniformly dispersed. It is interesting to find that this thermal decomposition process is assisted by 3DNC matrix because of its excellent thermal conductive property. Benefiting from the synergetic bimetal alloy/oxide composition, advantageous structural feature and favorable interfacial integration of the hybrid material, the CoFe/CoFeOx@3DNC exhibits remarkable electrocatalytic activity and stability for the oxygen evolution reaction (OER) in alkaline media. The decomposition of PBAs precursor to small-sized nanoparticles and the use of 3DNC as supporting matrix and thermal conductive agent are appealing. The integration of these two components provides an interesting hybrid catalyst system with controllable composition, delicate morphology and favorable interfacial property.

Au/Pt Bimetallic Nanoparticle Decorated Microparticle Hybrid Catalyst System for Heterogeneous Hydrogenation of Styrene

Poly(methacryloyloxy quinoline) microparticles were synthesized and used as reducing and stabilizing agents to prepare Au/Pt bimetallic nanoparticle (NP) decorated microparticle (MP) hybrid catalyst systems. These newly reported hybrid catalyst systems were used for reduction of styrene into ethylbenzene. Gold precursor was essential to prepare bimetallic NPs due to its great interaction with PMAQ resulting in the reduction to AuNPs on the surface of PMAQ MPs. Pt is also contrubute to NP formation thanks to this superior interaction between Au and PMAQ MPs. The bimetallic nanoparticle contents on the PMAQ MPs were determined as Au0.85Pt0.15 via XRD analysis. Au and Pt amounts were also determined with ICP-MS analysis. Although the metal amount in the sample was quite low, the catalytic effect was remarkable for hybrid system. AuNP decorated MPs had no catalytic activity for the reduction of styrene. Thus, it is clear that Pt was the active part of hybrid catalyst system for this reaction. On the other hand, gold precursor had been determined as crucial for the simultaneous synthesis of bimetallic NP decorated MPs as well. New microparticles decorated with bimetallic nanoparticles have been synthesized and used effectively as a catalyst systems in the hydrogenation of styrene. While it is reported in the literature that such particles have successful catalytic activity in various oxidations, our particles stand out with reducing activities, reusabilities and easy production/removal properties.

Manganese-catalyzed aziridination of olefins with chloramine-T in water and buffered aqueous solutions

A water-soluble, manganese-porphyrin complex was used to catalytically generate aziridines from olefins in moderate to good yields (up to 93%) upon optimization at room temperature and in aqueous media. Reactions using chloramine-T at slightly acidic to neutral pH values showed generally higher catalytic yields. Attempts to integrate this catalytic system into a DNA hybrid catalyst system to support asymmetric aziridination showed little promise, where steric bulk in the axial positions from activation of chloramine-T by this Mn-heme complex may influence its ability to associate with double-stranded DNA.

Catalytic Allylation of Aldehydes Using Unactivated Alkenes.

Simple feedstock organic molecules, especially alkenes, are attractive starting materials in organic synthesis because of their wide availability. Direct utilization of such bulk, inert organic molecules for practical and selective chemical reactions, however, remains limited. Herein, we developed a ternary hybrid catalyst system comprising a photoredox catalyst, a hydrogen-atom-transfer catalyst, and a chromium complex catalyst, enabling catalytic allylation of aldehydes with simple alkenes, including feedstock lower alkenes. The reaction proceeded under visible-light irradiation at room temperature and with high functional group tolerance. The reaction was extended to an asymmetric variant by employing a chiral chromium complex catalyst.

Cu-CuOx/rGO catalyst derived from hybrid LDH/GO with enhanced C2H4 selectivity by CO2 electrochemical reduction

Electrochemical CO2 conversion to value-added fuels and chemicals enabled by suitable heterogeneous catalysts has attained great attention given its economic viability and overall process efficiency. Herein, we have designed a new electro-catalyst ER-Cu5-LDH/rGO using electro-reduction method from Cu5Al-CO3 hybrid LDH/GO precursor for efficient CO2 reduction reaction (CO2RR). Interestingly, the ER-Cu5-LDH/rGO catalyst presented a higher C2H4 production selectivity than the ER-Cu5-LDH catalyst without rGO. The obtained ER-Cu5-LDH/rGO exhibited a high C2H4 faradaic efficiency (FE) up to 54 % and a high C2H4 partial current density of ‒11.64 mA/cm2 at ‒1.2 V vs. RHE. It also exhibited excellent stability up to 50 h. The total FE of gaseous and liquid products for ER-Cu5-LDH/rGO is closed to 100 %. The morphological changes during CO2RR were monitored using SEM analyses for catalyst stability examination. The influence of electrolyte or pH on the electro-catalytic performance of ER-Cu5-LDH/rGO were studied. In order to reflect the superiority of LDH precursors, a control catalyst containing Cu2O supported on rGO (ER-Cu2O/rGO) was prepared and comparatively studied. Overall, our hybrid catalyst system ER-Cu5-LDH/rGO is very promising materials for CO2 conversion to C2H4, displaying remarkable FE, high C2H4 partial current density, and the excellent stability. Such a commendable behavior is ascribed to the excellent dispersion of active copper species as well as the superior electric conductivity of rGO.

A Bond-Weakening Borinate Catalyst that Improves the Scope of the Photoredox α-C–H Alkylation of Alcohols

The development of catalyst-controlled, site-selective C(sp3)–H functionalization reactions is currently a major challenge in organic synthesis. In this paper, a novel bond-weakening catalyst that recognizes the hydroxy group of alcohols through formation of a borate is described. An electron-deficient borinic acid–ethanolamine complex enhances the chemical yield of the α-C–H alkylation of alcohols when used in conjunction with a photoredox catalyst and a hydrogen atom transfer catalyst under irradiation with visible light. This ternary hybrid catalyst system can, for example, be applied to functional-group-enriched­ peptides.

Catalytic Acceptorless Dehydrogenation of Aliphatic Alcohols.

We developed the first acceptorless dehydrogenation of aliphatic secondary alcohols to ketones under visible light irradiation at room temperature by devising a ternary hybrid catalyst system comprising a photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst. The reaction proceeded through three main steps: hydrogen atom transfer from the α-C-H bond of an alcohol substrate to the thiyl radical of the photo-oxidized organocatalyst, interception of the generated carbon-centered radical with a nickel catalyst, and β-hydride elimination. The reaction proceeded in high yield under mild conditions without producing side products (except H2 gas) from various alcohols, including sterically hindered alcohols, a steroid, and a pharmaceutical derivative. This catalyst system also promoted acceptorless cross-dehydrogenative esterification from aldehydes and alcohols through hemiacetal intermediates.

Preliminary evaluation of a commercially viable Co-based hybrid catalyst system in Fischer–Tropsch synthesis combined with hydroprocessing

A hybrid catalyst for one-step conversion of syngas into liquid hydrocarbons, mainly gasoline and diesel, is proposed.