Ring-opening of (di)benzofurans is a significant area of research in organic chemistry, offering versatile and direct synthetic strategies to access valuable functional phenol derivatives. Transition metal catalysis, particularly nickel-catalyzed reactions, has been extensively explored for the selective cleavage of the C–O bond in (di)benzofuran. Metal-free methods, such as acid catalysis and strong base-mediated process, have also emerged as important alternatives. Organometallic reagents, including Grignard and organolithium reagents, play a pivotal role in promoting efficient C–O bond activation. The field of (di)benzofuran ring opening holds great promise for the synthesis of complex molecules with diverse applications in pharmaceuticals, materials science, and fine chemical synthesis. Continued research efforts will pave the way for innovative strategies and broaden the utility of (di)benzofuran derivatives in various fields.

Density functional theory studies on the reduction of H₂O₂ on a nonheme iron center is shown to lead to dioxygen products efficiently through the formation of a μ-1,2-peroxo bridged diiron(III)dihydroxo complex from two iron(IV)-oxo(hydroxo) intermediates.

Abstract

Hydrogen peroxide is a versatile reductant that under the right conditions can react to form dioxygen in an electrochemical reaction. This reaction has a low carbon footprint and applications are being sought for batteries. In this work a computational study is presented on a recently reported nonheme iron(II) complex where we study mechanistic pathways leading to dioxygen formation from H₂O₂. The work shows that upon reduction of the iron(III)-hydroperoxo species it rapidly leads through heterolytic cleavage of the dioxygen bond to form iron(IV)-oxo(hydroxo). The dimerization reaction of two iron(IV)-oxo(hydroxo) complexes then leads to formation of the dioxygen bond rapidly with small barriers. Dissociation of the dimer expels dioxygen in an exothermic reaction. An alternative mechanism through the formation of a μ-1,2-peroxo-μ-1,1-hydroperoxodiiron(II) intermediate was also tested but found to be highly endergonic. These studies highlight the electrochemical feasibilities of nonheme iron(III)-hydroperoxo complexes.

This study provides a new two-dimensional C−N coupling catalyst for urea production by loading three Mo-atoms on graphdiyne.

Abstract

Synthesis of urea by electrochemical C−N coupling is a promising alternative to the conventional approaches. A metal-cluster catalyst generally possesses multi-atomic active sites and can achieve co-adsorption and activation of several species. As a two-dimensional porous material, graphdiyne (GDY) is predicated to be a good substrate for loading a metal cluster. In this study, tri-metallic Mo-embedded graphdiyne (Mo₃@GDY) stands out for efficient urea synthesis among several TM₃@GDY (TM=Mo, Fe, Co, Ni and Cu), based on density functional theory (DFT) computations. The co-adsorption of side-on N₂ and end-on CO on Mo₃@GDY is benefit to the formation of the urea precursor *NCON with a negative free energy change (−0.66 eV). The final hydrogenation step is the potential-determining step (PDS) with a medium onset potential (-0.71 V). This work extends the application of GDY and first provides a new approach for the electrochemical synthesis of urea by loading tri-metallic atoms on GDY.

A fullerol-based ruthenium complex was prepared, and the heterogeneous (fullerol)-Ru-based water oxidation catalysts (WOC) anchored on the surface of the nano-TiO₂ were developed. Mechanistic studies revealed the anchoring of Ru-based WOC to TiO₂ result in a decrease in the redox potentials of Ru^IV/III couples,a nd decrease the barrier of the crucial O−O bond-forming step, and thus the catalytic activity of the nano-catalysts was improved.

Abstract

Ruthenium polypyridine complexes are the most effective catalysts for the water oxidation reaction (WOR), but the catalytic activity still has a large room for improvement. Herein, a fullerol-based ruthenium complex was prepared by the covalent grafting of the polypyridyl ruthenium complex of water oxidation catalyst (WOC) with fullerol, and the (fullerol)-Ru-based WOCs anchored on the surface of nano-TiO₂ were prepared through a sensitization strategy. The synthesized heterogeneous nano-catalysts are fully characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), infrared spectroscopy (IR), Brunauer–Emmett–Teller (BET) specific surface area and pore size distribution, and diffusion reflection ultraviolet-visible spectrum (DRS). The chemical oxygen evolution experiments reveal that the WOR catalyzed by the catalyst is a first-order reaction with respect to Ce (NH₄)₂(NO₃)₆ (denoted as CAN) concentration when using CAN as the sacrificial oxidant under acidic conditions. The anchoring of Ru-based WOC to TiO₂ result in a decrease in the redox potentials of Ru^IV/III couples, which decrease the barrier of the crucial O−O bond-forming step, and the heterogeneous nano-catalyst exhibit a high catalytic activity with a turnover frequency of 13.4 s⁻¹ and more excellent stability with a 15-min-turn over number of 1054 for TiO₂-fullerol-based ruthenium complex WOC.

Hydroxyapatite (HAP) contains abundant defect sites and easily releases hydroxyl groups to produce new vacancies under calcination at high temperature. The highly dispersed VO_x/HAP catalyst was prepared by an impregnation method using these defects as inducement. VO_x species with different structures were analysed by XRD, XPS, H₂-TPR, Raman and UV–vis spectroscopy. At low calcination temperatures (500 °C and 600 °C), the V species are mainly V₂O₅ crystals. At high calcination temperatures (above 700 °C), VO_x on the HAP surface fills these defect sites and strongly interacts with HAP to form Ca−O−V or P−O−V bands. These scattered defects improved the dispersion of V species. An emphasis is given to the study of the catalytic performances in ODH of cyclohexane over the VHAP catalysts. The highly dispersed VO_x/HAP catalyst showed a high selectivity of cyclohexene, and the selectivity reached 48.2 % when the conversion of was 13.1 % at 410 °C. These improved selectivity is directly related to the chemical environment of highly dispersed VO_x species. In addition, the acidity reduction caused by high temperature calcination leads to the decrease of the adsorption capacity of VHAP to cyclohexene, which promotes the desorption of cyclohexene on the catalyst surface, inhibits the deep oxidation of cyclohexene and improves the selectivity.

Abstract

Hydroxyapatite (HAP) contains abundant defect sites and easily releases hydroxyl groups to produce new vacancies under calcination at high temperature. The highly dispersed VO_x/HAP catalyst was prepared by an impregnation method using these defects as inducement. VO_x species with different structures were analysed by XRD, XPS, H₂-TPR, Raman and UV–vis spectroscopy. At low calcination temperatures (500 °C and 600 °C), the V species are mainly V₂O5 crystals. At high calcination temperatures (above 700 °C), VO_x on the HAP surface fills these defect sites and strongly interacts with HAP to form Ca−O−V or P−O−V bands. These scattered defects improved the dispersion of V species. These highly dispersed VO_x/HAP catalysts were used for oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene. The highly dispersed VOx/HAP catalyst showed a high selectivity for cyclohexene, and the selectivity reached 48.2 % when the conversion of cyclohexane was 13.1 % at 410 °C.

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. The discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAO_Cs3 is reported. The selective oxidation of D-galacturonic acid in a complex mixture is demonstrated.

Abstract

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. For this, effective biocatalysts are in demand. This work reports on the discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAO_Cs3. URAO_Cs3 could be overexpressed using prokaryotic and eukaryotic expression systems. Extensive biochemical characterization revealed that the enzyme displays a high thermostability and an exquisite selectivity for uronic acids, galacturonic acid and glucuronic acid. The enzyme was further investigated by determining the crystal structure. The selective oxidation of D-galacturonic acid in a complex mixture was demonstrated, showing how URAO_Cs3 was found to be highly effective in selectively producing galactaric acid while leaving other carbohydrates untouched. In addition to the specific discovery of URAO_Cs3, these findings suggest that plant proteomes can be an interesting source for new biocatalysts.

A multifunctional heterogeneous Pd-POPs-CF₃SO₃H catalyst containing integrated acid and metal sites and anions was synthesized for tandem conversion of fructose to bio-diketones in good yield with an extraordinary TOF.

Abstract

Tandem conversion of biomass to value-added fine chemicals is a significant challenge. For instance, the production of fine chemicals from fructose involves conversion to 5-hydroxymethylfurfural (5-HMF), followed by another reaction and purification. Dual catalyst systems have been used in nearly every study on the tandem conversion of fructose to bio-diketones. Therefore, a sole multifunctional heterogeneous catalyst was developed in this study for the tandem conversion of fructose to bio-diketones, which has not been reported previously. Instrument corrosion and the separation or purification of 5-HMF were avoided using the multifunctional heterogeneous catalyst, which contained integrated active sites of acid, metal, and anions. The multifunctional CF₃SO₃H-functionalized porous-organic-polymers(POPs)-supported Pd catalyst (Pd-POPs-CF₃SO₃H) was prepared using a series of modifications. A bio-diketone yield of 51.0 % was achieved using Pd-POPs-CF₃SO₃H in the tandem conversion of fructose with an excellent TOF of 88.3 h⁻¹ which is much more efficient than catalyst reported in literatures. Pd-POPs-CF₃SO₃H could be reused at least three times with stable performance. Control experiments and characterization results proved that the high specific surface area, hierarchical pore structure, abundance of CF₃SO₃ ⁻¹ anions, and proximity of Pd moieties and acid sites (“The closer the better” principle) led to the decent performance for bio-diketone.

Fossil fuels depletion and environmental impacts caused by greenhouse gas emissions such as CO2 are significant issues to secure the nature preservation within a sustainable economy. CO2 methanation is a promising process to mitigate CO2 emissions and reuse it to produce CH4, serving as fuel, chemical feedstock, and energy source. A series of LDH-derived Ni-Al catalysts promoted by Li, Mg, Ca, and La were prepared via the co-precipitation method. Characterization by N2 physisorption, X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), as well as thermal techniques as temperature programmed reduction (H2-TPR), desorption (CO2-TPD, H2-TPD), and oxidation (TPO) analyses were performed. Low-temperature catalytic tests (200-400 °C) revealed that alkali metal modification improves performance even at 200 °C, where Ni55Ca11Al33 catalyst achieved 74% CO2 conversion with 100 % CH4 selectivity by enhancing basicity and metal-support interaction, high Ni dispersion and small crystallite sizes, providing proper sites to adsorb and activate CO2. Moreover, the catalysts presented excellent resistance to deactivation, maintaining high stability during 10 h on stream. These results prove that Ni-Al mixed oxides, LDH-derived catalysts performances can be further improved by incorporating alkali metals into less energy-spending, low-temperature CO2 methanation processes.

Significant progress has been made in recent years in the development of liquid metal alloy catalysts. This article provides an overview of the state-of-the-art research pertaining to liquid metal alloy catalysis, including alloy synthesis, reactor design, and theoretical calculations. Different alloy synthesis methods are discussed with a focus on strategies that can achieve colloidal intermetallic structures in liquid metal alloys. Current reactors for liquid metal-based electrocatalytic and thermochemical processes are summarized. The application of theoretical tools, such as machine learning and computational chemistry to further liquid metal alloy design, is discussed. Finally, an outlook on the technological challenges and our perspective on future research opportunities for liquid metal alloy catalysis is presented.

A series of Pd nanoparticles supported on V2O5 immobilized on functionalized carbon, %Pd (1, 3, and 5) and %V2O5 (10, 20, and 30), were prepared by sodium borohydride-assisted microwave polyol synthesis for glycerol oxidation reaction (GlyOR) in an alkaline medium. Electrocatalysts loading, temperature, V2O5 immobilization, and their synergistic effect on the electrocatalytic performance are systematically studied. The electrocatalysts' morphology and electronic properties were investigated using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, Transmission electron microscopy, and X-ray photoelectron spectroscopy. A significantly improved GlyOR is observed with increased V2O5 content and Pd percentage. The 5%Pd/30%V2O5–fAC showed the highest mass activity of 2157.3 mA.mg-1Pd, a more negative onset potential of 0.62 VRHE, versus the commercial equivalent, and possessed high stability and durability. The increase in electrocatalytic activity is attributed to the effective immobilization of V2O5 on fAC efficient synergism between Pd and V2O5, strong metal support interaction (SMSI), and great exposure of the electroactive sites. The results herein contribute significantly to the understanding of the physicochemical and electrochemical effects of metal oxide immobilization, microwave irradiation, %Pd/%Metal oxide optimization, and SMSI on metal oxide-carbon hybrid electrocatalysts for GlyOR, opening new avenues for fabricating high-performance direct alkaline glycerol fuel cells.