Aerobic Oxidation of Biomass-Derived 5-(Hydroxymethyl)furfural into 2,5-Diformylfuran Catalyzed by the Trimetallic Mixed Oxide (Co–Ce–Ru)

Highly efficient electrocatalytic biomass valorization over a perovskite-derived nickel phosphide catalyst

In this work, we successfully develop a binder-free phosphorus-engineered perovskite-based catalyst grown on nickel foam via a hydrothermal-phosphorization strategy. For the first time, an as-synthesized perovskite-based nickel phosphide catalyst exhibits excellent electrocatalytic oxidation (ECO) performance for biomass valorization to supersede the competitive oxygen evolution reaction (OER).

Research Progress of Highly Efficient Noble Metal Catalysts for the Oxidation of 5-Hydroxymethylfurfural

5-hydroxymethylfurfural (HMF) is considered to be one of the most pivotal multifunctional biomass platform chemicals. This Review discusses recent advances in catalytic oxidation of HMF towards high-value products. The reaction mechanism of different noble metals and the path of HMF oxidation to high-value products have been deeply investigated in the noble metal catalytic system. The reaction mechanisms of different noble metals and HMF conversion paths were compared in detail. Moreover, the factors affecting the performance of different noble metal catalysts were summarized. Finally, effective strategies were put forward to improve the catalytic performance of noble metal catalysts. The purpose is to provide a valuable reference for the academic research on the preparation of oxidation products from biomass-based HMF and the industrial application of noble metal catalysts.

Recent Approaches in the Catalytic Transformation of Biomass-Derived 5-Hydroxymethylfurfural into 2,5-Diformylfuran

The conversion of biomass into a great variety of valuable chemicals, polymers, and fuels gives a sustainable alternative for the insufficiency of non-renewable fossil fuel resources and reduces environmental pollution. 5-Hydroxymethylfurfural (HMF), converted from sustainable carbohydrates, is a significant building block chemical, and the selective oxidation of HMF into 2,5-diformylfuran (DFF) presents an ongoing challenge. DFF is a versatile platform molecule derived from biomass and has promising application in pharmaceuticals and polymers. This Review provides an overview of the latest developments of efficient catalytic systems for the sustainable conversion of HMF to DFF.

Electro- and Photocatalytic Oxidative Upgrading of Bio-based 5-Hydroxymethylfurfural

Conversion of biomass into biofuels and high value-added chemicals is a promising strategy to solve the increasingly deteriorating environmental problems caused by fossil energy consumption. The development of efficient technologies and methods is the premise and guarantee to realize the high-value conversion of biomass. 5-Hydroxymethylfurfural (HMF), as a versatile biomass platform compound, is generated via dehydration of hexoses (e. g., fructose and glucose) derived from cellulosic biomass. This Review gives an overview of the advances and challenges of electro- and photocatalytic oxidation of biomass-derived HMF to high-value chemicals such as 2,5-formylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). These strategies and methods for the preparation of high-value chemicals by electro- and photocatalytic oxidation of HMF, coupled with, for example, hydrogen evolution reaction, organic substrate reduction, CO₂ reduction reaction, or N₂ reduction reaction, were summarized and discussed. Moreover, the catalytic efficiency and mechanism of different types of catalysts were also introduced in these conversion systems.

Phosphorus vacancy-engineered Ce-doped CoP nanosheets for the electrocatalytic oxidation of 5-hydroxymethylfurfural

The electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furanedioic acid (FDCA) has received increasing attention. To achieve satisfactory electrooxidation of HMF, the development of an efficient electrocatalyst is particularly critical. Herein, porous Ce-CoP nanosheets integrating Ce doping and P vacancies are designed through a deep eutectic solvent approach, and they allow the excellent electrocatalytic oxidation of HMF to FDCA in 1 M KOH electrolyte with 100% HMF conversion, 98% FDCA yield, and a faradaic efficiency of 96.4% at low potential.

Molybdenum carbide anchored on glucose-derived carbon (β-Mo2C@C) as a bifunctional catalyst for conversion of fructose to 2,5-diformylfuran

Molybdenum carbide anchored on glucose-derived carbon (β-Mo2C@C) has been successfully synthesized and applied as a bifunctional catalyst for one-pot conversion of fructose to DFF.

Hydroxyapatite-Supported Polyoxometalates for the Highly Selective Aerobic Oxidation of 5-Hydroxymethylfurfural or Glucose to 2,5-Diformylfuran under Atmospheric Pressure

(NH4 )5 H6 PV8 Mo4 O40 supported on hydroxyapatite (HAP) (PMo4 V8 /HAP (n)) was prepared through the ion exchange of hydroxy groups. This ion exchange favored the oxidative conversion of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF) in a one-pot cascade reaction with 96.0 % conversion and 83.8 % yield under 10 mL/min of O2 flow. PMo4 V8 /HAP (31) was used to explore the production of DFF directly from glucose with the highest yield of 47.9 % so far under atmospheric oxygen, whereas the yield of DFF increased to 54.7 % in a one-pot and two-step reaction. These results indicated that the active sites in PMo4 V8 /HAP (31) retained their activities without any interference toward one another, which enabled the production of DFF in a more cost-saving way by only using oxygen and one catalyst in a one-step reaction. Meanwhile, the rigid structure of HAP and strong interaction in PMo4 V8 /HAP (31) allowed this catalyst to be reused for at least six times with high stability and duration.

Aerobic oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran using manganese dioxide with different crystal structures: A comparative study

Aerobic oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF) using O₂ gas represents a sustainable approach for valorization of lignocellulosic compounds. As manganese dioxide (MnO₂) is validated as a useful oxidation catalyst and many crystalline forms of MnO₂ exist, it is critical to explore how the crystalline structures of MnO₂ influence their physical/chemical properties, which, in turn, determine catalytic activities of MnO₂ crystals for HMF oxidation to DFF. In particular, six MnO₂ crystals, α-MnO₂, β-MnO₂, γ-MnO₂, δ-MnO₂, ε-MnO₂, and λ-MnO₂ are prepared and investigated for their catalytic activities for HMF oxidation to DFF. With different morphologies and crystalline structures, these MnO₂ crystals possess very distinct surficial chemistry, redox capabilities, and textural properties, making these MnO₂ exhibit different catalytic activities towards HMF conversion. Especially, β-MnO₂ can produce much higher DFF per surface area than other MnO₂ crystals. β-MnO₂ could achieve the highest C_HMF = 99% and Y_DFF = 97%, which are much higher than the reported values in literature, possibly because the surficial reactivity of β-MnO₂ appears to be highest in comparison to other MnO₂ crystals. Especially, β-MnO₂ could exhibit Y_DFF > 90% over 5 cycles of reusability test, and maintain its crystalline structure, revealing its advantageous feature for aerobic oxidation of HMF to DFF. Through this study, the relationship between morphology, surface chemistry, and catalytic activity of MnO₂ with different crystal forms is elucidated for providing scientific insights into design, application and development of MnO₂-based materials for aerobic oxidation of bio-derived molecules to value-added products.

Theoretical study on molecular mechanism of aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformyfuran catalyzed by VO2+ with counterpart anion in N,N-dimethylacetamide solution

Vanadium-containing catalysts exhibit good catalytic activity toward the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformyfuran (DFF). The aerobic oxidation mechanism of HMF to DFF catalyzed by VO₂⁺ with counterpart anion in N,N-dimethylacetamide (DMA) solution have been theoretically investigated. In DMA solution, the stable VO₂⁺-containing complex is the four-coordinated [V(O)₂(DMA)₂]⁺ species. For the gross reaction of 2HMF + O₂ → 2DFF + 2H₂O, there are three main reaction stages, i.e., the oxidation of the first HMF to DFF with the reduction of [V(O)₂(DMA)₂]⁺ to [V(OH)₂(DMA)]⁺, the aerobic oxidation of [V(OH)₂(DMA)]⁺ to the peroxide [V(O)₃(DMA)]⁺, and the oxidation of the second HMF to DFF with the reduction of [V(O)₃(DMA)]⁺ to [V(O)₂(DMA)₂]⁺. The rate-determining reaction step is associated with the C–H bond cleavage of –CH₂ group of the first HMF molecule. The peroxide [V(O)₃(DMA)]⁺ species exhibits better oxidative activity than the initial [V(O)₂(DMA)₂]⁺ species, which originates from its narrower HOMO–LUMO gap. The counteranion Cl⁻ exerts promotive effect on the aerobic oxidation of HMF to DFF catalyzed by [V(O)₂(DMA)₂]⁺ species.

The rate-determining reaction step is associated with the C–H bond cleavage of –CH₂ group of the first HMF molecule oxidized by [V(O)₂(DMA)₂]⁺ species, while counteranion Cl⁻ exhibits catalytically promotive effect.

The one-step transformation of fructose to 2,5-diformylfuran over Ru metal supported on montmorillonite

Ruthenium metal supported on a montmorillonite (2 wt% Ru-MMT) catalyst have been synthesized and characterized. Catalyst found to be effective for the one-pot transformation of fructose to DFF showing an excellent yield with good recyclability.

Oxidation of lignocellulosic platform molecules to value-added chemicals using heterogeneous catalytic technologies

This minireview gives an overview about heterogeneous catalytic technologies for the oxidation of key platform molecules (glucose, 5-hydroxymethylfurfural, furfural and levulinic acid) into valuable chemicals.

Metal Nitrate Catalysis for Selective Oxidation of 5-Hydroxymethylfurfural into 2,5-Diformylfuran under Oxygen Atmosphere

Selective synthesis of various versatile compounds from biomass is of great importance to displace traditional fossil fuel resources. Here, homogeneous metal nitrate (M(NO3) x )/(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and M(NO3) x /TEMPO/NaNO2 catalyst systems in glacial acetic acid and acetonitrile, respectively, have been found to be highly active and practically sustainable for selective oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-diformylfuran (DFF) using pure O2 or even O2 in air as the oxidant. The catalytic methods enable full HMF conversion with a nearly 100% DFF selectivity at 50 °C under atmospheric pressure using a very simple reaction setup and workup. Mechanistic aspects are discussed. The influences of reaction conditions such as different metal catalysts, catalyst loading, solvents, and reaction temperature on the promotion effect were studied. Meanwhile, the catalyst systems had also good performance for aerobic oxidation of other alcohols.

Recent Advances in the Development of 5-Hydroxymethylfurfural Oxidation with Base (Nonprecious)-Metal-Containing Catalysts

5-Hydroxymethylfurfural (HMF) is one of the versatile platform molecules that can be derived from biomass, and a promising starting substrate for producing 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). DFF is a platform chemical with applications in pharmaceuticals, macrocyclic ligands, and functional polymeric materials. Importantly, FDCA is being considered as a potential alternative to replace terephthalic acid for producing the bioplastic polyethylene furanoate, instead of polyethylene terephthalate, by blending with ethylene glycol. A significant number of studies have focused on the oxidation of HMF to FDCA with metal-containing heterogeneous catalysts in both aqueous and organic media in the presence of peroxides/air/molecular oxygen as the oxidant. In this regard, articles have recently been published related to HMF oxidation with base (nonprecious)-metal-containing catalysts that exhibit appealing activity towards DFF or FDCA in terms of yield. Thus, this Minireview focuses on recent developments in efficient transformations of HMF to DFF and FDCA with base-metal-containing heterogeneous catalysts in aqueous and organic media. This review further focuses on the direct transformation of glucose/fructose to DFF and/or FDCA with nonprecious-metal-containing catalysts in various solvents. Photocatalytic approaches for HMF oxidation with nonprecious metal- containing catalysts are also briefly discussed.

Catalytic oxidation of carbohydrates into organic acids and furan chemicals

A review on the development of new routes for the production of organic acids and furan compoundsviacatalytic oxidation reactions.

Porous nitrogen-enriched carbonaceous material from marine waste: chitosan-derived carbon nitride catalyst for aerial oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid

Chitosan-derived, porous nitrogen-enriched carbonaceous carbon nitride catalyst (PCNx) has been synthesized from marine waste and its use demonstrated in a metal-free heterogeneous selective oxidation of 5-hydroxymethyl-furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) using aerial oxygen under mild reaction conditions.

Oxidation of 5-Chloromethylfurfural (CMF) to 2,5-Diformylfuran (DFF)

2,5-Diformylfuran (DFF) is an important biorenewable building block, namely for the manufacture of new polymers that may replace existing materials derived from limited fossil fuel resources. The current reported methods for the preparation of DFF are mainly derived from the oxidation of 5-hydroxymethylfurfural (HMF) and, to a lesser extent, directly from fructose. 5-Chloromethylfurfural (CMF) has been considered an alternative to HMF as an intermediate building block due to its advantages regarding stability, polarity, and availability from glucose and cellulose. The only reported method for the transformation of CMF to DFF is restricted to the use of DMSO as the solvent and oxidant. We envisioned that the transformation could be performed using more attractive conditions. To that end, we explored the oxidation of CMF to DFF by screening several oxidants such as H₂O₂, oxone, and pyridine N-oxide (PNO); different heating methods, namely thermal and microwave irradiation (MWI); and also flow conditions. The combination of PNO (4 equiv.) and Cu(OTf)₂ (0.5 equiv.) in acetonitrile was identified as the best system, which lead to the formation of DFF in 54% yield under MWI for 5 min at 160 °C. Consequently, a range of different heterogeneous copper catalysts were tested, which allowed for catalyst reuse. Similar results were also observed under flow conditions using copper immobilized on silica under thermal heating at 160 °C for a residence time of 2.7 min. Finally, HMF and 5,5'-oxybis(5-methylene-2-furaldehyde) (OBMF) were the only byproducts identified under the reaction conditions studied.

Nanobelt α-CuV2O6 with hydrophilic mesoporous poly(ionic liquid): a binary catalyst for synthesis of 2,5-diformylfuran from fructose

The task-specific binary catalyst composed of nanobelt α-CuV₂O₆ and hydrophilic mesoporous poly(ionic liquid) exhibited high efficiency and stable activity in the direct synthesis of 2,5-diformylfuran (DFF) from fructose.

Cascade catalysis via dehydration and oxidation: one-pot synthesis of 2,5-diformylfuran from fructose using acid and V2O5/ceramic catalysts

A vanadium pentoxide/ceramic catalyst was synthesized and a one-pot method for the preparation of 2,5-DFF from fructose was developed.

One-Pot Conversion of Carbohydrates into Furan Derivatives via Furfural and 5-Hydroxylmethylfurfural as Intermediates

Recently, there has been growing interest in the transformation of renewable biomass into value-added fuels and chemicals. The catalytic conversion of naturally abundant carbohydrates can generate two-important furan chemicals: 5-hydroxymethylfurfural (HMF) from C6 carbohydrates and furfural from C5 carbohydrates. Both HMF and furfural have received great interest as precursors in the synthesis of commodity chemicals and liquid fuels. In recent years, a trend has emerged to integrate sequential catalytic processes involving multistep reactions for the direct one-pot transformation of carbohydrates into the aimed fuels and chemicals. One-pot reactions have remarkably unique and environmentally friendly benefits, including the fact that isolation and purification of intermediate compounds can be avoided. Herein, the present article aims to review recent advances in the one-pot conversion of carbohydrates into furan derivatives via furfural and HMF as intermediates. Special attention will be paid to the catalytic systems, mechanistic insight, reaction pathways, and catalyst stability. It is expected that this review will guide researchers to develop effective catalytic systems for the one-pot transformation of carbohydrates into furan derivatives.

Theoretical study of the catalytic oxidation mechanism of 5-hydroxymethylfurfural to 2,5-diformylfuran by PMo-containing Keggin heteropolyacid

The mechanism for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) catalysed by PMo-containing Keggin heteropolyacid (H₃PMo₁₂O₄₀) has been systematically investigated at the M06/6-31++G(d,p), Lanl2dz level in dimethylsulfoxide.

Aerobic selective oxidation of 5-hydroxymethyl-furfural over nitrogen-doped graphene materials with 2,2,6,6-tetramethylpiperidin-oxyl as co-catalyst

N-doped graphene materials were prepared via thermal treatment of graphene oxide in flowing NH₃, and their catalytic performance was tested in aerobic oxidation of 5-hydroxymethy-furfural.

Selective aerobic oxidation of HMF to 2,5-diformylfuran on covalent triazine frameworks-supported Ru catalysts

The selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran has been performed under mild conditions at 80 °C and 20 bar of synthetic air in methyl t-butyl ether. Ru clusters supported on covalent triazine frameworks (CTFs) allowed excellent selectivity and superior catalytic activity compared to other support materials such as activated carbon, γ-Al2 O3 , hydrotalcite, or MgO. CTFs with varying pore size, specific surface area, and N content could be prepared from different monomers. The structural properties of the CTF materials influence the catalytic activity of Ru/CTF significantly in the aerobic oxidation of HMF, which emphasizes the superior activity of mesoporous CTFs. Recycling of the catalysts is challenging, but promising methods to maintain high catalytic activity were developed that facilitate only minor deactivation in five consecutive recycling experiments.

Ruthenium complex immobilized on poly(4-vinylpyridine)-functionalized carbon-nanotube for selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

Ruthenium complex, immobilized on poly(4-vinylpyridine)-functionalized carbon-nanotube, shows excellent catalytic performance towards selective aerobic oxidation of biomass-based 5-hydroxymethylfurfural to 2,5-diformylfuran.

Iron oxide encapsulated by ruthenium hydroxyapatite as heterogeneous catalyst for the synthesis of 2,5-diformylfuran

Magnetic γ-Fe2 O3 nanocrystallites encapsulated by hydroxyapatite (HAP), HAP@γ-Fe2 O3 , were prepared followed by cation exchange of Ca(2+) on the external HAP surface with Ru(3+) to give the γ-Fe2 O3 @HAP-Ru catalyst. The structure of the as-prepared catalyst was characterized, and its catalytic activity was studied in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). γ-Fe2 O3 @HAP-Ru showed a high catalytic activity for the aerobic oxidation of HMF into 2,5-diformylfuran (DFF). A high DFF yield of 89.1 % with an HMF conversion of 100% was obtained after 4 h at 90 °C. Importantly, the synthesis of DFF from fructose was realized by two consecutive steps. The dehydration of fructose in the presence of a magnetic acid catalyst (Fe3 O4 @SiO2-SO3 H) produced HMF in a yield of 90.1%. Then the Fe3 O4 @SiO2 SO3 H catalyst was removed from the reaction solution with a permanent magnet, and HMF in the resulting solution was further oxidized to DFF with a yield of 79.1% based on fructose. The synthesis of DFF from fructose by two steps avoids the tedious separation of the intermediate HMF, which saves time and energy.

One-pot, one-step synthesis of 2,5-diformylfuran from carbohydrates over Mo-containing Keggin heteropolyacids

In this work, a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air is developed. H3 PMo12 O40 HPA is found to show high activity and selectivity to the formation of DFF owing to its higher Brønsted acidity and moderate redox potential. The partial substitution of the H(+) in H3 PMo12 O40 with Cs(+) leads to the heterogenization of the HPA by forming its cesium salts Csx H3-x PMo12 (x=0.5, 1.5, and 2.5). A satisfactory yield of 69.3% to DFF is obtained over Cs0.5 H2.5 PMo12 polyoxometalate after deliberate optimization of the reaction conditions. The heterogenized polyoxometalate could be recycled and reused without significant loss of catalytic activity for five runs. The produced DFF could be separated from the resulting mixture by an adsorption-desorption method using activated carbon as the adsorbent and furfural as the desorbent. A highest isolated yield of 58.2% is obtained.