Direct Transformation of HMF into 2,5-Diformylfuran and 2,5-Dihydroxymethylfuran without an External Oxidant or Reductant

In Situ Construction of N-Doped Ni3S2@Ni(OH)2 Self-Supported Heterostructures for Highly Selective Electrooxidation of 5-Hydroxymethylfurfural to 2,5-Diformylfuran

The selective electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) is promising for biomass valorization but remains challenging under alkaline conditions due to inefficient nonprecious metal catalysts. Herein, we develop a scalable N-doped Ni3S2@Ni(OH)2 heterostructure via a molten-salt-derived precursor and a one-pot hydrothermal synthesis. This catalyst achieves a low potential of 1.395 V (10 mA cm-2) and 96% DFF selectivity, with a 47.6% yield in 1.0 M K2CO3 (pH = 12). Experimental and DFT studies reveal that interfacial electron redistribution enhances HMF and hydroxyl radical adsorption, lowers the HMF-to-DFF energy barrier, and accelerates charge transfer. The hydroxyl group in HMF is more reactive than the aldehyde, boosting the DFF selectivity. The heterojunction's synergistic effect is key to achieving high-value aldehydes efficiently.

Recent advances in catalytic synthesis of 2,5-furandimethanol from 5-hydroxymethylfurfural and carbohydrates

5-Hydroxymethylfurfural (HMF) is a versatile platform chemical derived from the dehydration of renewable carbohydrates (typically glucose/fructose-based monosaccharides, oligosaccharides, and polysaccharides). Some useful compounds, such as 2,5-furandimethanol (FDM), 2,5-dimethylfuran (DMF) and 2,5-dimethyltetrahydrofuran (DMTHF), have been synthesized by reduction of HMF. Among these, FDM is a promising diol and can be further converted towards fine chemicals, liquid fuels and polymer materials. In this review, some typical catalytic systems for the synthesis of FDM from both HMF and carbohydrates were summarized. The discussion focused on controlling the reaction networks for the reduction of HMF. The reaction mechanisms and the stability of the catalysts were introduced briefly. Last but not least, the prospects of effective production of FDM were discussed as well.

A Diamine-Oriented Biorefinery Concept Using Ammonia and Raney Ni as a Multifaceted Catalyst

Diamines are important industrial chemicals. In this paper we outline the feasibility of lignocellulose as a source of diol-containing molecules. We also illustrate the possibility of turning these diols into their diamines in good to excellent yields. Central to these transformations is the use of commercially available Raney Ni. For diol formation, the Raney Ni engages in hydrogenation and often also demethoxylation, that way funneling multiple components to one single molecule. For diamine formation, Raney Ni catalyzes hydrogen-borrowing mediated diamination in the presence of NH₃.

Reductive Amination of 5-Hydroxymethylfurfural to 2,5-Bis(aminomethyl)furan over Alumina-Supported Ni-Based Catalytic Systems

Mono- and bimetallic Ni-based catalysts were prepared by screening 6 supports and 14 secondary metals for reductive amination of 5-hydroxymethylfurfural (5-HMF) into 2,5-bis(aminomethyl)furan (BAMF), among which γ-Al₂ O₃ and Mn were the best candidates. By further optimization of the reaction conditions at 0.4 g catalyst loading for 0.5 g substrate of 5-HMF and 160 °C of reaction temperature, 10Ni/γ-Al₂ O₃ and 10NiMn(4 : 1)/γ-Al₂ O₃ achieved the highest BAMF yields of 86.3 and 82.1 %, respectively. Although the BAMF yield values were comparable with that over Raney Ni, the turnover frequencies based on the initial BAMF yield and unit weight of Ni for 10NiMn(4 : 1)/γ-Al₂ O₃ , 10Ni/γ-Al₂ O₃ , and Raney Ni were calculated as 0.41, 0.09, and 0.04 h^-1 , respectively. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that the existence of MnO_x well dispersed on the γ-Al₂ O₃ support and its electron transfer effect with Ni particles on the surface of the support contributed to the high efficiency and better recyclability for the five-time reused 10NiMn(4 : 1)/γ-Al₂ O₃ catalyst.

One-Step Reductive Amination of 5-Hydroxymethylfurfural into 2,5-Bis(aminomethyl)furan over Raney Ni

Simultaneous reductive amination of C=O and C-OH in 5-hydroxymethylfurfural (HMF) into C-NH₂ in 2,5-bis(aminomethyl)furan (BAMF) is challenging. In this work, reductive amination of C=O in HMF was firstly studied, in which HMF can be converted into 5-hydroxymethyl furfurylamine (HMFA) with a 99.5 % yield over Raney Co catalyst. BAMF was then directly synthesized with 82.3 % yield from HMF over Raney Ni catalyst at 160 °C for 12 h. An even higher yield of 88.3 % could be obtained through a stepwise reductive amination process, in which the reaction started at 120 °C for the first 2 h over Raney Co mainly for amination of C=O and then continued at 160 °C for another 10 h over Raney Ni mainly for amination of C-OH. Under optimized reaction conditions, the catalyst could be reused four times without obvious loss in catalytic performance. XRD and XPS characterization of the reused catalyst indicated that the formation of Ni₃ N and the adsorption of alkyl amines could be the main reasons for the deactivation of the catalyst. Moreover, plausible reaction pathways were proposed to originate the detected by-products according to the kinetic profiles.

Taming the butterfly effect: modulating catalyst nanostructures for better selectivity control of the catalytic hydrogenation of biomass-derived furan platform chemicals

This minireview highlights versatile routes for catalyst nanostructure modulation for better hydrogenation selectivity control of typical biomass-derived furan platform chemicals to tame the butterfly effect on the catalytic selectivity.

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.

New AB type monomers from lignocellulosic biomass

A series of renewable novel bicyclic AB type polyester precursors have been prepared in good overall yield from lignocellulosic biomass. These advancements take full advantage of the differing oxidation states of functional groups in 5-(hydroxymethyl)furfural by chemoselective preparation of furanic hydroxy esters and applying benzyne-Diels–Alder cycloaddition/aromatization strategies.

Chemocatalytic Conversion of Cellulose into Key Platform Chemicals

Chemocatalytic transformation of lignocellulosic biomass to value-added chemicals has attracted global interest in order to build up sustainable societies. Cellulose, the first most abundant constituent of lignocellulosic biomass, has received extensive attention for its comprehensive utilization of resource, such as its catalytic conversion into high value-added chemicals and fuels (e.g., HMF, DMF, and isosorbide). However, the low reactivity of cellulose has prevented its use in chemical industry due to stable chemical structure and poor solubility in common solvents over the cellulose. Recently, homogeneous or heterogeneous catalysis for the conversion of cellulose has been expected to overcome this issue, because various types of pretreatment and homogeneous or heterogeneous catalysts can be designed and applied in a wide range of reaction conditions. In this review, we show the present situation and perspective of homogeneous or heterogeneous catalysis for the direct conversion of cellulose into useful platform chemicals.

Efficient conversion of 5-hydroxymethylfurfural to high-value chemicals by chemo- and bio-catalysis

5-hydroxymethylfurfural (HMF) is a very important versatile platform compound derived from renewable biomass.

The synthesis of HMF-based α-amino phosphonatesviaone-pot Kabachnik–Fields reaction

The first use of biomass-derived HMF in the one-pot Kabachnik–Fields reaction is reported here. A wide range of furan-based α-amino phosphonates were prepared in moderate to excellent yields under mild, effective and environmentally-benign conditions: iodine as a non-metal catalyst, biobased 2-MeTHF as the solvent and room or moderate temperature. The hydroxymethyl group of HMF persists in the Kabachnik–Fields products, widening the scope of further modification and derivatization compared to those arising from furfural. Issues involving the diastereoselectivity and double Kabachnik–Fields condensation were also faced.

A mild and efficient one-pot protocol for the synthesis of α-amino phosphonates directly from 5-HMF was described.

Direct conversion of carbohydrates to diol by the combination of niobic acid and a hydrophobic ruthenium catalyst

A variety of carbohydrates were converted to tetrahydro-2,5-furandimethanol in one step by the combination of Ru/SiO₂-TM and Nb₂O₅-FP.