Selective oxidation of 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid using silver oxide supported on calcium carbonate

Catalytic conversion of biomass-derived 5-hydroxymethylfurfural to 5-hydroxymethyl-2-furancarboxylic acid using novel cobalt-based MOF in the presence of deep eutectic solvents

The oxidation of 5-HMF to HMFCA is an important yet complex process, as it generates high-value chemical intermediates. Achieving this transformation efficiently requires the development of non-precious, highly active catalysts derived from renewable biomass sources. In this work, we introduce UoM-1 (UoM, University of Mazandaran), a novel cobalt-based metal-organic framework (Co-MOF) synthesized using a simple one-step ultrasonic irradiation method. The synthesis employed the ligand 4,4'-((1E,1'E)-((5-carboxy-1,3-phenylene)bis(azaneylylidene))bis (methaneylylidene))dibenzoic acid (H3bdda). A comprehensive suite of analytical techniques, including FT-IR, EDX, ICP, XRD, TEM, DLS, FESEM, and BET-BJH, was used to confirm the structural integrity of the synthesized material. The catalytic performance of UoM-1 was investigated for the selective conversion of HMF to HMFCA, demonstrating its effectiveness as a low-cost, accessible catalyst. To promote a more sustainable and environmentally friendly approach, the oxidation reactions were performed in deep eutectic solvents, which offer a green, low-energy alternative to traditional solvents. This study shows that the UoM-1 catalyst not only provides an economical solution but also aligns with modern green chemistry principles, making it a highly promising candidate for future catalytic applications.

Unveiling the Gold Facet Effect in Selective Oxidation of 5-Hydroxymethylfurfural and Hydrogen Production

Direct oxidation of 5-hydroxymethylfurfural (HMF) to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), crucial for medical supply production, is hindered by overoxidation. We synthesized gold nanomaterials with distinct single-crystal facets, {111} in octahedra (OC), {100} in nanocubes (NCs), and {110} in rhombic dodecahedra (RD), to investigate the facet-dependent HMF oxidation. The Au RD achieved the spontaneous oxidation of HMF to HMFCA with stoichiometric hydrogen production, maintaining 95% carbon balance, 91% yield, and 98% selectivity. In contrast, Au OC and NCs were inert. The superior performance is due to the absence of a C-H activation energy barrier on the Au(110) facet. Furthermore, gas chromatography and isotope experiments supported that the intermediate is oxidized to produce H2 via H- transfer, rather than H2O via H+ transfer. Oxygen was essential for scavenging electrons, thereby closing the reaction loop. The Au RD exhibited remarkable stability, operating for 240 h without performance degradation, indicating its potential for efficient HMFCA production.

Defective h-BNs-Supported Pd Nanoclusters: An Efficient Photocatalyst for Selective Oxidation of 5-Hydroxymethylfurfural

5-hydroxymethylfurfural (HMF) is one of the most promising biomass-based chemicals that is used to produce many kinds of important compounds. Especially, the selective conversion of HMF to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), an important chemical feedstock, has high industrial significance but is technically challenging. In this study, we present a high-performance photocatalyst for selective oxidation of HMF to HMFCA. By integrating an ultrasmall amount of palladium (Pd) nanoclusters (1.12‰ in weight) on defective hexagonal boron nitride nanosheets (Pd/defective h-BN nanosheets (dh-BNs)), outstanding photocatalytic performance can be achieved, resulting in up to a 95% HMF conversion ratio with an 82% HMFCA selectivity. The performance is considerably higher than that of pristine dh-BNs and Pd on defect-free h-BNs. More importantly, this Pd/dh-BNs catalyst maintains a high catalytic activity after eight cycles, demonstrating robust catalytic stability. Density functional theory calculations indicate that Pd/dh-BNs can lower the energy barrier for HMF oxidation and facilitate the desorption of HMFCA, which contributes to the high selectivity catalytic performance. This study not only introduces a promising photocatalyst for sustainable chemical transformations but can also provide valuable insights into the design of advanced photocatalytic material for biorefinery applications.

5-Hydroxymethylfurfural and its Downstream Chemicals: A Review of Catalytic Routes

Biomass assumes an increasingly vital role in the realm of renewable energy and sustainable development due to its abundant availability, renewability, and minimal environmental impact. Within this context, 5-hydroxymethylfurfural (HMF), derived from sugar dehydration, stands out as a critical bio-derived product. It serves as a pivotal multifunctional platform compound, integral in synthesizing various vital chemicals, including furan-based polymers, fine chemicals, and biofuels. The high reactivity of HMF, attributed to its highly active aldehyde, hydroxyl, and furan ring, underscores the challenge of selectively regulating its conversion to obtain the desired products. This review highlights the research progress on efficient catalytic systems for HMF synthesis, oxidation, reduction, and etherification. Additionally, it outlines the techno-economic analysis (TEA) and prospective research directions for the production of furan-based chemicals. Despite significant progress in catalysis research, and certain process routes demonstrating substantial economics, with key indicators surpassing petroleum-based products, a gap persists between fundamental research and large-scale industrialization. This is due to the lack of comprehensive engineering research on bio-based chemicals, making the commercialization process a distant goal. These findings provide valuable insights for further development of this field.

Preparation of carbon-supported ruthenium spinel oxide catalyst and application thereof in the oxidation of 5-hydroxymethylfurfural

Trivalent ruthenium (Ru) can catalyse the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). However, the structure of Ru itself is unstable and is prone to aggregation and oxidation, leading to a decrease in catalytic activity. Therefore, it is necessary to prepare a stable, reliable, Ru-based catalyst. Based on the catalytic properties of trivalent Ru, a stable spinel structure with zinc ferrite was designed and loaded onto different carbon supports to prepare a homogeneous and stable Ru-based catalyst. The structure and physico-chemical properties were characterized through scanning electron microscopy, X-ray diffraction, transmission electron microscopy and other techniques, and the catalyst was applied to the oxidation of HMF for the preparation of FDCA. The results show that the prepared magnetic activated carbon-supported Ru-based catalyst has a concentrated particle size distribution in the range of 5-8 nm, with a loading amount of 3.61 at%. It exhibits strong soft magnetism, which is beneficial for Ru loading. Additionally, it can be reused in the oxidation of HMF to prepare FDCA over 10 cycles, with the product yield remaining essentially unchanged. The catalyst prepared in this study is characterized by recyclability and structural stability, making it promising for practical applications.

Photocatalysis of Cr- and Fe-Doped CeO2 Nanoparticles to Selective Oxidation of 5-Hydroxymethylfurfural

Oxygen vacancies (V_o) present in CeO₂ nanoparticles (NPs) can effectively boost their photocatalytic activity under ultraviolet (UV) light. To improve photocatalytic performance, Cr- and Fe-doped CeO₂ NPs with increased V_o were prepared using a simple method of doping Cr and Fe ions into CeO₂ NPs, which was confirmed by an in-depth analysis of the structural and electronic changes. Through photocatalytic degradation (PCD) experiments with 5-hydroxymethylfurfural (HMF), we found that the PCD rates of the two doped CeO₂ NPs were faster than that of the CeO₂ NPs. In addition, the conversion of HMF to 2,5-furandicarboxylic acid (FDCA) using the doped CeO₂ NPs occurred only through the mechanism of the selective oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), exhibiting better efficiency than using CeO₂ NPs.

5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid on Noble Metal-Free Nanocrystalline Mixed Oxide Catalysts

Noble metal-free catalysts based on earth-abundant and inexpensive mixed oxides are active catalysts of all steps of the reaction cascade leading from 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) using tert-butyl hydroperoxide (TBHP) as oxidation agent. Catalysts covering the whole range of composition in the Cu-Mn and Co-Fe series have been prepared and characterised. The nature and composition of the catalyst strongly affect conversion and selectivity. The distribution of products indicates that radical-type oxygen species, deriving from the activation of TBHP, play a determining role in the reaction. The early steps of reaction mainly follow the pattern expected for heterogeneous Fenton catalysts. Mixed oxide catalysts are the most effective in further oxidation steps, leading to the formation of FDCA, both in the Cu-Mn and Co-Fe systems. This behaviour can be related to the distribution of charge in the mixed oxides, suggesting a possible implication of the lattice oxygen in the last reaction steps. The results provide indications on how to optimize the reaction and minimize the formation of byproducts (humins and oligomers).

Enabling Efficient Aerobic 5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid in Water by Interfacial Engineering Reinforced Cu-Mn Oxides Hollow Nanofiber

Herein, a one-dimensional hollow nanofiber catalyst composed of tightly packed multiphase metal oxides of Mn₂ O₃ and Cu_1.4 Mn_1.6 O₄ was constructed by electrospinning and tailored thermal treatment procedure. The characterization results comprehensively confirmed the special morphology and composition of various comparative catalysts. This strategy endowed the catalyst with abundant interfacial characteristics of components Mn₂ O₃ and Cu_1.4 Mn_1.6 O₄ nanocrystal. Impressively, the tuning thermal treatment resulted in tailored Cu^I sites and surface oxygen species of the catalyst, thus affording optimized oxygen vacancies for reinforced oxygen adsorption, while the concomitant enhanced lattice oxygen activity in the constructed composite catalyst ensured the higher catalytic oxidation ability. More importantly, the regulated proportion of oxygen vacancy and lattice oxygen in the composite catalyst was obtained in the best catalyst, beneficial to accelerate the reaction cycle. Compared to other counterparts obtained by different temperatures, the CMO-500 sample exhibited superior selective aerobic 5-hydroxymethylfurfural (HMF) oxidation to 2,5-furandicarboxylic acid (FDCA, 96 % yield) in alkali-bearing aqueous solution using O₂ at 120 °C, which resulted from the above-mentioned composition optimization and interfacial engineering reinforced surface oxygen consumption and regeneration cycle. The reaction mechanism was further proposed to uncover the lattice oxygen and oxygen vacancy participating HMF conversion process.

Highly efficient catalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid using bimetallic Pt-Cu alloy nanoparticles as catalysts

Bimetallic platinum-copper alloy nanoparticles are highly active catalysts for the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) under base-free conditions, with a high turnover frequency of up to 135 h^-1 in aqueous solution. The Pt-Cu_1.5/AC alloyed catalyst promoted the rate-determining step in the tandem oxidation compared with the monometallic Pt/AC catalyst, thus improving the catalytic performance.