Direct production of 2,5-diformylfuran from fructose catalysed by Mo-based composite oxides in static air

One-Pot Effective Approach to 2,5-Diformylfuran From Carbohydrates Using MoS2-Decorated Carbonaceous Sugarcane Bagasse

Exploring the transformation of carbohydrates into valuable chemicals offers a promising and eco-friendly method for utilizing renewable biomass resources. Developing a bi-functional, sustainable heterogeneous catalyst is of utmost importance to attain a high level of selectivity for the desired product, 2,5-diformylfuran (DFF), in this direct conversion process. In this study, we developed a highly effective catalytic system to convert diverse carbohydrates into DFF. Our approach involved utilizing a MoS2 catalyst supported by amorphous carbon derived from sulfonated sugarcane biomass. The MoS2@SBG-SO3H composite was successfully synthesized using a facile and highly efficient method. The transformation of fructose into DFF achieved a significant yield of 70 % for 5 h at 160 °C using a one-step and one-pot reaction through dehydration and oxidation with oxygen. The oxidation of 5-hydroxymethylfurfural (HMF) into DFF using MoS2@SBG-SO3H was obtained at 94 % DFF within 5 h; the activation energy was 38.3 kJ . mol-1. The catalyst displayed convenient recovery and reusability. The direct synthesis of DFF from various carbohydrates, such as sucrose, glucose, maltose, and lactose, resulted in favorable yields. Our research provides a quick, green, and efficient process for preparing carbon-based solid acid catalysts and DFF.

Enhanced catalysis of a vanadium-substituted Keggin-type polyoxomolybdate supported on the M3O4/C (M = Fe or Co) surface enables efficient and recyclable oxidation of HMF to DFF

In the reaction of oxidizing 5-hydroxymethylfurfural (HMF), attaining high efficiency and selectivity in the conversion of HMF into DFF presents a challenge due to the possibility of forming multiple products. Polyoxometalates are considered highly active catalysts for HMF oxidation. However, the over-oxidation of products poses a challenge, leading to decreased purity and yield. In this work, metal-organic framework-derived Fe3O4/C and Co3O4/C were designed as carriers for the vanadium-substituted Keggin-type polyoxomolybdate H5PMo10V2O40·35H2O (PMo10V2). In this complex system, spinel oxides can effectively adsorb HMF molecules and cooperate with PMo10V2 to catalyze the aerobic oxidation of HMF. As a result, the as-prepared PMo10V2@Fe3O4/C and PMo10V2@Co3O4/C catalysts can achieve efficient conversion of HMF into DFF with almost 100% selectivity. Among them, PMo10V2@Fe3O4/C exhibits a higher conversion rate (99.1%) under milder reaction conditions (oxygen pressure of 0.8 MPa). Both catalysts exhibited exceptional stability and retained their activity and selectivity even after undergoing multiple cycles. Studies on mechanisms by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy revealed that the V5+ and Mo6+ in PMo10V2, together with the metal ions in the spinel oxides, act as active centers for the catalytic conversion of HMF. Therefore, it is proposed that PMo10V2 and M3O4/C (M = Fe, Co) cooperatively catalyze the transformation of HMF into DFF via a proton-coupled electron transfer mechanism. This study offers an innovative approach for designing highly selective and recyclable biomass oxidation catalysts.

Process coupling of CO2 reduction and 5-HMF oxidation mediated by defect-enriched layered double hydroxides

Aiming at the comprehensive utilization of waste carbon resources and renewable carbon resources, we put forward the photocatalytic coupling process of CO₂ reduction and 5-hydroxymethylfurfural (5-HMF) oxidation mediated by the anionic compound of layered double hydroxides (LDHs). Specifically, a ZnNiFe-LDH was synthesized by co-precipitation method, during which CO₂ was stored between LDH layers in the form of carbonate. Then, a certain amount of metal vacancies were introduced into LDH nanosheets by selectively etching Zn²⁺ ions. ICP-AES, EPR and XPS showed that the concentration of Zn vacancies gradually increased with the etching time prolonging, which thus optimized the electronic structure of LDH layers. Under the catalysis of the electron-rich metal cations and hydroxyl groups on the layers, the interlayer carbonate was in situ reduced into CO coupled accompanied with the 5-HMF oxidation to 2.5-furandiformaldehyde (DFF). Compared with the unetched ZnNiFe-LDHs, the CO and DFF yields over the LDHs etched for 3 h were increased by 2.84 and 2.82 times under UV-vis irradiation with a density of 500 mW cm^-2. Finally, combined with isotope-labeled ¹³CO₂ experiments and in situ FTIR characterization, we revealed the possible coupling mechanism and defect-induced performance enhancement mechanism.

Paired electrocatalysis in 5-hydroxymethylfurfural valorization

5-Hydroxymethylfurfural (HMF) has aroused considerable interest over the past years as an important biomass-derived platform molecule, yielding various value-added products. The conventional HMF conversion requires noble metal catalysts and harsh operating conditions. On the other hand, the electrocatalytic conversion of HMF has been considered as an environmentally benign alternative. However, its practical application is limited by low overall energy efficiency and incomplete conversion. Paired electrolysis and highly efficient electrocatalysts are two viable strategies to address these limitations. Herein, an overview of coupled electrocatalytic HMF hydrogenation or hydrogen evolution reaction (HER) with HMF oxidation as well as the associated electrocatalysts are reviewed and discussed. In this mini-review, a brief introduction of electrocatalytic HMF upgrading is given, followed by the recent advances and challenges of paired electrolysis with an emphasis on the integration HMF electrohydrogenation with HMF electrooxidation. Finally, a perspective for a future sustainable biomass upgrading community based on electrocatalysis is proposed.

Enhanced Basicity of MnOx-Supported Ru for the Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid

The present study focused on developing a stable basic MnOx support for Ru (RuMn) for the efficient oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) in water in the absence of an external base. A series of MnOx supports, synthesized via hydrothermal approach using urea as precipitant, was prepared by thermal treatment at various temperatures (300-800 °C) before doping with Ru. The RuMn-2 (1 wt % Ru, MnOx calcined at 400 °C) possessed a large number of basic sites (1.72 mmol g^-1 ) based on CO₂ temperature-programmed desorption analysis, affording an FDCA yield of 87 % with a turnover frequency of 22 h^-1 . Transmission electron microscopy energy-dispersive X-ray spectroscopy elemental mapping of RuMn-2 showed a high dispersion of Ru over the surface of MnOx, contributing to the efficient HMF oxidation. Moreover, X-ray diffraction, X-ray photoelectron spectroscopy, and H₂ temperature-programmed reduction indicated that the predominant MnO₂ phase (ϵ-MnO₂ ) played a vital role in HMF oxidation. RuMn-2 was recyclable for up to four runs without significant loss in the activity and retained its structural integrity.

Innovative Protocols in the Catalytic Oxidation of 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) has been identified as one of the most promising biomass-based multi-purpose platform molecules. Innovative protocols, namely electrocatalysis, photocatalysis, and microwave (MW)-assisted chemistry, as well as continuous-flow systems, add a new dimension and another promising toolbox for the oxidation of HMF in recent years. This Minireview deals with recent progress in the catalytic oxidation of HMF to 2,5-furandicarboxylic acid (FDCA) and other intermediates using noble, non-noble, and metal-free systems deploying emerging protocols. Selective HMF downstream oxidation products could be obtained not only via common catalyst modifications, namely nature of the metal, preparative method, and the property of deployed support, but also by using innovative processes.

Synthesis and characterization of an α-MoO3 nanobelt catalyst and its application in one-step conversion of fructose to 2,5-diformylfuran

α-MoO3 nanobelts have been successfully synthesized and applied as a bifunctional catalyst for one-step conversion of fructose to DFF under atmospheric air.