Hierarchical Porous MIL-101(Cr) Solid Acid-Catalyzed Production of Value-Added Acetals from Biomass-Derived Furfural

Abstract

Considering economic and environmental impacts, catalytic biomass conversion to valuable compounds has attracted more and more attention. Of particular interest is furfural, a versatile biorefinery platform molecule used as a feedstock for the production of fuels and fine chemicals. In this study, the Cr-based metal-organic frameworks (MOFs) MIL-101 were modified by chlorosulfonic acid, and MIL-101 was changed into a hierarchical MOF structure with smaller particles and lower particle crystallinity by CTAB, which significantly improved the acidic sites of the MOFs. The original and modified MIL-101(Cr) catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TEM, and FT-IR. The effects of different catalysts, reaction temperature, catalyst amount, and alcohol type on the reaction were studied. Under the action of the MOFs catalyst, a new mild route for the condensation of furfural with various alkyl alcohols to the biofuel molecules (acetals) was proposed. The conversion route includes the conversion of furfural up to 91% yield of acetal could be obtained within 1 h solvent-free and in room-temperature reaction conditions. The sulfonic acid-functionalized MIL-101(Cr) is easy to recover and reuse, and can still maintain good catalytic activity after ten runs.

Advances in Metal-Organic Frameworks MIL-101(Cr)

“…The conversion of benzaldehyde catalyzed by MIL-101(Cr)-SO 3 H could reach 90%, which was much higher than that of MIL-101(Cr). MIL-101(Cr)-SO 3 H also showed pretty good catalytic activity for the acetalization of benzaldehyde with ethylene glycol, with 91% of yield in 1 h at room temperature [ 41 ]. Zhao et al [ 162 ] synthesized chitosan-coated MIL-101(Cr) nanoparticles, which exhibited excellent catalytic activity with the yield of 99% during a one-pot tandem deacetylation-knoevenagel condensation reaction (benzaldehyde dimethyl acetal releases methanol to produce benzaldehyde, and benzaldehyde undergoes synergistic dehydration with malononitrile to produce end product 2-benzylmethanecarbonitrile, Scheme 7 ).…”

Enhancing the middle frequency X-band electromagnetic wave absorbing through porous defect engineering on MoC x carbon hybrids and heat-insulating aerogel

“…Metal-organic frameworks (MOFs) with high speci c surface area, adjustable porosity and controllable chemical components have been employed as precursors for assemble high-performance composites and have been widely applied in gas adsorption separation, catalysis, bio-system, photoelectric conversion and energy storage [30][31][32][33]. In addition, there materials can be converted into transition metallic carbon-based composites through high-temperature pyrolysis, and their unique microstructures and porous characteristics can be maintained [34][35][36].…”

Quantification of the Microwave Effect in the Synthesis of 5-Hydroxymethylfurfural over Sulfonated MIL-101(Cr)

“…The acidic properties of some MOFs can, indeed, be further enhanced by adding functional groups such as nitro, sulfate, or phosphate to their structure to tune Brønsted and Lewis acid sites [68,69,[81][82][83][84]. The high activity and selectivity of sulfonated MOFs make -SO 3 H the 'functional group' of choice for these reactions [65,68,[84][85][86].…”

“…Robust functionalized MIL-101(Cr) with a Brønsted acid functional group, e.g., sulfonic MIL-101(Cr)-SO 3 H, made it superior to conventional solid acid catalysts such as acidic oxides, acid resins, phosphates, and zeolite-based catalysts [1,92,93]. MIL-101(Cr)-SO 3 H has shown good catalytic performance in converting fructose into 5-HMF [82,84,86]. Moreover, the sulfonated MIL-101 (Cr) has two excellent microwave-absorbing sites, i.e., the chromium and the sulfonic acid group [54,94].…”