Investigating the catalytic influence of MIL-101(Cr) and MIL-101(Cr)-NH2 on glucose dehydration into 5-hydroxymethylfurfural and modelled through response surface methodology

Abstract

Dehydration of glucose into 5-hydroxymethylfurfural (5-HMF) is an effective approach for generating bio-based chemicals. Metal-organic frameworks (MOFs) are notable catalysts for this process due to their unsaturated metal centers. Functionalized MOFs further enhance these catalytic properties. This study investigates the catalytic abilities of MIL-101(Cr) and MIL-101(Cr)-NH₂ for glucose dehydration into 5-HMF using an H₂O + DMSO solvent system. Using Response Surface Methodology (RSM), the reaction parameters (temperature, time, and catalyst amount) were optimized to maximize 5-HMF yield. Results showed that at 180 °C, MIL-101(Cr) achieved a 5-HMF yield of 21 % with a selectivity of 22 %, while MIL-101(Cr)-NH₂ achieved a 5-HMF yield of 55 % with a selectivity of 56 %. MIL-101(Cr) demonstrated a glucose conversion rate of 92 %, and MIL-101(Cr)-NH₂ achieved a conversion rate of 99 % after 3 h at 180 °C. The optimized 5-HMF yield predicted by RSM for MIL-101(Cr) was 53.8 %, whereas the experimentally obtained value was 24.23 %. For MIL-101(Cr)-NH₂, the predicted 5-HMF yield was 35.46 %, with an experimental value of 47.51 %. The Lewis acidic nature of MIL-101(Cr) arises from the Cr sites, while MIL-101(Cr)-NH₂ exhibits both Lewis acidic characteristics from the Cr sites and Brønsted basic characteristics from the non-coordinated primary amine groups. The experimental results highlight the potential of MIL-101(Cr)-NH₂, which produced a higher 5-HMF yield compared to MIL-101(Cr). The dual nature of MIL-101(Cr)-NH₂ enhances glucose dehydration to 5-HMF, resulting in significantly higher yields. This study underscores the effectiveness of MIL-101(Cr)-NH₂ in converting glucose to 5-HMF, advancing biomass utilization efficiency.