Post-synthetic sulfonation of MIL-101(Cr) enabling high-performance fructose conversion to 5-HMF

Abstract

The design of structurally resilient and catalytically efficient solid acid materials remains a central challenge in biomass valorization. Herein, a sulfonated MIL-101(Cr)-SO₃H framework was constructed through a post-synthetic functionalization strategy, and its structural, textural, and thermal properties were comprehensively assessed. FT-IR and XRD analyses confirmed successful functionalization while preserving the crystalline architecture of MIL-101(Cr). SEM and elemental mapping analyses revealed uniform octahedral morphology with homogeneous distribution of Cr, C, O, N, and S, whereas N₂ sorption analysis showed a decrease in surface area from 2063 to 727 m² g⁻¹ due to partial pore occupancy by grafted organic groups. The catalyst exhibited high activity toward the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF), achieving a maximum yield of 98% under optimized conditions. Notably, the material retained its catalytic performance after four consecutive cycles with negligible loss of acidic sites and minimal structural alteration, as verified by post-reaction FT-IR and XRD analyses. Collectively, these findings establish MIL-101(Cr)-SO₃H as a highly robust and efficient solid acid catalyst for biomass-derived HMF production.