A Stable Sulfonated Catalyst Derived From Amino-Functionalized MIL-53-NH2 for Efficient Fructose to 5-Hydroxymethylfurfural

The development of stable, efficient catalysts for fructose conversion to 5-hydroxymethylfurfural (5-HMF) remains a challenge. While sulfonation enhances Brønsted acidity in metal–organic frameworks (MOFs), it often compromises their structural integrity. This work addresses the critical challenge by demonstrating that amino (–NH 2 ) functionalization in MIL-53(Al) acts as a stabilizer, enabling the framework to withstand direct modification with chlorosulfonic acid and facilitating the introduction of sulfonic acid groups. The resulting sulfonated catalyst, MIL-53-N/S(1), achieves an outstanding 5-HMF yield of 84.3% in a biphasic system (170°C, 6 h). This work underscores the dual role of amino functionalization in stabilizing MOFs and enabling efficient acid catalysis for biomass conversion. Graphical A strategy using amino-functionalized MIL-53(Al) was proposed, where pre-grafted –NH 2 groups facilitate effective sulfonation to create abundant –SO 3 H sites without compromising framework stability. This approach addresses the challenge between acidity and structural degradation of MOFs. Under optimized conditions, MIL-53-N/S(1) achieves an HMF yield of 84.3%, demonstrating its potential for practical biomass valorization.