Design of MIL-53(Al) with acidbase cooperative catalytic sites for the oriented conversion of cellulose

The valorization of cellulose into valuable platform chemicals necessitates efficient and sustainable catalytic systems, where the acid-base properties of catalysts are critical for directing reaction pathways. This work presents the one-pot synthesis of a series of aluminum-based metal-organic frameworks (MIL-53) with tunable acid-base functionalities, achieved by modulating organic linkers. The successful formation of cooperative acid-base sites was confirmed by comprehensive characterization, including X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and pyridine adsorbed infrared spectra. Catalytic performance evaluations demonstrated that acid-base cooperative sites significantly enhance the oriented conversion of cellulose to 5-hydroxymethylfurfural (5-HMF). Under optimal conditions (190 °C, 8 h) in a tetrahydrofuran (THF)/NaCl-H 2 O biphasic system, MIL-53-NH 2 /SO 3 H yielded 63.8 % 5-HMF, 6.3 % levulinic acid (LA), and 23.9 % formic acid (FA). The catalytic transformation of cellulose is a cascade process encompassing hydrolysis of cellulose to glucose, isomerization of glucose to fructose, dehydration to 5-HMF, and rehydration of 5-HMF to LA and FA. These results provide a promising strategy for designing efficient acid-base bifunctional catalysts for biomass conversion.