Water-Based Synthesis of Zr6-Based Metal-Organic Framework Nanocrystals with Sulfonate Functions: Structural Features and Application to Fructose Dehydration

A series of zirconium-based metal-organic frame-work (MOF) nanocrystals (95-211 nm) displaying sulfonate functions (UiO-66-SO3H) was prepared in N,N-dimethylforma-mide (DMF)-the conventional solvent-and water, and their physicochemical properties were thoroughly investigated. In particular, X-ray diffraction results suggest that upon replacing DMF with water, the resulting MOF crystal structure presents a highly defective structure belonging to the space group Im3 of typical Fm3m. The acid catalysts were applied to the fructose dehydration into 5-hydroxymethylfurfural (5-HMF). Complete conversion of fructose over UiO-66-SO3H prepared in water was reached after only 30 min at 100 degrees C, in line with its stronger Bronsted acidity. In comparison, its counterpart prepared in DMF showed only 30% fructose conversion. Moreover, the intrinsic catalytic effect at 80 degrees C was only observed with the water-based UiO-66-SO3H. Without reactivation of the catalyst, recycling tests demonstrated the preservation of its structural integrity upon nine consecutive cycles, while a gradual loss of the catalyst activity was attributed to the humin adsorption on the MOFs.

Automated summary

In this study, a series of zirconium-based metal-organic framework (MOF) nanocrystals with sulfonate functions were prepared. The physicochemical properties of these nanocrystals were investigated, revealing that the MOF prepared using water instead of the conventional solvent DMF exhibited stronger Bronsted acidity and a highly defective structure. The water-based MOF nanocrystals showed higher catalytic activity and stability in the fructose conversion process.