Synthesis of UiO-66-NH2(Ti/Zr) and its Catalytic Conversion of Cellulose to 5-HMF

UiO-66-NH2(Ti/Zr) modified by Ti metal oxide (TiO2) was used to catalyze the hydrolysis of cellulose to prepare 5-HMF. Under the optimal reaction conditions of H2O(NaCl)/THF(1/4 mL), 190 degrees C, 2 h and 50 mg UNT-3(Ti/Zr) (TiO2 and UiO-66-NH2 with mass of 1.5 and 0.1 g, respectively), the yield of 5-hydroxymethylfurfural reached 59.88%. UiO-66-NH2(Ti/Zr) nanocomposites with different mass ratios were successfully prepared by simple solvent evaporation method. SEM and TEM have shown that the modified UiO-66-NH2(Ti/Zr) are wrapped into sphere by TiO2 densely attached to the surface of UiO-66-NH2, which provides favorable conditions for the uniform dispersion of TiO2 and coordination of the Lewis acidic site of UiO-66-NH2. NH3-TPD results confirmed the existence of super-strong, strong, middle and weak acid sites in UiO-66-NH2(Ti/Zr), and Py-FTIR confirmed the existence of Bronsted and Lewis acids. After four cycles, the yield of 5-HMF and FUR decreased slightly from 59.88 to 51.89% and 9.11 to 7.66%, respectively, and the yield of 5-HMF could still remain above 50%. The results showed that the modified composite treatment of TiO2 with rich Lewis acid/base and UiO-66-NH2 could provide a certain idea for the extensive application of biomass research in the future.