Coupled acid and base UiO-66-type MOFs supported on g-C₃N₄ as a bi-functional catalyst for one-pot production of 5-HMF from glucose

Chemically functional microporous metal-organic frameworks (MOFs) crystals are attractive for catalysis applications, and recent results show that they can be immobilized on high stability substrates, such as carbon materials. In this work, g-C₃N₄ supported UiO-66-type MOFs catalysts with only acid, base or acid-base bi-functional active sites, have been successfully synthesized via a green (aqueous solutions), mild (90 °C, atmospheric pressure), and one-pot modulated hydrothermal (MHT) method. The physical and chemical properties of the obtained catalysts were systematically characterized by different characterization methods. The results indicated that the synthesized catalysts have microporous structure, excellent thermostability and acid-base bi-functional active sites. One-pot synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose was performed to investigate the activities of synthesized catalysts. Benefiting from the synergistic effects of the acid-base bi-functional active sites, the highest 5-HMF yield of 54.9% was achieved in an isopropanol-mediated DMSO system, under the optimal conditions. Moderate to excellent yields of 5-HMF were also obtained from one-pot conversions of other carbohydrates, including inulin, sucrose, cellobiose, maltose and starch, with our developed catalytic system. The one-pot production of 5-HMF from cellulose was also smoothly processed by the g-C₃N₄ supported UiO-66-type MOFs catalysts in an IL-based system. This work offers a versatile strategy for developing supported UiO-66-type MOFs catalyst for a wide range of biomass transformation to platform chemicals.