Yunlei Zhang,Wen Guan,Hongyao Song,Yanan Wei,Pei Jin,Bing Li,Changhao Yan,Jianming Pan,Yongsheng Yan
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-C 3 N 4 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-C 3 N 4 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.
Despite that multi-modal hierarchically porous metal–organic frameworks (MOFs) are highly desirable due to their capability for the spatial organization of different host reaction, their facile synthesis templated by a single surfactant system is still challenging. Herein, we developed a temperature-controlled strategy to synthesize trimodal hierarchically porous Ce-based UiO-66-type MOFs (THPUiO(Ce)) with tailorable core–shell configurations by using nanoemulsions as soft templates. The hierarchical pore sizes and structures of cores and shells are controllable by facilely manipulating two-step temperatures and the components of the nanoemulsion. For a given nanoemulsion system, when the initial synthetic temperature is higher than the second one, the resultant THPUiO(Ce) is composed of dendritic channels (30–50 nm) in cores and smaller cage-like mesopores (15–20 nm) in shells. Reversely, when the initial synthetic temperature is lower than the second one, the smaller mesopores (around 15 nm) are located in cores surrounded by large pore channels. Similarly, trimodal hierarchically porous bimetallic THPUiO(Ce/Zr) can also be constructed upon extending this temperature-controlled approach, in which the molar ratio of the Zr content could be tuned up to 48%. In virtue of the inhomogeneous nature of THPUiO(Ce), the hollow Ce-based MOFs with mesopores distributed on 60 nm thickness shells can be achieved after the acid treatment of THPUiO(Ce). This facile assembly approach is expected to set a guideline for the construction of hierarchically porous MOFs for potential multicompartmental related applications.
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