The Preparation Of Metal-Organic Framework Membranes From Zinc Hydroxide Nanostrands And Their Properties

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials that have regular pore structure, high porosity and large surface area, and the diversity and adjustability of the structures and propersities, making their membranes be important candidates in gas separation, gas sensor and membrane catalysis. While, there are many difficulties in the preparation of MOF membranes, such as the difficulty of heterogeneous nucleation on support, high energy consumption, the use of expensive organic solvent, and the formation of defects and cracks. Therefore, we explore to develop a simple, effective, economical and environmental method to prepare MOF membranes using zinc hydroxide nanostructure as the unique precursor.The researches are as follows:1. Compact MOF-5 membranes are obtained using zinc hydroxide nanostructure as the precursor. Except for using as ligand, benzenedicarboxylic acid can also be used as capping reagents, and ZnO micro-hexagons with different morphologies are obtained, the growth and photoluminescence properties of which are studied.2. Well-intergrown ZIF-8 membranes with the thickness of about 800 nm are prepared directly from zinc hydroxide nanostrands without any modification of the substrate in ethanol-water at room temperature in a short time. Zinc hydroxide nanostructure also exhibits obvious structure-directing effect. This strategy has excellent versatility and is suitable for large-scale production.3. ZIF-8 membranes with better morphology and the thickness of about 2.5μm are obtained after secondary growth by using the ZIF-8 membranes from zinc hydroxide nanostrands. The single gas separation performance has been studied, and the ideal separation factors of H2/CO2, H2/N2 and H2/CH4are 3.58,12.53 and 9.76, far above Knudsen selectivity respectively, with the flux of H2 is 47.14*10-7 mol m-2 s-1 Pa-1. The performance also shows good reproducibility and durability.