Preparation And Property Characterization Of Chiral Metal-Organic Frameworks Membranes

Chiral is a common phenomenon in nature. It is very important to achieve the separation of enantiomers especially in food and pharmaceutical industries as enantiomers may have different even opposite biological properties and pharmacological action. The existing technologies for enantiomer separation are commonly with low efficient, high energy consumption and expensive costing defects. It is extremely urgent to seek a new way to realize the enantiomer separation economically, efficiently, and environmentally.Membrane separation has all the advantages mentioned above. It has played an important role in water resource, energy and environment fields in our country, and it is a key component of the strategy to keep our economy development steady and sustaining. Metal-organic frameworks are a kind of new materials with predominant characteristics, such as permanent porosity, high surface area, structure controllable, easy modification, etc. They have been commonly used in catalysis, sensing, gas storage and separation fields. The successful synthesis of homochiral MOFs makes them possible for enantiomer separation. In recent years, ZIFs membranes have fulfilled the separation of small gases, in which ZIFs are a subclass of MOFs with relatively high stability. The quite mature membrane fabrication technology in inorganic membranes preparation serves so much for MOFs membrane fabrication.This essay’s main work was synthesizing proper seeds and fabricating chiral Ni-LAB membranes on α-Al2O3ceramic tubes through seeded secondary growth. Properties of the fabricated Ni-LAB membranes were characterized using scanning electron microscope, X-ray diffraction and single component gas permeability test.1. Some special investigations were focused on the influence of mother solution concentration, addition of surfactant Cetyltrimethyl Ammonium Bromide (CTAB) and pH value on the size and morphology of seeds. Seeds S37were chosen as the most suitable ones for membrane fabrication, which were made through reflux reaction with CTAB additive.2. A continuous Ni-LAB membrane was fabricated by the seeded secondary growth method on functional inorganic particles modified α-Al2O3ceramic tubes, in which the seeds were coated on the ceramic tube surface through vacuum-coating method, CTAB was added to the seed solution and Et3N was added to improve the activity of the mother solution. Property characterizations of the as-synthesized membranes were achieved by scanning electron microscope, X-ray diffraction and single component gas permeation test. The separation factors of the as-synthesized membrane are3.78,9.23and7.23for H2/N2, H2/SF6and H2/CO2respectively. The small gas molecules pass through the membrane conform to Knudsen diffusion, demonstrated that the Ni-LAB membrane was continuous without big defects.