| Membrane separation technology has unique advantages in chemical separation due to its advantages of simple operation,mild separation conditions,low energy consumption and high separation selectivity.Zeolitic imidazolate frameworks(ZIFs)as a new type of metal organic frameworks(MOFs),inheriting and developing the excellent porosity,chemical and physical stability of inorganic zeolite,which contributes ZIFs possess great application advantages in the separation of mixtures.This work designs membrane materials with different functions consist of ZIF-L or ZIF-8 for three kinds of mixtrues separation.The main research as follows.1.The two-dimensional ZIF-L crystallites with leaf-shaped morphology with a diameter of 6.3×2.54 ?m and a thickness of about 120 nm were prepared at room temperature.ZIF-L films with certain mechanical strength and different thicknesses were prepared on a nylon with a pore size of 220 nm by a simple vacuum filtration method.The Irregular structure of ZIF-L films formed by disordered stacked of ZIF-L crystals,which allowed ZIF-L films to achieve dyes removal with high selectivity under ultra-high flux.Membrane-based separation process can achieve highly efficient dyes removal in a short time and maintain high separation cycle stability compared with the adsorption of dyes by the same mass of ZIF-L crystals.The research provides a new ideal for developing an efficient and rapid membrane-based separation method for dyes removal.2.The ZIF-8 crystals with regular morphology and average size of about 200 nm were prepared at room temperature.The ZIF-8 nanocrystals were easily coated onto stainless steel meshes and a dense seed layer was formed under the action of polyethyleneimine(PEI).The ZIF-8 film coated stainless steel meshes were prepared by secondary growth method,and the pore size of the stainless steel mesh can be modulated by simply varying the crystallisation time.ZIF-8 film coated stainless steel meshes possess hydrophobicity in air and oleophobicity underwater,and its oleophobicity remains constant within a certain pore size range.The underwater oil contact angle of ZIF-8 film coated stainless steel mesh sharply increased from 148.3° to 159.5° when the pore size decreased from 16.9 to 14 ?m,which indicates that the ZIF-8 film coated meshes possess underwater superoleophobicity.Both immiscible and emulsified oil/water mixture can be efficiently separated with the separation efficiency respectively high up to 99.0%and 92.0%,and the flux up to 50 L m-2 s-1 and 380 L r-2 h-1 respectively.After 10 cycles,the separation efficiency and flux of ZIF-8 film coated meshes remains constant,which proves that the ZIF-8 film coated stainless steel meshes possess excellent stability and recyclability.This work lays a foundation for the development of MOF films for oil/water separation under practical working conditions.3.On the basis of previous studies,ZIF-8 seed layers with different densities have been prepared on the surface of alumina by evaporation-induced self-assembly(EISA)method,and then ZIF-8 membranes with diffirent thicknesses and orientations were fabricated by controlling the crystallization time.The SEM and XRD comfirm that the compactness and orientation improved with the increase of seed layer thickness and crystallization time.Highly c-oriented ZIF-8 membrane with a thickness of about 12.53 ?m and CPO(200)=0.84 is obtained after tertiary assembly and crystallizing for 4 h,the single gas permeation test confirmes that ZIF-8 membrane is defect-free.The separation performance of ZIF-8 membrane for H2/CO2 is improved with the increase of orientation,and it comfirms that there is a positive effect on gas sepatation performance to improve the membrane's orientation. |
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