| Metal-organic framework materials（MOFs）are inorganic-organic hybrid material with large specific surface area,high porosity and polymetallic sites.They were widely used in adsorption,catalysis and separation.Among them,ZIF-8 had attracted wide attention due to their advantages,such as regular pore structure,good hydrothermal and chemical stability.Using ZIF-8 as the membrane material could combine the dual advantages of MOF and membrane.The preparation methods focused on the in-situ synthesis,secondary crystalline species,surface coupling agent method and homologous metal induction method.In particular,the homologous metal induction method had attracted much attention due to its high heterogeneous nucleation density.Generally,the homologous metal layer was usually introduced by electrochemical deposition and sol-gel method,resulting in the lack of binding force between the support and the homologous metal layer,further affect the stability of the synthesized MOFs membrane.Hollow fibers with the large specific surface area and high packing density as well as low cost become the most common membrane materials.In view of the above problems,the ZIF-8 membranes were directly induced and synthesized on the hollow fiber support.The ZIF-8 membranes were prepared on ZnO hollow fibers,ZnO-glass dust hollow fibers（ZnO-glass porous ceramic sheets）and ZnO-PESf organic hollow fibers.The effects of different conditions on the preparation of ZIF-8 membranes and gas permeability of the membrane were investigated,the main contents and results are as follows:1.Highly asymmetric ZnO hollow fibers were prepared by phase inversion/sintering technique,and ZIF-8 membranes were prepared by direct induction of supports.The influence of the sintering temperature on the morphology and structure of the hollow fiber was investigated.The porosity,average pore size and N2 permeation flux of ZnO hollow fibers were 62.6%,4.98μm and 4.26×10-4 mol·m-2·s-1·Pa-1at the sintering temperature of 1250℃.The effects of activation solution concentration,activation temperature,activation time,crystallization temperature,and crystallization time on the morphology,gas permeability,stability and repeatability of the ZIF-8membrane were investigated.When the concentration of the activation solution was 0.5mol·L-1,the activation temperature was 100℃,and the crystallization temperature was80℃,the ZIF-8 membranes with the thickness of 8.2μm were prepared.The gas permeation results showed that the permeation flux of H2 was 1.2×10-6 mol·m-2·s-1·Pa-1,and the ideal separation factors of H2/N2,H2/CO2,and H2/CH4 were 4.29,7.02,and3.73.The morphology and gas permeability of ZIF-8/ZnO hollow fiber composite membranes had no distinct change after ultrasonic and high temperature treatment.Under the same conditions,ZIF-8 membranes prepared in different batches had the considerable gas permeation.The results showed that the ZIF-8 membrane prepared by this method had excellent stability and repeatability.2.ZnO-glass dust hollow fibers doped with different mass fractions of glass dust were prepared by phase inversion/sintering technique.ZIF-8 membranes were prepared on the ZnO-glass dust hollow fibers.The influence of different glass dust doping amount on the structure of the hollow fiber was investigated.The porosity,average pore size and N2 permeation flux of ZnO-glass dust hollow fibers were 54.79%,1.58μm and2.24×10-5 mol·m-2·s-1·Pa-1at the glass dust content of 15%.The influence of different glass dust doping amount,activation temperature,activation time,crystallization temperature,and crystallization time on the morphology,gas permeability,stability and repeatability of the ZIF-8 membranes were investigated.When the amount of glass dust doped was 15%,the activation temperature was 80℃,and the crystallization temperature was 80℃,the ZIF-8 membranes with a thickness of 6.9μm were prepared.The gas permeation results showed that the H2 permeation flux were 9.67×10-7 mol·m-2·s-1·Pa-1,and the ideal separation factors of H2/N2,and H2/CO2 were 4.71,and 6.16.The morphology and gas permeability of ZIF-8 membranes had no distinct change after ultrasonic and high temperature treatment.Under the same conditions,ZIF-8membranes prepared in different batches had the considerable gas permeation.The results proved that ZIF-8/ZnO-glass dust hollow fiber composite membranes had excellent stability and preparation repeatability.3.The PESf organic hollow fibers doped with zinc oxide powder were prepared by phase inversion spinning technique,and ZIF-8 membranes with the continuous and flexible were prepared by direct induction.The influence of different doping amounts of zinc oxide on the hollow fibers,and the effects of different conditions on the morphology and permeability of ZIF-8 membranes were investigated.When the doping amount of ZnO was 10%,the activation temperature was 60℃,and the crystallization temperature was 60℃,the ZIF-8 membranes with a thickness of 6.2μm were prepared.The gas permeation results showed that the H2flux of ZIF-8 membranes was 1.06×10-7 mol·m-2·s-1·Pa-1,and the ideal separation factors of H2/N2,H2/CO2,and H2/CH4 were4.57,5.46,and 2.95,which reflecting excellent molecular sieving performance.The morphology and gas permeability of ZIF-8/ZnO-PESf composite membranes had no distinct after bending at 0-360°.Under the same conditions,ZIF-8 membranes prepared in different batches had the considerable gas permeation.The results showed that ZIF-8/ZnO-PESf composite membranes had excellent stability,flexibility,and preparation repeatability. |
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