Preparation Of ZIF-67 Nanosheets Membrane And Study On Gas Separation Performance

Compared with traditional gas separation technology,membrane separation technology can achieve the selective separation of different gases according to the difference of the permeation rate of different gases.Meanwhile,membrane separation technology has the characteristics of low energy consumption,simple equipment,simple operation and low operation cost,making it a favorable competitor to replace traditional separation technology.Metal-organic frameworks(MOFs)have become one of the hot spots in the field of gas separation membranes in recent years because of its high specific surface area,adjustable pore size,flexible structure and good thermal stability.Zeolite imidazolate frameworks(ZIFs)is an important branch of MOFs materials,because of their similar spatial structures and bond angles with zeolite materials,has better chemical stability than other MOFs materials.In this study,ZIF-67 was selected as the membrane,alumina ceramic tube as the substrate,two-dimensional ZIF-67 nanosheets membrane was prepared via "bottom-up"strategy.Homologous metal hydroxide and different source metal oxides were used to prepare the ZIF-67 nanosheets membranes.The main contents are as follows:1.Silane coupling agent(3-aminopropyltriethoxy silane,APTES)was used to modify the porous alumina ceramic tube,and then Co(OH)2 nanosheets were directly grown on the modified substrate surface by hydrothermal method.Finally,ZIF-67 nanosheets membrane were prepared on the Co(OH)2 nanosheets layer modified substrate by solvothermal method.The influence of the reaction temperature,time and concentration of the synthesis solution on the microstructure of ZIF67 nanosheets was investigated in detail.The experimental results revealed that Co(OH)2 nanosheets layer could induce the preparation of continuous and dense ZIF-67 nanosheets membrane,the thickness of membrane is 470 nm.The H2 permeance of the prepared ZIF-67 nanosheets membrane was 1.918×10-8 mol·m-2·s1·Pa-1,and the H2/CO2 separation selectivity is 17.05.At the same time,the membrane can withstand high temperature to 120℃ and maintain high selectivity.2.The porous alumina ceramic tube without coupling agent modification was used as the substrate,the zinc sol was dip-coating on the inner surface of the ceramic tube,the ZnO nanoparticles layer was obtained by calcination,and the ZIF-67 nanosheets membrane was prepared on the ZnO modified substrate by solvothermal method.The experimental results showed that ZnO nanoparticles can induce the preparation of dense ZIF-67 nanosheets membrane,and the thickness of the membrane can be controlled by adjusting the concentration of synthetic solution.With the increase of the concentration of synthetic solution,the membrane thickness increased from 290 nm,to 530 nm.By optimizing the synthetic conditions,the H2 permeance of ZIF-67 nanosheets membrane of grow twice for 12 h was 2.684×10-8 mol·m-2·s-1·Pa-1,and the H2/CO2 separation selectivity was 21.04.The H2 permeance of ZIF-67 nanosheets membrane under the synthetic concentration of 1.5 U was 1.591×10-8 mol·m-2·s-1·Pa-1,and the H2/CO2 separation selectivity was 28.62,indicating that the prepared ZIF-67 nanosheets membrane exhibited good H2/CO2 separation performance.