The Research On The Modification Of Metal-Organic Framework ZIF-8 And PVDF Membranes

Metal-Organic Framewok?MOFs?represents a new class of porous nanostructured materials constructed from organic ligands and inorganic metal nodes.Its unique structural characteristics make it suitable for photovoltaic materials,catalysis,separation,and storage which has broad application prospects in the future.At present,the research hotspots of MOFs not only focus on the preparation of novel structures,but also have expanded to explore their structure-activity relationship and practical applications.Polyvinylidene fluoride?PVDF?is one of the most widely used polymers in the world,and has been widely used in microfiltration,ultrafiltration and other fields.With the development of science and technology,industrial requirements for membrane separation efficiency have become higher and higher.Therefore,the search for better membrane materials and more efficient separation and catalysis methods has become a research hotspot.Studies have reported that the combination of MOFs and porous membranes is also an effective method to improve the permeability and separation performance of separation membranes.In this article,PVDF and MOFs are combined to prepare ZIF-8 crystal membranes with photocatalytic performance,new ZIF-8-PVDF composites with CO₂ adsorption capacity,and ZIF-8/PVDF ultrafiltration membrane for dye wastewater treatment.,the specific research contents are as follows:?1?A ZIF-8 crystal membrane was prepared by a secondary growth method,using filter paper as a growth support for the ZIF-8 crystal membrane,2-methylimidazole?HMIm?as an organic ligand,zinc nitrate hexahydrate[Zn?NO₃?₂·6?H₂O?] as a source of metal ions,and PVDF as a slow release agent for organic ligands.The structures and properties of the prepared ZIF-8 crystals and a ZIF-8 crystal membrane were characterized by SEM,XRD and photocatalysis.Studies have shown that the porous structure of filter paper has an effect on the crystallization process of crystals in the first synthesis.Among them,some groups of cellulose constituting the filter paper participate in the coordination action of HMIm and Zn²⁺,thereby changing the final morphology of the crystal formation-regular hexagons,and the crystals also tend to grow continuously from the dispersed single crystals.The photocatalytic efficiency of a ZIF-8 crystal membrane for methyl orange solution is basically maintained at about 70 %,while the photocatalytic efficiency of methyl orange solution itself is 16.82 %.Therefore,the ZIF-8 crystal membrane has certain photocatalytic performance.And the research paved the way for the study of the crystal morphology of MOFs.?2?A novel of ZIF-8-PVDF composite material was prepared by the auxiliary solvothermal method?PAS?.The effects of different contents of PVDF on the morphology and properties of ZIF-8-PVDF composite material were comprehensively studied.The chemical composition,structure and properties of the obtained ZIF-8-PVDF composite material were characterized by FT-IR,XRD,SEM and BET.The results show that the novel ZIF-8-PVDF composite material not only has interesting crystal morphology,from diamond dodecahedron with protrusions to the final hexagonal morphology,but also has a large specific surface area.Compared with ZIF-8,the pore size distribution of the novel ZIF-8-PVDF composite material falls within the range of mesopores,which greatly improves its application potential in the field of adsorption.When the PVDF content is a minimum of 0.5 g,its carbon dioxide?CO₂? adsorption capacity is the smallest;as the PVDF content increases,the CO₂ adsorption capacity also increases.?3?A ZIF-8/PVDF ultrafiltration membrane for dye wastewater treatment was prepared by in situ growth method at room temperature by adding the organic ligand HMIm of ZIF-8 into the casting membrane solution,and adding the metal ion Zn?NO₃?₂·6?H₂O?of ZIF-8 into the gel bath.And the prepared membrane was immersed into the gel bath to realize the synthesis of ZIF-8,thereby realizing the preparation of ZIF-8/PVDF ultrafiltration membrane.By FT-IR,XRD,SEM and Evans blue dye wastewater treatment were used to characterize the morphology,chemical composition and properties of the ZIF-8/PVDF ultrafiltration membrane.Studies have shown that ZIF-8 was synthesized in a gel bath by in situ growth method,and ZIF-8 was present on the surface and in the membrane.Compared with PVDF pure membrane,the rejection rate of Evans blue dye was significantly improved.When the content of HMIm is 8 g,the rejection rate of the ZIF-8/PVDF ultrafiltration membrane to the dye Evans blue is 96.17 %,and the rejection rate to the OVA salt solution is 97.37 %.The pure water flux is 180 L·m^-2·h^-1.As the quality of HMIm increases,the content of ZIF-8 also increases.When the HMIm content was 12 g,the water flux was significantly increased to 208.5 L·m^-2·h^-1,the rejection rate to Evans blue dye was 97.17 %,and the rejection rate to OVA salt solution is 99.06 %.To sum up: ZIF-8/PVDF ultrafiltration membrane has good separation performance and anti-pollution performance.