Preparation Of Metal-organic Framework/polymer Composite Membrane And Research On Its Gas Separation Performance

The effective reduction of harmful gas emissions,the large-scale fine separation of petrochemical and natural gas,and the efficient purification and utilization of high-quality clean energy gas such as hydrogen make gas separation become the key issue of environmental pollution control.As an efficient separation technology,membrane separation has attracted more and more attention.Metal organic framework material?MOF?has shown a huge application in gas separation.At present,the main substrate of MOF membrane is inorganic substrate,the production cost of inorganic substrate is high,which is not conducive to the large-scale industrial application of MOF membrane.Compared with inorganic substrate,polymer substrate has the advantages of low cost,good processability,various kinds and simple preparation process.Therefore,polymer substrate makes the industrial separation and application of MOF membrane have a better prospect,but the relevant research is relatively less at present.The purpose of this lesson is to explore the preparation method of high-performance MOF membrane based on polymer substrate,reduce the defects during the synthesis and activation process of MOF/polymer membrane,and improve the low connection strength between MOF layer and polymer substrate.The main research contents of this project are as follows:1. In view of the lack of crystal sites in the polymer substrate,we prepared the PSf?polysulfone?substrate with embedded ZIF-8 seeds by in situ synthesis,then fabricated the MOF membrane on the substrate by solvothermal method.On the one hand,these embedded particles acted as anchors to improve the bonding strength between ZIF-8layer and polymer substrate.On the other hand,these nanoparticles also provided crystal growth sites for polymer substrate,promoted the crystallization of ZIF-8 layer,reduced the crystallization time and avoided defects.The ZIF-8 membrane showed excellent mechanical strength and gas molecular sieve performance.2. In view of the insufficient of the first part of the study,which is the waste materials caused by the less effective seeds on the membrane surface and the lower effective utilization rate of MOF seeds,we deposited two-dimensional MOF?Zn₂?bim?₄?nanosheets on the surface of hydrolyzed polyacrylonitrile?PAN?substrate as seeds to achieve the maximum utilization of seeds.These crystals can be linked with the surface of polymer substrate by hydrogen bond,then the continuous and defect free MOF membrane can be prepared by L-b-L method.The membrane showed good gas separation performance.3. In view of the possibility that the natural brittleness of MOF leads to the defects of MOF membrane,and the problems of high gas transfer resistance and aging in the polymer intermediate layer of commercialized TFC membrane,a sandwich TFC membrane structure with MOF material as the intermediate layer of gas separation composite membrane and polymer functional layer MOF intermediate layer polymer substrate was designed.We prepared a TFC membrane with 2-D MOF gutter layer and ultra-thin cross-linked microporous polyacrylate?PAR?functional layer by interfacial polymerization.Due to the high gas permeability and stability of MOF interlayer,the membrane has excellent gas separation performance and long-term stability.This study is expected to provide a new approach to design high performance TFCMs for gas separation.