The Preparation And Gas Separation Properties Of PIM-1/GO/ZIF-8 Mixed Matrix Membranes

With the booming development of energy-intensive enterprises such as fossil fuel power plants and global warming caused by deforestation and other anthropogenic impacts on the environment,carbon capture technology has become an important part of energy saving and emission reduction programs in various countries around the world,and efficient gas separation technology has become increasingly important.Compared with traditional gas separation processes such as cryogenic liquefaction and solvent adsorption,membrane separation technology has outstanding advantages such as saving plant floor space,simplifying process operation procedures,enhancing gas capture efficiency,reducing industrialization costs,and enhancing process characteristics and functionality.PIM-1 is one of the most promising polymeric membrane materials for gas separation technology with high porosity,high free volume,and excellent gas molecule permeability,which has attracted much attention and discussion in the field of gas separation.In this paper,we focus on the influence of the regulation of the internal microstructure of polymers on the gas permeability and selectivity of gas separation membranes as well as the anti-aging properties,as follows:（1）In the first step of work,ZIF-8,a zinc-based metal organic skeleton,was used as the dispersed phase filler and PIM-1,a self-microporous polymer,was used as the continuous phase polymer matrix.PIM-1/ZIF-8 mixed matrix membranes（MMMs）casting solution with different mass percentages of ZIF-8 content was configured by direct melt blending method,and the mixed matrix membranes with different ratios were prepared by direct casting method.ZIF-8 has a high specific surface area and can expand a higher free volume in the PIM-1 polymer matrix,providing enhanced gas permeation performance for the hybrid matrix membranes;the pore size of the cage window of ZIF-8 matches the kinetic diameter of CO₂ gas molecules and exhibits excellent molecular sieving,resulting in a significant enhancement of the gas selectivity of the hybrid matrix membranes.The samples were fully and comprehensively characterized using FITR,¹H NMR,SEM,TGA,XRD,DSC and water contact angle,and the permeability of the sample membranes was systematically tested with a single gas CO₂ and N₂,respectively.The analysis of the results showed that among the mixed matrix membranes with different ratio loadings,the PIM-1/ZIF-8 mixed matrix membrane with 7 wt.%ZIF-8 loading had more excellent performance in various aspects,with a CO₂ permeability of 9275 Barrer and CO₂/N₂ selectivity of 25.（2）In the second work step,in order to solve the compatibility problem between filler and polymer,monolayer graphene oxide（GO）was used as the growth carrier of ZIF-8 to grow ZIF-8 in situ on GO substrate,and GO/ZIF-8 composite was prepared,and the PIM-1/GO/ZIF-8 cast film solution was prepared by direct solvation blending method,and the PIM-1/GO/ZIF-8 cast film was prepared by direct casting method.The loading of GO as ZIF-8 can improve the dispersion effect of ZIF-8 in the polymer matrix,while its great specific surface area significantly increases the free volume inside the hybrid matrix film,and the gas permeability is significantly enhanced;the numerous functional groups such as carboxyl and hydroxyl groups carried on its surface and edges have higher affinity for CO₂,which can bring more selectivity to the hybrid matrix film.superior selectivity.The results showed that the gas permeability and selectivity of the PIM-1/GO/ZIF-8 hybrid matrix membrane showed superior performance compared with the PIM-1/ZIF-8 hybrid matrix membrane,and the permeability of the PIM-1/GO/ZIF-8 hybrid matrix membrane with 9wt.%GO/ZIF-8 loading increased to 10937 Barrer for CO₂ single gas.The CO₂/N₂selectivity was also increased to 37,and the interfacial compatibility,thermal stability and anti-aging properties were also significantly improved.