Preparation Of Guest Assembly Metal-organic Frameworks Based Mixed Matrix Membranes For Olefin And Paraffin Separation

Mixed Matrix Membrane（MMM）is a kind of composite membrane materials assembled by filler materials and polymer matrix.It possesses both the improved permeability and selectivity compared with polymer membrane,thus has shown great potential in the field of membrane separation.As a new type of ordered porous crystalline material,Metal Organic Framework（MOF）has the characteristics of flexible and changeable ligands and metal nodes,high specific surface area,adjustable and modifiable pore structure,etc.MOF is expected to be applied in the fields of gas storage,separation,catalysis,fluorescent luminescence and energy technology.MOF materials show unique advantages in gas separation applications.Mixed matrix membranes based on MOFs show superior separation performance in many industrial gas purification processes.This thesis mainly aims to achieve the improvement of ethylene/ethane and propylene/propane separation performance of membrane materials by optimizing polymer materials and assembling guest of silver ions or phosphomolybdenum heteropolyacids into the MOF pores.The main research contents of this paper are as follows:（1）Performance optimization of polymer:The molecular weight and film-forming performance of polymer will affect the gas separation performance of mixed matrix membrane.By optimizing the purification process of monomers and the method of polymer synthesis,a self-contained microporous polymer（Polymers of Intrinsic Microporosity,PIM-1）with high molecular weight and good film-forming properties was synthesized,and a series of characterizations were carried out.The gas separation results show that the pure PIM-1 membrane after polymer optimization has excellent permeability and relatively low selectivity for C₂ and C₃,which provides a basis for the subsequent preparation of hybrid matrix membranes with excellent performance in composite MOF materials in PIM-1.（2）Assembly of silver ions:controllable structure and adjustable pore size are the great advantages of MOF when applied in the field of mixed matrix membranes.We select MOFs with different pore sizes to combine them with silver ion,and prepare mixed matrix membranes with PIM-1 by solution casting method to improve the alkane/olefins of the membrane materials.The gas permeation results show that Ui O-66-SO₃Ag crystals with small pore size as fillers can greatly increase the selectivity of the membrane material to alkanes/olefins,but exhibit a smaller gas flux,which is due to the assembled silver ions occupying pores of MOF material.The use of MIL-101-SO₃Ag with a larger pore size as a filler not only improves the selectivity of the mixed matrix membrane to alkanes/olefins,but also maintains its permeability at a relatively high level.With the pore environment engineering strategy,the preparation of high-performance MMMs was explored by selecting MOFs of different pore diameters for the assembly of silver ion guests as fillers,which provided a reference for the design and synthesis of high-performance gas separation membrane materials.（3）Assembly of phosphomolybdenum heteropoly acid:the polar interaction between heteropoly acid and alkene has a great influence on the separation of alkanes/alkenes.Based on the above principles,we try to quantitatively assemble phosphomolybdenum heteropolyacid into the MIL-101（Cr）channel with high stability,and use this as a filler to prepare high-performance MMMs that can effectively separate alkanes and olefins.The influence of the assembling ratio of phosphomolybdenum heteropolyacid in MOF materials and the doping ratio of MOF in MMMs on the properties of membrane materials alkane/alkene are the two focus of this chapter.The test results show that,compared with the pure PIM-1 membrane,the proper quantitative assembly of phosphomolybdic acid in the filler can enable the membrane material to maintain high permeability while increasing the alkane/olefin selectivity.Using the pore environment engineering strategy,the high stability MOF is assembled with phosphomolybdenum heteropoly acid guest as a filler to explore the preparation of high alkane/olefin separation performance MMMs,which provides a new idea for the design and preparation of high-performance alkane/olefin gas separation membrane materials.