Preparation Of MOFs/Fluorinated Polyimide Mixed Matrix Membranes And Study On Gas Separation Performance

Membrane separation technology has significant advantages such as environmental protection,low energy consumption,simple operation and low cost,which has attracted the attention of scientific researchers.Among the membrane separation materials,mixed matrix membrane materials（MMMs）have good processability of polymer membranes and superior gas permeability of inorganic membranes,which provides a new idea and method for the design and preparation of materials for membrane separation in the future.Therefore,in this thesis,novel fluorinated polyimide（FPI）,rare earth-organic framework Eu-MOF and zeolite imidazolate framework ZIF-67 were synthesized by molecular design.Then,three different MMMs were constructed using FPI as matrix,polydopamine（PDA）as coupling agent,Eu-MOF and ZIF-67 as dispersion fillers,and their applications in gas separation and fluorescence detection were explored.The main contents are as follows:1.The synthesized diamine monomer 2,2-bis（4-（4-amine phenylsulfone）phenyl）hexafluorpropane（BASA）and hexafluorodianhydride 6FDA were used to obtain FPI（6FDA-BASA）by"one-step method"high-temperature polycondensation.The organic ligand 2,4,5-triisopiperidine-1,3,5-triazine（H₃BTPCA）was prepared by solvothermal method,and Eu-MOF was synthesized by diffusion method.Then,PDA was modified on its surface by solution oxidation method to prepare Eu-MOF@PDA.Using 6FDA-BASA as matrix,Eu-MOF and its derivatives as fillers,MMMs（Eu-MOF/6FDA-BASA and Eu-MOF@PDA/6FDA-BASA）with different filler contents were prepared respectively.The interfacial compatibility,thermal stability,hydrophobic properties,ion fluorescence detection and gas separation properties of MMMs were systematically studied.The results show that MMMs have good thermal stability,interfacial compatibility,hydrophobic properties and gas separation properties,but also increase the permeability coefficient of He and CO₂ gas in MMM by57%and 64%,and the selectivity of He/N₂ and CO₂/N₂ increases by 8%and 14%respectively compared with 6FDA-BASA when the Eu-MOF@PDA addition amount is 6 wt%.At the same time,MMMs also have cation detection capabilities,among which MMM ion conjugate Fe³⁺-1 has obvious quenching effect,while Zn²⁺-1a luminescence is significantly enhanced.2.ZIF-67 was synthesized by solvothermal method,and then PDA was modified on the surface of ZIF-67 by solution oxidation method to prepare ZIF-67@PDA.Using FPI（6FDA-ODA）as matrix,ZIF-67 and its derivatives as filler,MMMs（ZIF-67/6FDA-ODA and ZIF-67@PDA/6FDA-ODA）with different filler contents were prepared respectively.ZIF-67 and its derivatives were characterized.And the thermal stability,interfacial compatibility and gas separation performance of MMMs were studied at the same time.The results show that ZIF-67@PDA has good dispersibility in the matrix.When the amount of ZIF-67@PDA added is 10 wt%,the CO₂ permeability and CO₂/N₂ selectivity of MMM were increased synergically,which were 131%and 50%higher than that of 6FDA-ODA,respectively,and showed its better gas separation performance.3.A novel diamine monomer 4-(3-Fluoro-4-（trifluoromethyl）-2,6-bis（4-aminophenyl）-pyridine（FTPPA）was designed and synthesized.The FTPPA and 6FDA were used through"one-step"polycondensation to obtain FPI（6FDA-FTPPA）.Subsequently,MMMs（ZIF-67@PDA/6FDA-FTPPA）with different filler contents were prepared by using ZIF-67@PDA as the filler.The structure and properties of 6FDA-FTPPA and its MMMs were characterized.The results showed that MMMs had high thermal stability(T_10%was above 500℃),good hydrophobicity（contact angle with water droplets was about 90°）and excellent interfacial compatibility（MMMs showed uniform and complete interfacial morphology with no obvious defects）.Compared with commercial 6FDA-ODA,6FDA-FTPPA showed superior CO₂/N₂ separation efficiency（CO₂/N₂ selectivity decreased by only6%when CO₂ gas permeability increased by 156%）.The gas permeability coefficient is greatest when the ZIF-67@PDA addition is 20 wt%,and the O₂ permeability and O₂/N₂ selectivity of this MMM coincide with the 1991 Robeson upper bound.