ZIF-67@PDA/含氟聚酰亚胺混合基质膜的制备及其气体分离性能

Preparation of ZIF-67@PDA/fluorine-containing polyimide mixed matrix membrane and gas separation performance

金属有机框架材料(MOF)/聚合物混合基质膜(MMMs)通过结合MOF的分子筛效应和聚合物基质成本较低、加工性能好、机械强度高的特征,使其在气体分离领域展现出巨大的应用前景。然而由于MOF在聚合物基体中存在分散性差问题,极大地限制了其应用。采用溶剂热法合成金属框架材料ZIF-67,并通过溶液氧化法在ZIF-67表面修饰聚多巴胺(PDA)层制备ZIF-67@PDA纳米多孔材料。以4,4’-二氨基二苯醚-2,2’-双(3,4-二羧酸)六氟丙烷二酐(ODA-6 FDA)型含氟聚酰亚胺(FPI)为基体、ZIF-67和ZIF-67@PDA为填料,制备不同质量分数的ZIF-67/FPI和ZIF-67@PDA/FPI。通过FTIR、WAXD、TGA、SEM、比表面和孔径分布分析仪、气体渗透仪等测试对MMMs的结构和性能进行表征并测试了N_(2)、O_(2)、CO_(2)、He 4种气体的渗透性。结果表明:经聚多巴胺修饰后的纳米微孔材料ZIF-67在聚合物基体中能均匀分散并为气体分子的通过提供快速通道,且表现出良好的热稳定性。ZIF-67@PDA对CO_(2)具有良好的亲和性,这有利于提高CO_(2)/N_(2)选择性。当ZIF-67@PDA负载量为10wt%时,MMMs的CO_(2)渗透性和CO_(2)/N_(2)选择性协同增加,和纯FPI膜相比分别增加了131%、50%,MMMs表现出良好的气体分离性能。

Metal-organic framework(MOF)/polymer mixed matrix membranes(MMMs)have shown great promising application in gas separation fields by combining the features of MOF with molecular sieving effect and polymer matrix with lower cost,better processing properties,and high mechanical strength.However,their applications are greatly limited due to MOF poor dispersity in polymer matrix.The metal frame material ZIF-67 was synthesized by solvothermal method,and the polydopamine(PDA)layer was modified on the surface of ZIF-67 by solution oxidation to prepare ZIF-67@PDA nano-porous materials.The ZIF-67/FPI composite membrane and ZIF-67@PDA/FPI composite membrane with different mass fraction were prepared by using 4,4’-oxydianiline-2,2’-(hexafluoroisopropylidene)diphthalic anhydride(ODA-6FDA)fluorinated polyimide(FPI)as matrix and ZIF-67 and ZIF-67@PDA as fillers.The structure and properties of MMMs were characterized by FTIR,WAXD,TGA,SEM,specific surface and pore size distribution analyzer,gas permeant,and the permeability of four gases including N_(2),O_(2),CO_(2),and He was tested.The results show that the nanomicro porous material ZIF-67 modified with polydopamine can disperse uniformly in the polymer matrix and provides fast channels for the passage of gas molecules,and exhibits good thermal stability.ZIF-67@PDA has a good affinity for CO_(2),which is beneficial to improve the CO_(2)/N_(2)selectivity.When the ZIF-67@PDA loading is 10wt%,the CO_(2)permeability and CO_(2)/N_(2)selectivity of MMMs increases by 131%and 50%respectively compared with pure FPI membrane,and MMMs show good gas separation performance.