Sonication-induced Ostwald ripening of ZIF-8 nanoparticles and formation of ZIF-8/polymer composite membranes

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• 作者：Joshua A. Thompson^a ; Karena W. Chapman^b ; William J. Koros^a ; Christopher W. Jones^a ; ^{cjones@chbe.gatech.edu} ; Sankar Nair^a ; ^{sankar.nair@chbe.gatech.edu}
• 关键词：Zeolitic imidazolate framework ; Mixed-matrix membranes ; Ostwald ripening ; Sonication ; Membrane formation
• 刊名：Microporous and Mesoporous Materials
• 出版年：2012
• 期刊代码：78_13871811
• 类别：ch
• 出版时间：1 August, 2012
• 卷：158
• 期：Complete
• 页码：292-299
• 文件大小：1261 K

摘要

The effect of typical membrane processing conditions on the structure, interfacial morphology, and gas separation performance of MOF/polymer nanocomposite membranes is investigated. In particular, the ZIF-8/Matrimid庐 nanocomposite membrane system is examined, and it is shown that ultrasonication - a commonly employed particle dispersion method - induces significant changes in the shape, size distribution, and structure of ZIF-8 particles suspended in an organic solvent during membrane processing. Dynamic light scattering and electron microscopy reveal that ZIF-8 nanoparticles undergo substantial Ostwald ripening when subjected to high intensity ultrasonication as often required in the formation of MOF/polymer nanocomposite membranes. Other characterization techniques reveal that the ripened particles exhibit lower pore volumes and lower surface areas compared to the as-made material. ZIF-8/Matrimid庐 composite membranes fabricated using two sonication methods show significant differences in microstructure. Permeation measurements show significant enhancement in permeability of CO₂ and increased CO₂/CH₄ selectivity in membranes fabricated with high-intensity sonication. In contrast, composite membranes prepared with low-intensity sonication are found to be defective. A careful evaluation of MOF membrane processing conditions, as well as knowledge of the properties of the MOF material after these membrane processing steps, are necessary to develop reliable processing-structure-property relations for MOF-containing membranes.