Sun Yan, Zhu Yun, Zhang Shengmiao, Binks Bernard P
Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
Department of Chemistry, University of Hull, Hull HU6 7RX, U.K.
Langmuir. 2021 Jul 20;37(28):8435-8444. doi: 10.1021/acs.langmuir.1c00757. Epub 2021 Jul 8.
The shaping of metal-organic frameworks (MOFs), referring to the integration of small sub-millimeter MOF crystals into bulk samples of desired size and shape, is an important step in the practical use of this class of porous material in many applications. Herein, we demonstrate for the first time the fabrication of hierarchical 3D MOF monoliths within an MOF particle-stabilized high internal phase emulsion (HIPE). In this approach, a subfamily MOF (ZIF-8) is selected as the sole Pickering emulsion stabilizer for an oil-in-water (O/W) HIPE. With 2-methylimidazole and zinc nitrate in the continuous phase, ZIF-8 is formed in the emulsion to "bond" the ZIF-8 particles fabricating a ZIF-8 monolith without the addition of a polymer or polymerization of monomers. Freeze-drying of the HIPE produces a 3D ZIF-8 monolith. The monolith is packed into a chromatography column to test its catalytic performance as a flow-through catalyst in the Knoevenagel reaction. The monolith catalyst exhibits very high catalytic efficiency. Almost all the reaction mixture transforms to product within 2 min. Besides, the 3D ZIF-8 monolith showed excellent performance as an oil absorbent in oil-water separation. It achieved an absorption equilibrium of oil in less than 5 s, much faster than traditional high oil absorption materials.
金属有机框架材料（MOFs）的成型是指将亚毫米级的小MOF晶体整合到所需尺寸和形状的块状样品中，这是这类多孔材料在许多应用中实际使用的重要一步。在此，我们首次展示了在MOF颗粒稳定的高内相乳液（HIPE）中制备分级3D MOF整体材料。在这种方法中，选择一个亚族MOF（ZIF-8）作为水包油（O/W）HIPE的唯一Pickering乳液稳定剂。在连续相中加入2-甲基咪唑和硝酸锌，ZIF-8在乳液中形成，以“粘结”ZIF-8颗粒，从而在不添加聚合物或单体聚合的情况下制备ZIF-8整体材料。对HIPE进行冷冻干燥可得到3D ZIF-8整体材料。将该整体材料填充到色谱柱中，以测试其作为Knoevenagel反应中流通催化剂的催化性能。该整体材料催化剂表现出非常高的催化效率。几乎所有反应混合物在2分钟内都转化为产物。此外，3D ZIF-8整体材料在油水分离中作为吸油剂表现出优异的性能。它在不到5秒的时间内实现了油的吸收平衡，比传统的高吸油材料快得多。
