Zhu Yihan, Ciston Jim, Zheng Bin, Miao Xiaohe, Czarnik Cory, Pan Yichang, Sougrat Rachid, Lai Zhiping, Hsiung Chia-En, Yao Kexin, Pinnau Ingo, Pan Ming, Han Yu
King Abdullah University of Science and Technology (KAUST), Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division, Thuwal 23955-6900, Saudi Arabia.
National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Nat Mater. 2017 May;16(5):532-536. doi: 10.1038/nmat4852. Epub 2017 Feb 20.
Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how ZIF-8 crystals self-assemble and the subsequent influence of interfacial cavities on mass transport of guest molecules.
金属有机框架材料（MOFs）是具有可设计拓扑结构、孔隙率和功能的晶体多孔材料，在气体存储与分离、离子传导和催化领域有着广阔的应用前景。由于MOFs在电子束照射下极其不稳定，因此用透射电子显微镜（TEM）观察MOFs具有挑战性。在此，我们使用直接探测电子计数相机，以每平方埃4.1个电子的超低剂量获取MOF ZIF-8的TEM图像，以保持其结构完整性。所获得的图像包含了高达2.1埃的结构信息，能够分辨框架中锌原子列和有机连接体的单个原子列。此外，TEM揭示了ZIF-8晶体重要的局部结构特征，这些特征无法通过衍射技术识别，包括扶手椅型表面终止和组装晶体之间的相干界面。这些观察结果使我们能够了解ZIF-8晶体是如何自组装的，以及界面空腔对客体分子质量传输的后续影响。
