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^1,2,3. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation^4,5,6,7. 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.

金属有机骨架（MOF）是具有可设计拓扑，孔隙率和功能性的结晶多孔材料，在气体存储和分离，离子传导和催化^1,2,3中具有广阔的应用前景。由于透射电子显微镜（MOF）在电子束辐照下极度不稳定^{4,5,6,7，因此}用透射电子显微镜（TEM）观察MOF具有挑战性。在这里，我们使用直接检测电子计数相机以每平方英寸4.1超低剂量获取MOF ZIF-8的TEM图像，以保持结构完整性。所获得的图像涉及传输至2.1Å的结构信息，从而可以解析框架中Zn的单个原子柱和有机连接基。此外，TEM揭示了ZIF-8晶体的重要局部结构特征，这些特征不能通过衍射技术来识别，包括扶手椅型表面终端和已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晶体如何自组装以及界面腔对客体分子的质量传输的后续影响。