Understanding the crystal structure of metal-organic framework thin film and the structural correlation with the underlying substrates

Metal-organic frameworks (MOFs) are nanoporous materials that are composed of metal ions connected with organic ligands leading to an ordered pore topology. Recently, we have developed a novel technique utilizing epitaxial substrates which promote in-plane nucleation and growth of 2D zeolitic imidazolate framework (ZIF) and succeeded in solving the structure of our 2DZIF film, which is different from its known 3D analog. We have extended the crystallization strategy to other promising MOFs (UiO-66-NH2, ZIF-7, CALF-20, MIL-53, MIL-101). Owing to the fact that MOFs are not stable under electron beam, we could not get the comprehensive understanding of 2D MOF structure including the in-plane and out-plane information. In particular, we are very interested in solving their crystal structure to understand the similarities and differences of the structure of 2D films and their 3D analog, and the correlation between orientation of 2D films and their underlying substrates.

金属有机框架（Metal-organic frameworks, MOFs）是一类由金属离子与有机配体连接构成的纳米多孔材料，具备有序的孔拓扑结构。近期，我们开发了一种利用外延衬底的新型制备技术，该技术可促进二维沸石咪唑酯骨架（2D zeolitic imidazolate framework, ZIF）的面内成核与生长，并成功解析了所制备的二维ZIF薄膜的晶体结构——该结构与其已知的三维同系物存在显著差异。我们已将该结晶策略拓展至其他具有应用前景的MOFs，包括UiO-66-NH₂、ZIF-7、CALF-20、MIL-53及MIL-101。由于MOFs在电子束辐照下不稳定，我们无法全面理解二维MOF的完整结构信息，包括面内与面外结构特征。尤为关键的是，我们亟需解析其晶体结构，以阐明二维薄膜与其对应三维同系物的结构异同，以及二维薄膜的取向与其基底衬底之间的内在关联。