Crystallographic Visualization of Postsynthetic Nickel Clusters into Metal–Organic Framework

Postsynthetic metalation (PSM) has been employed as a robust method for the postsynthetic modification of metal–organic frameworks (MOFs). However, the lack of relevant information that can be obtained for the postsynthetically introduced metallic ions has hindered the development of PSM applications. Thanks to the advancement in single-crystal X-ray diffraction (SCXRD) technology, there have been a few recent examples in which successful postsynthetic introduction of single metal ions into MOFs occurred at the defined chelating sites. These works have provided useful explanations about the complicated host–guest chemistry involved in PSMs. On the other hand, there are only limited examples with crystallographic snapshots of the postsynthetic installation of metal clusters into the pores of MOFs using an ordinary SCXRD due to the loss of crystallinity of parent matrix during the PSM process. Herein, by the careful selection of starting materials and controlling the reaction conditions, we report the first crystallographic visualization of metal clusters inserted into Zr-based MOFs via PSM. The structural advantages of the parent Zr-MOF, which are inherited from the stable Zr6 cluster and triazole-containing dicarboxylate ligand, ensure both the preservation of high crystallinity and the presence of flexible coordination sites for PSM. Furthermore, PSM of metal clusters in a MOF pore space enhances stability of the final samples while also imparting the functionality of a successful catalyst toward ethylene dimerization reaction. The related construction ideas and structural information detailed in this work can help lay the foundation for further advancements using the postmodification of MOFs as well as open new doors for the utilization of SCXRD technology in the field of MOFs.后合成金属化 (Postsynthetic metalation, PSM) 已成为金属有机框架 (Metal–organic frameworks, MOFs) 后合成修饰的稳健方法。然而，由于无法获取后合成引入的金属离子的相关信息，PSM的应用发展受到了阻碍。得益于单晶X射线衍射 (Single-crystal X-ray diffraction, SCXRD) 技术的进步，近期已有少量研究实现了在特定螯合位点上将单金属离子后合成引入MOFs，这些工作为阐释PSM过程中涉及的复杂主客体化学提供了宝贵依据。另一方面，由于PSM过程中母体骨架的结晶性会发生丧失，使用常规SCXRD获取金属簇后合成装入MOFs孔道的晶体学快照的案例十分有限。本文通过精心选择起始原料并调控反应条件，首次通过PSM实现了金属簇嵌入锆基MOFs的晶体学可视化表征。母体Zr-MOF的结构优势源自其稳定的Zr₆簇与含三唑的二羧酸配体，这既保证了高结晶性得以保留，也为PSM提供了柔性配位位点。此外，在MOFs孔道内对金属簇进行PSM修饰，不仅提升了最终样品的稳定性，还赋予了其催化乙烯二聚反应的功能。本文详细阐述的相关构建思路与结构信息，可为MOFs后修饰领域的进一步发展奠定基础，同时也为SCXRD技术在MOFs领域的应用开辟了新方向。