Pillared-layer metal–organic frameworks (MOFs) are often encountered to “collapse” upon external stimuli due to weak interactions between the layers and the pillars. However, the detailed local structural change, especially the accumulation of defects due to intricately disordered bond dissociations, is not clear due to the complicated and dynamic nature of the collapse. We report a luminescent pillared-layer MOF structure, FDM-22, using zinc dicarboxylates as layers and dipyridyl ligands as pillars, in which three different transformed structures were captured along the increasing number of coordination bond dissociations between zinc metals and pyridine linkers. The transformation is triggered by these local point defect formations in the MOF, which further contribute to the modulation of its luminescence property, as well as prominent change in the morphology and pore distribution of the MOF. Evidenced by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), each of the pillar ligands has only one pyridyl group coordinated to a Zn(II) ion eventually, with the other uncoordinated pyridyl group pointing to the pore. With ∼10% of the coordination bonds breaking within the framework, FDM-22 provides a high concentration of active metal sites in the framework.

中文翻译：

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点缺陷累积引起的发光柱状层金属有机骨架的结构转变

由于金属层与支柱之间的相互作用较弱，经常会遇到柱状层金属有机框架（MOF）在外部刺激下“塌陷”的情况。然而，由于塌陷的复杂和动态性质，尚不清楚详细的局部结构变化，特别是由于错综复杂的键解离引起的缺陷积累。我们报告了发光的柱状层MOF结构FDM-22，使用二羧酸锌作为层和二吡啶基配体作为柱，其中沿着锌金属和吡啶连接基之间越来越多的配位键解离捕获了三个不同的转化结构。转换是由MOF中的这些局部缺陷形成触发的，这些缺陷进一步有助于其发光特性的调制，以及MOF的形态和孔分布的显着变化。通过拉曼光谱，X射线光电子能谱（XPS）和X射线吸收光谱（XAS）证明，每个柱状配体最终仅具有一个与Zn（II）离子配位的吡啶基，而另一个未配位的吡啶基指向毛孔。框架中约有10％的配位键断裂，FDM-22在框架中提供了高浓度的活性金属位点。