巨大な開口部を有するキラル金属－有機ナノチューブの開発

多链化是金属有机框架（MOF）中常见的缠结模式之一，其中0D、1D或2D基序通过机械键连接以给出更高维度的框架。通常，多链MOFs中机械键的形成主要依赖于对微妙反应条件敏感的结晶过程。因此，拓扑结构的结果通常是难以预测的，和polycatenated MOFs的合成是相当偶然的，在这里，我们报告了一个更可控的方法来合成polycatenated MOFs，通过使用含有机械键的配体。机械互锁分子（MIM），如索烃和轮烷已被引入到MOFs中，但机械键仅作为配体的侧基。在这项工作中，四官能化的[2]索烃被设计为在每个大环上具有两个羧酸基团。当配体与合适的金属离子如Co（II）反应时，[2]索烃通过桨轮单元连接以产生3D框架，其中索烃的机械键形成骨架的一部分。这种链状骨架的MOF被发现能够感知微妙的环境变化，如温度和溶剂依赖性多态性所揭示的。更重要的是，发现该晶体是机械上最软的晶体。

Polycatenation is one of the commonly observed entanglement patterns in metal-organic frameworks (MOFs, where 0D, 1D or 2D motifs are connected through mechanical bonds to give a framework of a higher dimension. Usually the formation of mechanical bonds within polycatenated MOFs mainly rely on the crystallization process which is sensitive to subtle reaction conditions. As a result, the outcome of the topology is usually difficult to predict, and the synthesis of polycatenated MOFs is quite serendipitous.Here we report a more controlled method to synthesize polycatenated MOFs by using a ligand that contains a mechanical bond. Mechanically interlocked molecules (MIMs), such as catenanes and rotaxanes have been introduced into MOFs, but the mechanical bond only acts as the pendant of the ligand. In this work, a tetra-functionalized [2]catenane was designed to have two carboxylic acid groups on each macrocycle. When the ligand reacted with suitable metal ions such as Co(II), [2]catenanes are connected by paddlewheel units to produce a 3D framework with the mechanical bond of the catenanes forms a part of the backbone. This catenane-backboned MOF was found to be able to sense subtle environmental change, as revealed by the temperature- and solvent-dependent polymorphism. More importantly, the crystal was found to be a mechanically softest crystal.