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

聚catenation是金属有机框架（mof）中常见的纠缠模式之一，其中0D， 1D或2D基元通过机械键连接以获得更高维度的框架。通常，聚链化mof中机械键的形成主要依赖于结晶过程，而结晶过程对微妙的反应条件很敏感。因此，拓扑结构的结果通常是难以预测的，并且多catenated mof的合成相当偶然。在这里，我们报告了一种更可控的方法，通过使用含有机械键的配体来合成多catenated mof。机械互锁分子（mis），如连环烷和轮烷已被引入到mof中，但机械键仅作为配体的垂坠。在这项工作中，设计了一个四功能化[2]链烷，在每个大环上有两个羧基。当配体与合适的金属离子（如Co(II)）反应时，[2]链烷通过桨轮单元连接形成三维框架，链烷的机械键形成主链的一部分。这种以链烷为骨架的MOF能够感知细微的环境变化，正如温度和溶剂依赖性多态性所揭示的那样。更重要的是，这种晶体被发现是一种机械上最柔软的晶体。

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.