Isomerism is an essential and widespread phenomenon in organic chemistry but rarely observed in covalent organic frameworks (COFs), a novel class of crystalline porous organic polymers with versatile applications. Herein, we give an account of the first example of a controllable synthesis of constitutional isomers of a COF. The two isomers exhibited marked differences in their gas/vapor adsorption behaviors and chemical stability in various solvents. Furthermore, structure transformation from one isomer to the other was realized. This work not only paves the way for rational design and synthesis of COF isomers but also provides a vivid example of structure–property relationship in crystalline porous polymers.

中文翻译：

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共价有机框架中结构异构现象的研究：可控制的合成，转化和性质的不同

异构现象是有机化学中必不可少的普遍现象，但在共价有机骨架（COF）中却很少观察到，COF是一类具有广泛用途的新型结晶多孔有机聚合物。在此，我们给出了可控合成COF的结构异构体的第一个例子的说明。两种异构体在各种溶剂中的气体/蒸汽吸附行为和化学稳定性均表现出明显差异。此外，实现了从一种异构体到另一种异构体的结构转变。这项工作不仅为合理设计和合成COF异构体铺平了道路，而且为结晶多孔聚合物中结构与性质之间的关系提供了生动的例证。