Isomerism in Metal–Organic Frameworks: “Framework Isomers”

Metal–organic frameworks (MOFs) are very important in the development of new technologies and study of gas storage and separation. MOFs are based on the complexation of metal clusters with organic ligands. Occasionally, the same building components combine in multiple different ways to produce different structures. These different structures are what we would call "framework isomers." This type of isomerism is unique to the field of MOFs. In this Perspective, we classify the different types of framework isomers and provide examples of each type. Additionally, we provide an analysis of the structure/property relationship. In addition, possible methods for future control over the synthesis of a particular framework isomer and characterization techniques have also been discussed.