They have, on the other hand, relatively low stability under pressure. Like many members of the ZIF family, ZIF-8 is a very robust material compared to other metal-organic frameworks, with good chemical and thermal stability (up to 550☌). These cages are packed together to form the “sodalite” (or SOD) framework, from the name of the mineral where this topology was first encountered. The Zn(imidazolate)4 tetrahedra are organized together to form cages (called “sodalite cages”) with 8 hexagonal windows and 6 square windows. ZIF-8, the member of the family depicted above, has been one of the most studied.

For these reasons, the ZIFs are the largest family of metal-organic frameworks known to date, with more than 100 different topologies synthesized experimentally, and many more predicted from quantum chemistry calculations. ZIFs couple this extremely wide structural variability with the possibility to feature functionalized imidazolate linkers (present in metal-organic frameworks in general). This tetrahedral arrangement is equivalent to the zeolite structures, inorganic porous structures that have wide industrial applications, with more than 200 framework geometries known to date. Zeolitic imidazolate frameworks (ZIFs) are a family of metal–organic frameworks, consisting of imidazolate linkers bridging metal centers with tetrahedral coordination (Zn, Co, Cd, Li, B, …).

Picture generated with CrystalMaker ( ), from paper here: dx.doi.org/10.1039/c3cp54292k

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