MOFs are formed by the self-assembly of metal-ions, which act as coordination centre, bridged by organic ligands to form crystalline solids22. Due to the absence of non-accessible volume in MOFs, they have, on weight-speci?c basis, the highest porosity and surface area22. This leads to a high density of fully exposed active sites per volume. The topology of MOFs can be in?uenced by several parameters.
One factor is the preferred geometry of the metal-ions and linkers used for the synthesis35. Another important factor is the synthesis medium, which can interact with the framework during the synthesis. The solvent can play di?erent roles during the synthesis of MOFs, it can act as ligand, guest, both as ligand and guest and as a structure-directing agent36. The solvent can also a?ect the MOFs crystallinity, for instance, Bustamante et al.
investigated the crystallinity of ZIF-8 synthesised in di?erent alcohols. They found that the highest crystallinity of ZIF-8 was obtained in methanol and n-octanol. The lowest crystallinity was observed when 2-butanol was used for the synthesis37. One of the driving forces in the MOFs research is their potential use for many applications38, as they can bridge the gap between zeolites and enzymes10 and also can combine the bene?ts of both heterogeneous and homogeneous catalysis12. Nine-out-of-ten chemical processes make use of heterogeneous catalysts22. As mentioned in the introduction, MOFs can be tuned since di?erent metal-ions and organic linkers can be used for the synthesis.
Also combinations of di?erent metal-ions or linkers can be used, resulting in di?erent functionalities within the framework39. This makes it possible to design the MOFs with desired properties for di?erent applications40. The variety of MOFs that can be synthesised using di?erent linkers was shown by Eddaoudi et al. They synthesised a set of MOFs based on MOF-5 but with the presence of di?erent functional groups (such as halogens, hydroxyl and amino groups) or by changing the size of the organic linker41.