Metal-azolate framework-6s (MAF-6s) and their isomers: Preparation, modification, pyrolysis, and applications in adsorption and catalysis

Metal-azolate frameworks (MAFs), a sub-class of metal-organic frameworks (MOFs), are interesting porous materials thanks to high thermal/chemical stability and simple/facile design and synthesis. Among them, MAF-32, MAF-5, and MAF-6 are widely studied and isomeric MAFs with the composition of [Me(eim)₂]) (Me: usually Zn(II) or Co(II); Heim: 2-ethylimidazole). Although with the same composition, the three isomeric MAFs have different pore sizes and porosity; therefore, are interesting MOFs for basic studies. Moreover, MAFs, especially Zn-based ones, are very good precursors for porous carbon with or without some guest materials like metal oxides, nitrides, and carbides. Recently, those materials have been advanced much in the view of preparation, modification, pyrolysis, and applications. In this review, we will discuss the recent achievements, including applications in adsorption and catalysis, of the three MAFs and some relevant materials. Finally, a future outlook, together with a summary, will be provided for readers.