ChemInform Abstract: In situ Synthesis of Amide-imidate-imidazolate Ligand and Formation of Metal-Organic Frameworks: Application for Gas Storage

In this review article, we highlight the synthesis, structures and gas-sorption properties of a series of nine isostructural IFPs (IFP = Imidazolate Framework Potsdam) and two H-bonded networks. IFPs were synthesized by in situ partial hydrolysis of a 4,5-dicyanoimidazole under solvothermal conditions and hence an imidazolate-4-amide-5-imidate linker (C5H3N4O2) was generated, forming the metal–amide-imidate-imidazolateframeworks [M(C5H3N4O2)-R]. Varying R in the 2-substitued linker (R = Me, Cl, Br, Et, OMe and OEt) and metal centre (M2+ = zinc and cobalt) allowed the variation in channel diameter (4.2–0.3 A) and a fine-tuning of the polarity and functionality of the channel walls of IFPs. Furthermore, we show that using ethyl or alkoxy substituted IFPs the flexible groups act as molecular gates for guest molecules. This allows highly selective CO2 sorption over N2 and CH4 gases. Moreover, during the synthesis of methoxy substituted IFPs (IFP-7 and -8), an imidazolate-4,5-diamide-2-olate linker (C5H4N4O3) formed in situ leads to the formation of a molecular building block (MBB) with a M6 octahedron inscribed in a M8 cube (M = Zn2+ and Co2+). The MBBs connect by amide–amide hydrogen bonds to a 3D robust supramolecular networks [Zn14(C5H4N4O3)12(O) (OH)2(H2O)4 and Co14(C5H4N4O3)12(O) (OH)2(DMF)4 denoted as 1 and 2, respectively, DMF = N,N'-dimethylformamide], which can be activated for N2, CO2, CH4, and H2 gas-sorption.