Novel Coordination Frameworks Based on Polytopic Heteroaromatic Nitrogen and Carboxylate Ligands

Metal-organic frameworks (MOFs) are comprised of metal clusters and organic ligands. MOFs, similar to zeolite, carbon nanotubes, and activated carbon, have very porous structures. Since MOFs have many more building blocks than materials such as zeolite, their properties can be finely tuned through a careful choice of the ligands. The functionalization of the MOF could be achieved by modifying ligands before the MOF synthesis (pre-synthetically) or after the synthesis (post-synthetically). These functionalized MOFs can be used for numerous applications such as gas storage, gas separation, and catalysis. The advantage of these hybrid materials, over classical (natural and synthetic) porous species (zeolites, active carbons, silica, etc.) resides in the possibility of easy optimization and fine tuning of their functional properties by using modification or substitution strategies of the organic ligands, and through the choice of suitable metallic ions [1, 2]. Moreover, the simultaneous presence of channels (or cavities) and metal ions capable of catalytic activity makes these materials particularly intriguing as heterogeneous catalysts for the transformation of small molecules, and, if the pores are suitably “decorated”, they can display significant size-, regio-, and enantioselectivity [3-6]. In this work we report the synthesis and characterization of a series of pyrazolylbased ligands, namely 3,3',5,5'-tetramethyl-1H,1'H-4,4'-bipyrazole (H2Me4BPz), 1H-pyrazole-3,4,5-tricarboxylic acid (H4PzTc), 1H,1'H-4,4'-bipyrazole (H2Pz) and their MOFs with late transition metals (Co2+, Ni2+, Zn2+, Cu2+, Ru++) characterized by the presence of diverse counterions.