Crystalline microporous metal-organic frameworks (MOFs) are of a current interest in the field of crystal engineering and supramolecular chemistry due to their potential applications as catalysts, adsorbents, ion-exchangers and functional materials for hydrogen storage, carbon dioxide sequestration, and drug delivery. A strategy for the interpretation and design of such MOFs takes into account the shape of the molecular building blocks (MBBs) and represents nets as being sustained by vertex-linked polygons and polyhedra. In view of preparing new MOFs, we investigated the reactivity of Cu (I) and cyclic triimidazole (L=C9H6N6) [1] for its ability to act as as mono, di and tridentate ligand [2]. In particular, we observed that in situ partial reduction of Cu(NO3)2.6H2O in the presence of potassium iodide and L resulted in the {(CuI)3(L)4}n MOF with the (3,4)-connected topology. The compound crystallizes in the cubic space group F-43c (No 219), a= 21.4757(6) Å and V=9904.7(8) Å3. The porous cationic 3D network is built on the Cu (I) tetrahedra with nitrogen atoms in the vertexes (Fig., left) and possesses two types of cavities with diameters of ~5.4 Å and ~11 Å, respectively (taking in account the van der Waals radii of atoms of cavities walls), which provide the total potential solvent/anion accessible volume of 3959 Å3 (40%, Fig., center). The bigger cavities are interconnected by channels with diameter of at least 2.6 Å. The iodide anions are disordered in these cavities whose size is essentially bigger than the van der Waals radius of the iodine. The anion-exchange properties of this sieve-like network are in currently under investigation in our laboratories. Figure. View of the cubic 3D (3,4)-connected cationic MOF: molecular structure, solvent accessible surface, and topology represented as vertex connected tetrahedra and triangles.