Four 3D porous metal-organic frameworks with various layered and pillared motifs

Hydrothermal reactions of imidazole-4,5-dicarboxylic acid (H3IDC), 4,4'-bipyridine (bpy), and Cd(NO3)(2)center dot 4H(2)O under different conditions yielded four novel three-dimensional (3D) porous metal-organic frameworks (MOFs) of {[Cd-5(IDC)(2)(HIDC)(bpy)(3)(py)(2)(H2O)(3)] center dot 2NO(3) center dot 2H(2)O}(n) (1), [Cd-5(HIDC)(2)(IDC)(2)(py)(2)](n) (2), {[Cd-5(IDC)(3)(bpy)(2)(H2O)(2)] center dot NO3 center dot 3.5H(2)O}(n) (3), and {[KCd4(IDC)(2.5)(bpy)(2)(H2O)2] center dot 1.5NO(3) center dot 3H(2)O}(n) (4). X-ray single-crystal structural analyses revealed that IDC3- and HIDC2- in 1-4 exhibit six different types of coordination modes, among them two modes are first reported in this presentation. In 1 and 4, the cadmium ions are interconnected by mu(5)-IDC3- in two different asymmetrical coordination modes to produce two different infinite two-dimensional (2D) layers, which are further pillared by mu(2)-bpy (in 1) or mu(5)-IDC3- and mu(2)-bpy alternately (in 4) to form 3D porous MOFs of 1 and 4, in which the two asymmetrical coordination modes of mu(5)-IDC3- have not been reported. In 2 and 3, the cadmium ions are interconnected by mu(5)-IDC3- in a symmetrical coordination mode to form similar infinite 2D layers, and the 2D layers are further pillared by mu(4)-HIDC2- (in 2) or mu(4)-IDC3- and mu(2)-bpy alternately (in 3) to form 3D porous MOFs of 2 and 3. There are two different sizes of pores in 3 and 4, while the porous sizes are uniform in 1 and 2. Compounds 1, 2, and 4 display blue fluorescent emissions in the solid state at room temperature.