Syntheses and Characterizations of Two 3D Cobalt−Organic Frameworks from 2D Honeycomb Building Blocks

The hydrothermal reaction of Co(NO3)2·6H2O, imidazole 4,5-dicarboxylic acid (H3IDC), and 4,4‘-bipydine (bipy) under different conditions affords two interesting metal−organic compounds, {[Co3(IDC)2(4,4‘-bipy)(H2O)4]·2H2O}n (1) and {[Co3(IDC)2(4,4‘-bipy)3]·6H2O·DMF}n (2), both of which have been structurally characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. Temperature-dependent magnetic susceptibility for 1 and 2 were also studied. The “all-chair” two-dimensional honeycomb networks, structurally analogous to CFx, were linked by the bridging 4,4‘-bipy ligand in compound 1 to give rise to a 2-fold interpenetrated 3D architecture. Compound 2 features a three-dimensional open framework with hexagonal channels, generated from two-dimensional graphene-like layers pillared by 4,4‘-bipy. The simplest cyclic motif of the 2D networks in 1 and 2 is a 24-membered hexagonal ring consisting of six Co(II) cations and six IDC3- trianions.