Syntheses, Structures, and Gas Adsorption Properties of Two Novel Cadmium-Sodium Organic Frameworks with 1,3,5-Benzenetricarboxylate Ligands

Solvothermal reactions of Cd(CH3COO)(2)center dot 2H(2)O and NaOH with 1,3,5-benzenetricarboxylic acid (H3BTC) in a mixture of H2O/DMA (DMA = N,N'-dimethylacetamide) gave rise to two novel 3D porous metal-organic frameworks (MOFs), [Cd3Na6(BTC)(4)(H2O)(12)]center dot H2O (I) and [Cd3Na2(BTC)(3)(H2O)(3)]center dot[H2N(CH3)(2)]center dot H2O (2), which were characterized by single crystal and variable temperature powder X-ray diffraction (VTPXRD), IR spectroscopy, elemental analyses, inductively coupled plasma measurements, and coupled thermogravimetric-mass spectrometric analyses. Compound 1 crystallizes in the tetragonal space group P4(2)/n and could be described as a 2-fold interpenetrated net having a boracite (bor) topology, bridged by {Na3O12} trirners. Compound 2 crystallizes in the monoclinic space group Cc with ID channels distributed in an unusual honeycomb fashion along the b-axis. {Na2O10} dimers, (CH3)(2)NH2+ ions, and guest water are located in these channels. TG-MS and VTPXRD studies revealed that 1 had a high thermal stability up to 340 degrees C under air, and 2 was stable up to 310 degrees C. The gas-adsorption investigation disclosed that compound 1 exhibited H-2 uptake of 1.11 wt % at 77 K and 1.0 bar, with a high adsorption heat (8.4 kJ mol(-1)).