Reactions between the tritopic pyrazole-based ligand 1,3,5-tris(1H-pyrazol-4-yl)benzene (H3BTP) and transition metal acetate salts in DMF afford microporous pyrazolate-bridged metal–organic frameworks of the type M3(BTP)2*xsolvent (M = Ni (1), Cu, (2), Zn (3), Co (4)). Ab-initio X-ray powder diffraction methods were employed in determining the crystal structures of these compounds, revealing 1 and 2 to exhibit an expanded sodalite-like framework with accessible metal cation sites, while 3 and 4 possess tetragonal frameworks with hydrophobic surfaces and narrower channel diameters. Compounds 1–4 can be Desolvated without loss of crystallinity by heating under dynamic vacuum, giving rise to microporous solids with BET surface areas of 1650, 1860, 930 and 1027 m2/g, respectively. Thermogravimetric analyses and powder X-ray diffraction measurements demonstrate the exceptional thermal and chemical stability of these frameworks. In particular, 3 is stable to Heating in air up to at least 510 °C, while 1 is stable to heating in air to 430 °C, as well as to treatment with boiling aqueous solutions of pH 2 to 14 for two weeks. Unexpectedly, 2 and 3 are converted into new crystalline metal–organic frameworks upon heating in boiling water. With the combination of stability under extreme conditions, high surface area, and exposed metal sites, it is anticipated that 1 may open the way to testing metal–organic frameworks for catalytic processes that currently employ zeolites

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Reaction of Co(CF3SO3)2 with the new molecule 1,4-benzenedi(4'-pyrazolyl) (H2BDP) in N,N'-diethylformamide (DEF) at 130 degrees C generates the metal-organic framework Co(BDP).2DEF.H2O (1). X-ray analysis reveals the structure of 1 to contain chains of tetrahedrally ligated Co2+ ions linked through BDP2- ligands to generate a three-dimensional framework with 10 x 10 A2 channels. Thermogravimetric data shows the framework to have a high thermal stability, and complete desolvation occurs upon heating at 170 degrees C under dynamic vacuum for two days to afford 1d. X-ray powder diffraction data indicates that 1d possesses a substantially different structure, but converts back to 1 upon exposure to DEF, consistent with the presence of a flexible framework. Nitrogen adsorption isotherms measured for 1d at 77 and 87 K reveal an unprecedented five-step adsorption process and a Langmuir surface area of 2670 m2/g. In addition, high-pressure H2 adsorption data reveal hysteretic uptake and release, with hysteresis loops of width 1.1, 3.8, 13, and 27 bar that shift to higher pressures as the temperature increases from 50 to 65, 77, and 87 K, respectively. The high H2 uptake capacity of 5.5 excess wt % at 50 K suggests that such materials could potentially find utility for hydrogen storage via a kinetic trapping mechanism. Variable-temperature kinetics measurements have also allowed the first study of H2 diffusion within a metal-organic framework, revealing an energy barrier of 0.62 kJ/mol for H2 diffusing within the pores.