A novel zinc(II) metal-organic framework with a diamond-like structure: synthesis, study of thermal robustness and gas adsorption properties

A solvothermal reaction of Zn(II) salt with methanetetrabenzoic acid (H4MTB) and 1,4,8,11-tetraazacyclotetradecane (cyclam, CYC) created a new microporous metal-organic framework {[Zn-2(mu(4)-MTB)(kappa(4)-CYC)(2)]center dot 2DMF center dot 7H(2)O}(n) (DMF = N, N'-dimethylformamide). Single crystal X-ray diffraction showed that the complex exhibits a four-fold interpenetrated diamond-like structure topology with 1D jar-like channels with sizes about 14.1 x 14.1 and 2.4 x 2.4 angstrom(2). The stability of the framework and activation conditions of the compound have been studied by high-energy powder X-ray diffraction during in situ heating, thermogravimetric analysis coupled with mass spectrometry and infrared spectroscopy performed at different temperatures. The gas adsorption behaviour of {[Zn-2(mu(4)-MTB)(kappa(4)-CYC)(2)]center dot 2DMF center dot 7H(2)O}(n) was studied by adsorption of Ar, N-2, CO2 and H-2. Nitrogen and argon adsorption showed that the activated sample exhibits Brunauer-Emmet-Teller (BET) specific surface areas of 644 m(2) g(-1) (N-2) and 562 m(2) g(-1) (Ar). The complex adsorbs carbon dioxide with a maximum storage capacity of 10.5 wt% at 273 K and 101 kPa. The observed hydrogen uptake was 1.27 wt% at 77 K and 800 Torr, which is the highest value reported for the compounds containing a MTB4- linker. The adsorption heats of carbon dioxide and hydrogen, calculated according to the Clausius-Clapeyron equation, were in the range 22.8-22.4 kJ mol(-1) for CO2 and 8.9-3.2 kJ mol(-1) for H-2, indicating weak interactions of the gases with the framework.