Evaluation of an effective gas storage amount of latent nanoporous Cu-based metal-organic framework

The supercritical N-2, O-2, and CH4 adsorption isotherms on a Cu-based metal-organic framework, [Cu(4,4'-bipyridine) (2)(BF4)(2)](n), over the temperature range of 196-303 K were measured by a gravimetric method. The N-2 and O-2 adsorption isotherms at 196 K showed a vertical adsorption accompanied by a rectangular hysteresis loop. A method of evaluating the absolute adsorption amount of these gases was developed taking into account the intermolecular interactions for the buoyancy-mediated method. The isotherms of the absolute adsorption amount were obviously different from the isotherms of the surface-excess mass adsorption at 196 K. We also obtained isotherms of the absolute adsorption amount of CH4 at different temperatures. The isosteric heat of adsorption from the isotherms of the absolute adsorption amount of CH4 is larger than the liquefaction heat of CH4 at its boiling point by more than 3 kJ mol(-1).