The analysis of adsorption isotherms was based on the calculation of differential distributions of the amount adsorbed with respect to the adsorption potential.
It appears that the filling of Cu-BTC micro pores with nitrogen occurs in two steps due to specific interaction of nitrogen molecules with open metal sites. In contrast to nitrogen,the filling of Cu-BTC micro pores with argon takes place in one step.
The micro pores of Fe-BTC are filled with nitrogen and argon gradually in two featureless stages indicating the unordered porous structure.