“…Moreover, Ramsahye et al have explained that the step-like isotherms in MIL-53 family of MOFs is a consequence of the very large framework flexibility and breathing effect of these solids [9], rather than any Coulombic effect. Obviously, this explanation cannot be applied to the rigid framework of Prior to the studies in MOFs, similar sigmoidal isotherms were observed for the adsorption of water in porous carbons, which have been explained as arising from cluster-like adsorption of water molecules around ''anchored'' water molecules which adsorb first onto hydrophilic defects, typical in such materials [10,11]. However, the presence of such ''anchoring'' defects is unlikely in MOF-5, and are totally absent in the computer modeling studies so far reported, where perfect lattices are used.…”