Mesoporous thin films containing organic functionalities behave like selective membranes. Titania mesoporous films with an accessible cubic mesostructure are deposited on a conductive electrode (see figure). Organic groups (phenyl, hexadecyl, glycerol) are added to the pore surface by post-grafting. The transport properties of electrochemical probes such as ferrocyanide or ferrocenedimethanol within the pore system depend on the grafted functionalities.