Nanoporous membranes are made based on photoreactive hydrogen-bridged smectic liquid crystal dimers. The self-assembled layered structure is locked by photopolymerization. The hydrogen bridges are reversibly opened by heating or by changing the pH. This forms periodic pores of which the integrity is conserved by a covalent crosslinker, setting the spacing at ca. 1 nm. The pores are covered with carboxylic anions that bind to cations or to amines.