New heteropolysiloxane (HPS) materials containing the 2,3,11,12-bis[4-(10-aminodecylcarbonyl)]-benzo-18-crown-6 and 2,3,11, 12-bis[4-(2-aminoethylcarbonyl)]-benzo-18-crown-6 compounds chemically linked in a reticulate silica matrix were synthesized by the sol-gel process. The preparation and the characterization of the HPS precursors are reported here. From these materials, dialysis membranes used for the facilitated competitive transport of silver/copper ions are obtained. The selectivity of the membranes is improved by the incorporation of the complexing molecules which allow a better solubility of silver ions in the membrane. In accordance with the experimental results, a dual transport mechanism is proposed, based on a reversible binding equilibrium solute/complexing site and a solute diffusion between two complexing sites.