A supported membrane is provided comprising an inorganic, solid porous filtration membrane supported by an inorganic, solid porous support, said supported membrane comprising nanoparticles of a metal coordination polymer with CN ligands comprising Mn+ cations, where M is a transition metal and n is 2 or 3; and Alk+y[M′(CN)m]x− anions where Alk is an alkaline metal, y is 0, 1 or 2, M′ is a transition metal, x is 3 or 4, and m is 6 or 8; said Mn+ cations of the coordination polymer being bound through an organometallic or coordination bond to an organic group of an organic graft chemically attached to the surface of the filtration membrane, inside the pores of the filtration membrane, and optionally inside the pores of the support. The supported membrane may be used in a process for separating at least one metal cation and solid particles from a liquid medium containing the same.