A multiply fused, conjugated, porphyrin polymer film coated on a substrate, wherein the porphyrin monomer repeating units are di-meso-substituted porphyrins; and including a metal cation selected from the group consisting of Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(II), Pd(II), Ag(II), Pt(II) and Au(III), or mixtures thereof; the porphyrin units are multiply fused, including doubly-fused and/or triply-fused; including a substituent R attached to the meso position of the porphyrin monomer, the substituent R being an aromatic group presenting at least one free ortho position among; at least one of the two free ortho positions of the aromatic substituent is fused to the 13 position of the porphyrin monomer, the porphyrin polymer film being a porous porphyrin polymer film with mean pore diameters within the range of from 2 nm to 100 nm, and exhibiting a density not greater than 2 g/cm.sup.3. The invention also relates to a process for obtaining the multiply fused porphyrin polymer film coated on a substrate.

This invention is directed to separation, optimization and purification of nano-materials using self-assembled perylene diimide membranes, wherein said perylene diimide membrane is recyclable.