TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The second species is water. The first species is oxygen, and the second species is nitrogen.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Membrane: (s1) Are other than porphyrinic macrocycles; or planar porphyrinic macrocycles and the linkers connect pyrrole residues of adjacent macrocycles so that the linkers restrain the adjacent macrocycles such that their porphyrinic planes are in a non-co-planar orientation. (s1) Is connected by rigid linkers predominantly to a maximum of two other first species. The selective layer has a thickness of less than or equal to 1 (preferably 0.5, especially 0.05) microns. The supporting layer has a mean pore size of 10 - 20 (preferably 15) nm. (c1) Has an oxygen permeability of 5 m3/m2 h bar at 25degreesC not needed; and has an intrinsic oxygen/nitrogen selectivity of 5 at 25degreesC.Preferred Method: The solvent contains an organic additive (preferably 1 - 15%) possessing a boiling point below 120degreesC. The microporous material is at least partly cross-linked by treatment with a cross-linking agent before, during or after contacting the supporting layer with the solution of the microporous material. The supporting layer is treated with a first treatment solution comprising a gas permeable polymer before the supporting layer is contacted with the solution of the microporous material. The composite membrane once formed is treated with a second treatment solution comprising a gas permeable polymer. The mixture that is applied to the feed side of (c1) is in a gas, vapour or liquid phase.Preferred Components: The additive is selected from alcohol, ether, aromatic/aliphatic hydrocarbons, ketone, ester or their halogenated derivatives. The first and second species (preferably first) is an organic compound (preferably alcohol, phenol or a halogenated hydrocarbon compound); or the first and second species are organic compounds (preferably metal containing) and the first species is an isomer of the second species. The material comprises repeating spirocyclic heterocyclic unit of formula (A,B,C) that is optionally unsubstituted. The microporous material is a phthalocyanine network (preferably of formulae (II) or (IIa)).M = a metal ion or 2H+ (for a metal free macrocycle); andL1 = a linker group.Provided that when X is N and X1 is NH, then R1 is H only.    TECHNOLOGY FOCUS - POLYMERS - The supporting layer comprises an organic polymeric material selected from polyimide, polyamideimide, polyethersulfone, polyacrylate, polyphenylenesulfide or polyacrylonitrile. The gas permeable polymer is polydimethylsiloxane.