TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The gas pair is oxygen/nitrogen, carbon dioxide/methane, carbon dioxide/nitrogen, hydrogen/nitrogen, helium/nitrogen, hydrogen/methane, helium/methane, helium/hydrogen, hydrogen/carbon dioxide, water/at least one other gas, and helium/carbon dioxide.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The polymer backbone structures of the polymeric matrix are not changed. In the method, T is less than Tg. The polymeric matrix is crosslinked prior to the degrading step, so as to hinder a relaxation process for the polymer and hinder free volume loss. The polymeric matrix is crosslinked during the degrading step. The method of preparing a polymeric material further comprises inducing phase inversion of the polymeric matrix to provide the polymeric material in a form of an asymmetric membrane. Preferred Components: The permeability of the polymeric material is at least 5 times the permeability of the polymeric matrix for the gas, and the selectivity of the polymeric material is at least 0.35 times the selectivity of the polymeric matrix for the gas pair. The polymer has: a glass transition temperature higher than 100 degrees C; and an average molecular weight of 10000-400000. The polymer is at least one member including polyamides, polyimides, poyletherimides, polyethersulfones, polysulfones, polybenzimidazoles, polybenzobenzimidazoles, poly(aryl ether ketones), poly(aryl ethers), aromatic polyarylates, aromatic polycarbonates, poly(benzoxazoles), poly(amide-imides), poly(oxadiazole-imides), poly(etherimides), poly(aryl sulfides), polybenzothiazoles, polypyrrolones, polyoxadiazoles, polytriazoles, polyesterimides, poly(phenyl quinoxaline) and poly(phenylenes), and/or their copolymers. The polymer is of formula (-X(L-LG)-) (I) and the porogen is of formula (-X-LG-) (II). The polymer is a polyimide and the porogen is not carboxylic acid or sulfonic acid. The porogen is: an additive miscible in the polymeric matrix; at least one member including aliphatic hydrocarbons, aliphatic carboxylic acids and esters, aliphatic ethers and thioethers, aliphatic carbonates, aromatic carboxylic acids and esters, aromatic carbonates, crown ethers, calixarenes, cyclic structures of aromatic linked groups with labile linking groups, cyclic structures of polyesters, blocked isocyanates, aliphatic and aromatic thiosulfates, bisulfide compounds, organo-onium compounds, Diels-Alder adducts, azo compounds, blowing agents, photo acid generators, sulfur, organic sulfonic acids and sulfates, organic sulfites, alpha -terpinene, d-limonene, rosin and/or abetic acid esters; or a small molecule, oligomer or a polymer. The porogen is: an aliphatic carboxylic acid or an azo compound; and 1-40 wt.% of the polymer. The polymer is a polyimide or polysulfone. The membrane exceeds Robeson's upper bound relationship for at least one gas separation pair. The membrane is asymmetric and comprises hollow fibers.X = polymer backbone;LG = labile group porogen that degrades upon exposure to the treatment to yield products that diffuse out of the polymeric matrix, preferably aliphatic hydrocarbon groups, ester groups, thioester groups, aliphatic ether groups, aliphatic carbonate groups, halogen groups, aliphatic and aromatic sulfonate, aliphatic and aromatic phosphonates, bisulfide groups, azo groups, blocked isocyanate groups, carboxylate, Diels-Alder adducts, organo-onium, quaternized ammonium, N-alkylated heteroaryl groups and/or thiosulfate groups; andL = direct bond between LG and the polymer backbone, 1-40C linking group or 0-40C non-carbon linking group, preferably alkyl, alkenyl, alkynyl, aryl, heteroaryl, O, N, S, F, Cl, Br or Si. EXAMPLE - Poly(4,4'-(hexafluoroisopropylidene)diphthalic anhydride)-(3,5-diaminobenzoic acid)-(2,4,6-trimethyl-1,3-phenylenediamine) (3.09 g) was dissolved in 2-pentanone (10.55 g) in 4 oz glass bottle. The bottle was placed on a roller mill and rolled overnight to obtain a homogenous solution. Then malonic acid (0.15 g) was added to the homogenous solution and rolled overnight on a roller mill to get polymer solution. Glass plate was cleaned by sonicating in soapy de-ionized water for at least 10 minutes, and rinsed with de-ionized water. After drying in air, the glass plate was rinsed and wiped with acetone and then heptane using clean room wipes and allowed to air dry. Polymer solution (2 g) was poured on the glass plate in a line and drawn down using a draw-down bar. The wet coating was placed in a nitrogen purge box. After overnight, the glass plate and coating was removed from nitrogen purge box and placed in de-ionized water. The coating was separated from the glass plate and was allowed to air dry to obtain film.