NOVELTY - Forming a carbon membrane using precursor pre-treatment comprises providing a polymer precursor, pre-treating a portion of the polymer precursor and subjecting the pre-treated polymer precursor to pyrolysis, where the step of pre-treating the portion of polymer precursor provides 300% increase in a gas permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment.    USE - The process is useful for forming a carbon membrane using precursor pre-treatment (claimed), where the carbon membrane includes an asymmetric carbon molecular sieve hollow membrane and is useful for separating first and second gases from a feed mixture of the first and second gases.    ADVANTAGE - The process enables efficient formation of the carbon membrane with improved thermal and/or mechanical properties, permeance and performance, and enhanced gas separation capability.    DETAILED DESCRIPTION - Forming a carbon membrane using precursor pre-treatment comprises: either providing a polymer precursor, pre-treating a portion of the polymer precursor and subjecting the pre-treated polymer precursor to pyrolysis, where the step of pre-treating the portion of polymer precursor provides 300% increase in a gas permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment; or providing a polymer precursor comprising a soluble thermoplastic polyimide, chemically modifying the polymer precursor with a modifying agent and heating the chemically modified precursor in a chamber to a temperature at which pyrolysis byproducts are evolved. INDEPENDENT CLAIMS are included for:    (1) modifying the polymer precursor for use as the carbon membrane, comprising providing the polymer precursor in a vessel, providing a modifying agent in the vessel, contacting a portion of the modifying agent with the polymer precursor in the vessel to provide for the modification of the portion of the polymer precursor, and subjecting the modified polymer precursor to pyrolysis for forming the carbon membrane; and    (2) the carbon membrane formed by the above process.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a scanning electron microscope image of a carbon molecular sieve membrane skin with morphology collapse from a precursor.