Carbon molecular sieve membranes, methods of manufacturing, and use thereof

A method of manufacturing a carbon molecular sieve (CMS) membrane, the method comprising:

• forming a copolymer into one or more hollow fibers comprising polyimide or one or more microcapillary films comprising polyvinylidene chloride (PVDC);
• pyrolyzing the one or more hollow fibers or the one or more microcapillary films at a second temperature of from 600° C. to 700° C. with inert gas or under vacuum;
• annealing the one or more hollow fibers or the one or more microcapillary films at a third temperature of from 900° C. to 1500° C. with inert gas or under vacuum;
• and
• oxidizing the one or more hollow fibers or the one or more microcapillary films at a fourth temperature of from 700° C. to 900° C. with carbon dioxide, wherein:
• the one or more microcapillary films are pretreated prior to pyrolyzing by heating at a first temperature of from 120° C. to 200° C. with air, the inert gas, under vacuum, or combinations thereof,
• the annealing step occurs after observing greater than or equal to 70 percent weight loss of the one or more hollow fibers or the one or more microcapillary films in the pyrolyzing step, and
• the oxidation step is stopped at less than 20 wt. % loss of the one or more hollow fibers or the one or more microcapillary films in the oxidation step.