Hyperaging Tuning of a Carbon Molecular‐Sieve Hollow Fiber Membrane with Extraordinary Gas‐Separation Performance and Stability

This study reports 6FDA:BPDA‐DAM polyimide‐derived hollow fiber carbon molecular‐sieve (CMS) membranes for hydrogen and ethylene separation. Since H2/C2H4 selectivity is the lowest among H2/(C1‐C3) hydrocarbons, an optimized CMS fiber for this gas pair is useful for removing hydrogen from all‐cracked gas mixtures. A process we term hyperaging provides highly selective CMS fiber membranes by tuning CMS ultramicropores to favor H2 over larger molecules to give a H2/C2H4 selectivity of over 250. Hyperaging conditions and a hyperaging mechanism are discussed in terms of an expedited physical aging process, which is largely controlled by the hyperaging temperature. For the specific CMS material considered here, a hyperaging temperature beyond 90 °C but less than 250 °C works best. Hyperaging also stabilizes CMS materials against physical aging and stabilizes the performance of H2 separation over extended periods. This work opens a door in the development of CMS materials for the separation of small molecules from large molecules. Better with age: So‐called hyperaging of carbon molecular‐sieve hollow fiber membranes at moderate elevated temperatures leads to a high separation performance for separating hydrogen and hydrocarbons. The system is stable over a long time and therefore very attractive for practical applications. This work provides an opportunity for tuning CMS fiber for the separation of small molecules from large molecules.