Carbon molecular sieve (CMS) membranes are promising candidates for the separation of organic molecules due to their stability, ability to be scaled to practical form factors, and the avoidance of expensive supports or complex multi-step fabrication processes. A critical challenge is the creation of “mid range” (e.g., 5-9 Å) microstructures that allow for both facile permeation of organic solvents and selection between similarly-sized guest molecules. Here, we create these microstructures via the pyrolysis of a microporous polymer (PIM-1) under low concentrations of H2 gas. The introduction of hydrogen inhibits aromatization of the decomposing polymer network and ultimately results in the creation of a well-defined bimodal pore network with the smallest micropores existing at 5.1 Å. The “H2-assisted” CMS membranes show a dramatic increase (~15 times) in p-xylene ideal permeability, while still maintaining commercially attractive p-xylene/o-xylene selectivities when compared to CMS membrane pyrolyzed under a pure argon atmosphere. This technique has the potential to be a platform technique for the creation of CMS microstructures capable of separating a wide variety of organic solvent molecules.

Creation of well-defined "mid-sized" micropores in carbon molecular sieve membranes for organic solvent separations

2019 Fall National Meeting

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