(278c) Creation of Well-Defined “Mid-Sized” Micropores in Carbon Molecular Sieve Membranes

Carbon molecular sieve (CMS) membranes are promising candidates for the separation of organic molecules due to their stability, ability to be scaled at 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 Ã…) 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 hydrogen gas. The introduction of H₂ 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 Ã…. The H₂ assisted CMS dense membranes show a dramatic increase in p-xylene ideal permeability (~15 times), with little loss in p-xylene/o-xylene selectivity (18.8 vs. 25.0) when compared to dense PIM-1 membranes pyrolyzed under a pure argon atmosphere. This approach is extended to hollow fiber membranes, which exhibit p-xylene permeances up to 5.2×10^-10with permselectivities of 8.9 for equimolar p-xylene/o-xylene mixtures, highlighting the potential of this approach to be translated from the laboratory to the field.