Creation of Well‐Defined “Mid‐Sized” Micropores in Carbon Molecular Sieve Membranes

• Published in: Angewandte Chemie 2019-09, Vol.131 (38), p.13393-13399
• Main Authors: Ma, Yao, Jue, Melinda L., Zhang, Fengyi, Mathias, Ronita, Jang, Hye Youn, Lively, Ryan P.
• Format: Article
• Language: English
• Subjects: Argon; Carbon; Chemistry; Fabrication; Form factors; Hollow fiber membranes; Kohlenstoff-Molekularsiebe; Low concentrations; Membrane permeability; Membranen; Membranes; Molecular sieves; Organic chemistry; Organic solvents; Polymere mit intrinsischer Mikroporosität; Polymers; Powder injection molding; Pyrolysis; Reverse osmosis; Selectivity; Solvents; Wasserstoff; Xylene; Xylol-Isomertrennung
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201903105

Carbon molecular sieve (CMS) membranes are 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 Å) microstructures that allow for 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 and ultimately results in the creation of a well‐defined bimodal pore network that exhibits an ultramicropore size of 5.1 Å. 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 PIM‐1 membranes pyrolyzed under a pure argon atmosphere. This approach is successfully extended to hollow fiber membranes operating in organic solvent reverse osmosis mode, highlighting the potential of this approach to be translated from the laboratory to the field. Die Pyrolyse von PIM‐1‐basierten Kohlenstoff‐Molekularsiebmembranen in einer H2‐Umgebung führt zu klar definierten „mittelgroßen” Mikroporen und einer drastischen Erhöhung der p‐Xylol‐durchlässigkeit mit einem geringen Verlust an p‐Xylol/o‐Xylol‐Selektivität.