Journal
SCIENCE ADVANCES
Volume 8, Issue 10, Pages -Publisher
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/sciadv.abl8160
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Funding
- U.S. Department of Energy (DOE) [DE-FE0031636]
- U.S. National Science Foundation (NSF) [1804996]
- U.S. Department of Commerce, National Institute of Standards and Technology (NIST) [70NANB18H226]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1804996] Funding Source: National Science Foundation
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By doping polymers with thermolabile cross-linkers before low-temperature carbonization, the processability of the polymers can be retained and superior hydrogen/carbon dioxide separation properties can be achieved.
Carbon molecular sieve (CMS) membranes prepared by carbonization of polymers containing strongly size-sieving ultramicropores are attractive for high-temperature gas separations. However, polymers need to be carbonized at extremely high temperatures (900 degrees to 1200 degrees C) to achieve sub-3.3 angstrom ultramicroporous channels for H-2/CO2 separation, which makes them brittle and impractical for industrial applications. Here, we demonstrate that polymers can be first doped with thermolabile cross-linkers before low-temperature carbonization to retain the polymer processability and achieve superior H-2/CO2 separation properties. Specifically, polybenzimidazole (PBI) is crosslinked with pyrophosphoric acid (PPA) via H bonding and proton transfer before carbonization at <= 600 degrees C. The synergistic PPA doping and subsequent carbonization of PBI increase H-2 permeability from 27 to 140 Barrer and H-2/CO2 selectivity from 15 to 58 at 150 degrees C, superior to state-of-the-art polymeric materials and surpassing Robeson's upper bound. This study provides a facile and effective way to tailor subnanopore size and porosity in CMS membranes with desirable molecular sieving ability.
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