Tailoring sub-3.3 Å ultramicropores in advanced carbon molecular sieve membranes for blue hydrogen production.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35263122.
- Also identified by DOI 10.1126/sciadv.abl8160 and PMC identifier 8906570.
- Licence recorded as CC BY-NC.
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Abstract
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° to 1200°C) to achieve sub-3.3 Å ultramicroporous channels for H<sub>2</sub>/CO<sub>2</sub> 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<sub>2</sub>/CO<sub>2</sub> separation properties. Specifically, polybenzimidazole (PBI) is cross-linked with pyrophosphoric acid (PPA) via H bonding and proton transfer before carbonization at ≤600°C. The synergistic PPA doping and subsequent carbonization of PBI increase H<sub>2</sub> permeability from 27 to 140 Barrer and H<sub>2</sub>/CO<sub>2</sub> selectivity from 15 to 58 at 150°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.