posted on 2022-02-09, 19:36authored byXinyi Wang, Trevor J. Wilson, Christopher R. Maroon, Jeffrey A. Laub, Savannah E. Rheingold, Konstantinos D. Vogiatzis, Brian K. Long
Natural
gas production and utilization have grown tremendously
in recent decades, which highlights the need for improved, high-throughput
purification methods. In the field of polymeric membrane-based gas
separations, a detailed understanding of molecular structure–property
relationships are critical to overcoming the permeability–selectivity
trade-off. Prior work has highlighted that alkoxysilyl-substituted
vinyl-addition polynorbornenes (VAPNBs) are promising candidates for
natural gas purification, having exceptional H2S/CH4 and modest CO2/CH4 permselectivity.
To improve their CO2/CH4 separation performance,
we herein describe a series of fluoroalkoxysilyl-substituted VAPNBs.
We demonstrate that the incorporation of fluoroalkoxysilyl substituents
yields a series of polymeric materials whose CO2/CH4 permselectivity increases as a function of fluorine incorporation.
Interestingly, these enhanced selectivity characteristics are realized
with minimal decreases to overall CO2 permeability. While
it was initially hypothesized that introduction of fluorinated units
would decrease CH4 solubility, detailed sorption analysis
revealed that the observed increases in CO2/CH4 permselectivity were due almost exclusively to enhanced CO2 sorption in fluorine-containing VAPNBs. Computational studies provided
insights into the electronic interaction energies between gas molecules
and polymer repeat units across the nonfluorinated and fluorinated
series, respectively.