Ionomers of Intrinsic Microporosity: In Silico Development
of Ionic-Functionalized Gas-Separation Membranes
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Abstract
This work presents the predictive
molecular simulations of a functionalized
polymer of intrinsic microporosity (PIM) with an ionic backbone (carboxylate)
and extra-framework counterions (Na<sup>+</sup>) for CO<sub>2</sub> gas storage and separation applications. The CO<sub>2</sub>-philic
carboxylate-functionalized polymers are predicted to contain similar
degrees of free volume to PIM-1, with Brunauer–Emmett–Teller
(BET) surface areas from 510 to 890 m<sup>2</sup>/g, depending on
concentration of ionic groups from 100% to 17%. As a result of ionic
groups enhancing the CO<sub>2</sub> enthalpy of adsorption (to 42–50
kJ/mol), the uptake of the proposed polymers at 293 K exceeded 1.7
mmol/g at 10 kPa and 3.3 mmol/g at 100 kPa for the polymers containing
100% and 50% ionic functional groups, respectively. In addition, CO<sub>2</sub>/CH<sub>4</sub> and CO<sub>2</sub>/N<sub>2</sub> mixed-gas
separation performance was evaluated under several industrially relevant
conditions, where the IonomIMs are shown to increase both the working
capacity and selection performance in certain pressure swing applications
(e.g., natural gas separations). These simulations reveal that intrinsically
microporous ionomers show great potential as the future of energy-efficient
gas-separation polymeric materials