Freeze Casting of Microporous Composite Beads Based on a Polymer of Intrinsic Microporosity for Gas Storage Applications

Polymers of intrinsic microporosity (PIMs) show potential for gas storage and separation applications. However, they are often produced in fine-scale particulate form which can lead to handling and fouling issues, for example when inserted inside storage tanks. We provide the first demonstration of a manufacturing technique to form millimeter scale PIM-based beads by freeze casting PIM-1 droplets. The PIM-based beads are shown to exhibit similar Brunauer-Emmett-Teller (BET) surface areas compared to its original particulate form and low pressure hydrogen isotherms (to 0.1 MPa) are presented to examine gas storage behavior. We also demonstrate the production of composite PIM-1 beads containing up to 80 wt % of activated carbon filler, which leads to improved surface area for gas storage and separation, generally following the rule of mixtures. The composite beads can store 1.6 wt % hydrogen at 0.1 MPa and 77 K and are predicted to have a maximum storage capacity of 8.1 wt %, with potential to meet the Department of Energy (DoE) targets for light duty fuel cell vehicles.