Enhanced Gas Separation Properties of Tröger’s Base Polymer Membranes Derived from Pure Triptycene Diamine Regioisomers

Most high-performance Tröger’s base (TB) polymers for gas separation membranes are from mixed diamine isomers, and the configuration differences in the polymer chain packing that arise from these isomers are still unknown. Herein three triptycene-containing Tröger’s-base-based polymers, CTTB (from pure Trip-2,6-diamine), MTTB (from pure Trip-2,7-diamine), and ITTB (from 50/50 Trip-2,6-diamine/Trip-2,7-diamine mixed regioisomers), were successfully synthesized and fully characterized. All polymers exhibited high thermal stability and rigidity, a large Brunauer–Emmett–Teller surface area, and distinct microporosity (pores <20 Å). ITTB showed the largest pores (ITTB (6.25 Å) > MTTB (6.15 Å) > CTTB (5.68 Å)) and pore-size distributions (ITTB (6.14–8.0 Å) > CTTB (5.48–7.0 Å) > MTTB (6.09–6.90 Å)). MTTB and CTTB showed outstanding H₂/CH₄, H₂/N₂, and O₂/N₂ separation performance that successfully surpassed the 2015 trade-off curves, better than those of the most recently reported state-of-the-art gas separation membranes and ITTB, due to their more uniform polymer main chain arrangement. This result shed light on the future high-performance gas separation polymer designs.