Synthesis and gas separation properties of OH-functionalized Tröger's base-based PIMs derived from 1,1′-binaphthalene-2,2′-OH

Two novel OH-functionalized intrinsically microporous polymers were successfully synthesized from a tert-butyldimethylsilyl (TBS) protected 1,1′-binaphthalene-diamine monomer (NH2-BINOL-TBS). Interestingly, the polymerization and the removal of the TBS to form OH group happened at the same time. Polymers with 30% (PIM-HNTB-30) and 60% (PIM-HNTB-60) OH concentration were obtained by controlling the reaction time of 3.5 and 12 h, and confirmed by nuclear magnetic resonance spectroscopy (NMR). PIM-HNTB-30 exhibited higher Brunauer-Emmett-Teller (BET) surface area (432 vs 153 m2 g-1) and thermal stabilities (420 vs 385 °C) than PIM-HNTB-60. Both membranes showed modest gas permeabilities and selectivities, and PIM-HNTB-60 exhibited a relatively higher performance. After long-term aging or thermally annealed above glass transition temperature (Tg), both polymers exhibited a decreased permeabilities combined with a selectivity increase, and the 350 °C treated PIM-HNTB-60 exhibited O2 permeability of 89 Barrer and O2/N2 selectivity of 4.47. In all, the OH functionalization provided a good way to enhance the gas separation performance.