A Carboxyl-Functionalized Pentiptycene-Based Nanoporous Organic Polymer for Selective Ammonia Capture from Dry N2/H2 Mixtures

Selective NH3 removal from N2/H2-rich streams requires porous adsorbents with reversible and preferential NH3-binding sites. Herein, we report a carboxyl-functionalized pentiptycene-based nanoporous organic polymer (PNOP-1) prepared by one-pot Friedel–Crafts polymerization of pentiptycene quinone and pyromellitic dianhydride. The rigid pentiptycene scaffold creates permanent microporosity, whereas dianhydride-derived carboxyl/carbonyl groups provide additional interaction sites for NH3 adsorption. PNOP-1 adsorbs 10.4 mmol·g–1 NH3 at 298 K and 100 kPa, accompanied by substantially lower N2 and H2 uptake. Dry-gas breakthrough experiments, isosteric heat of adsorption, and molecular simulations suggest that micropore confinement together with favorable NH3–oxygen interactions contributes to the observed selectivity.