Synthesis of Diaminobipyridine-Triptycene Porous Copolymers for Gas Treatment

Designing porous polymers that balance structural stability, tunable porosity, and high selectivity is vital for efficient gas capture and separation. In this study, we synthesized two triptycene–bipyridine porous polymers, TPBP-1 and TPBP-2, using FeCl₃-catalyzed Friedel–Crafts crosslinking of triptycene with 5,5′-diamino-2,2′-bipyridine. Different monomer ratios were employed to control nitrogen-site density and free volume, resulting in amorphous, hyper-crosslinked polymers with high thermal stability above 300°C. TPBP-2, which contains more triptycene, exhibits a higher surface area (714 m²/g), larger pore volume, and increased CO₂ uptake capacity (2.42 mmol/g at 273 K and 1 bar). Conversely, TPBP-1, rich in diaminobipyridine, shows stronger CO₂ binding affinity (Q_st ≈ 26.6 kJ/mol) and enhanced selectivity for CO₂ over N₂ and CH₄ (CO₂/N₂ = 209; CO₂/CH₄ = 68). These variations demonstrate the tunable balance between adsorption capacity and selectivity, modulated by monomer ratio. The combination of triptycene's rigid, stable framework and diaminobipyridine's Lewis-basic nitrogen sites yields durable, high-performance adsorbents suitable for applications such as post-combustion carbon capture, natural gas upgrading, and hydrogen storage.