Thermally Stable and High-Surface-Area Triptycene and Phenanthroline-Based Microporous Polymer for Selective CO₂ Capture over CH₄ and N₂

The increasing amount of CO₂ in the atmosphere is recognized as a major cause of global warming and its harmful consequences. Industrially, CO₂ is captured by chemisorption using amine-based solvents. However, there are major drawbacks to the wet-scrubbing process, including corrosion and high regeneration energy. The physical adsorption of CO₂ by using porous solid adsorbents is a viable and efficient alternative. Therefore, designing effective porous polymers with microporosity and polar functional groups using a simple approach is important for efficient carbon dioxide capture. This work describes the design, characterization, and CO₂ capture studies of a 3D-triptycene and phenanthroline-based microporous polymer (TPPM). The polymeric framework of TPPM is incorporated with 3D triptycene and phenanthroline as robust motifs to yield inflexible, twisted polymeric frameworks with an abundance of micropores and ultramicropores. This confers desirable features such as higher surface area, abundance microporosity, and physiochemical and thermal stability. TPPM demonstrated excellent thermal stability (T_d > 380 °C) with a larger BET-specific surface area of 1120 m² g^-1 and considerable microporosity, which makes it a promising adsorbent for CO₂ capture applications. The Morphological characterization of the polymer sample shows the formation of microspheres with diameters around 0.5-1 μm. TPPM has a strong affinity for CO₂ with Q_st of 23 kJ mol^-1 demonstrating promising CO₂ capture capacity of 2.76 mmol g^-1 at 273 K and 1.85 mmol g^-1 at 298 K where the micropore volume (V_mic = 0.445 cm³ g^-1) plays a potential role. The CO₂ capture capacity of TPPM outperforms several other literature-reported porous polymers. TPPM also demonstrated promising CO₂ selectivity over CH₄ and N₂, suggesting good promise for CO₂ adsorption and separation.