Pore Modulation by Etching Silicon-Rich Porous Aromatic Frameworks for CO₂ Capture

Excessive CO₂ emission has led to environmental damage. Efficient CO₂ capture is a key strategy for mitigation. Given the low CO₂ concentration in air, appropriate adsorbent affinity is required. However, high affinity hinders regeneration, while low affinity reduces capacity. Therefore, maintaining adsorption enthalpy within an ideal range for efficient and reversible adsorption has long been a challenge. In this study, a silicon-rich porous aromatic framework, namely, PAF-141, was synthesized via a Scholl coupling reaction using octaphenyl-functionalized polyhedral oligomeric silsesquioxane and biphenyl as monomers. A fluorinated derivative, PAF-141-F, was subsequently obtained through hydrofluoric acid etching of silicon sites. Both materials exhibited high specific surface areas and good thermal stability. Under conditions of 273 K and 1 bar, the CO₂ adsorption capacities for PAF-141 and PAF-141-F were measured to be 42.10 and 39.38 cm³/g, respectively. Notably, PAF-141-F demonstrated superior pore affinity toward CO₂ at 298 K, with Q_st of 44.33 kJ/mol, which fell within an ideal range. This indicated its strong adsorption capacity and reversible adsorption-desorption performance. Furthermore, IAST calculations revealed that both materials possessed high selectivity for CO₂/N₂ separation, demonstrating their potential for efficient CO₂ capture.