Construction and adsorption properties of porous aromatic frameworks via AlCl3-triggered coupling polymerization

Abstract

Currently, synthesis of most porous organic frameworks (POFs) requires noble metals as the main catalyst. Herein we report a low-cost and straightforward synthetic strategy to develop porous aromatic frameworks (PAFs). With AlCl₃ as the catalyst, the Scholl coupling reaction could occur between the phenyl rings of aromatic compounds. Using 3-dimensional monomers, such as triphenylamine, tetraphenylmethane, tetraphenylsilane, and tetraphenylgermane, we successfully obtained a series of PAFs with moderate Brunauer–Emmett–Teller (BET) surface areas ranging from 515 m² g⁻¹ to 1119 m² g⁻¹. Among the obtained PAF materials, PAF-41 exhibited the best CH₄ and CO₂ sorption capacity with CH₄ (1.04 mmol g⁻¹) and CO₂ (3.52 mmol g⁻¹) at 273 K. In addition, PAF-43 demonstrated its comparably high isosteric heat of adsorption at 34.8 kJ mol⁻¹ for CO₂ and 29.7 kJ mol⁻¹ for CH₄. It is also worth mentioning that the developed approach also overcomes typical flaws of some classic PAFs, such as high cost and complexity of precursor preparation.