Tailoring the pore chemistry in porous aromatic frameworks for selective separation of acetylene from ethylene

Abstract

The separation of acetylene from ethylene is a crucial process in the petrochemical industry, because even traces of acetylene impurities can poison the catalysts of ethylene polymerization. Herein, we synthesize a new family of 3D porous aromatic frameworks (PAFs), non-functionalized PAF-28, carbene-functionalized PAF-28 (cPAF-28) and imidazolium-functionalized PAF-28 (iPAF-28), via Sonogashira coupling reactions. These PAFs show high porosity and good thermal stability. Both cPAF-28 and iPAF-28 are proved to be good candidates for C₂H₂ adsorption, demonstrated by C₂H₂/C₂H₄ selectivity of 12.2 and 15.4, and C₂H₂ capacity of 48 cm³ g⁻¹ and 57 cm³ g⁻¹, which are significantly higher than those of non-functionalized PAF-28 (1.8, 37 cm³ g⁻¹). Furthermore, the cPAF-28 and iPAF-28 display good breakthrough performance and remarkable recyclability for the separation of the C₂H₂/C₂H₄ gas mixture. In addition, the C₂H₂/C₂H₄ adsorption sites are revealed by DFT calculations. This work sheds a new light on gas molecular recognition by tailoring the pore chemistry of PAFs.