Nanoporous Fluorinated\nCovalent Organic Framework\nfor Efficient C₂H₂/CO₂ Separation\nwith High C₂H₂ Uptake

Abstract

Effective C₂H₂/CO₂ separation\nis regarded as a crucial procedure in the C₂H₂ industry yet extremely challenging because of their similar physical\nand chemical properties. Covalent organic frameworks (COFs) have become\na promising platform for gas adsorption separation, but they still\nsuffer from unsatisfactory C₂H₂ adsorption capacity\nand selectivity. Herein, we report a nanoporous fluorine-functioned\nCOF (TpPa-F) for C₂H₂/CO₂ separation,\nwhich was synthesized by a mechanochemical approach with a F-containing\nprecursor (2-fluoro-1,4-benzenediamine). A superior C₂H₂ adsorption capacity of 117 cm³/g (4.78 mmol/g)\nand a C₂H₂/CO₂ selectivity of 3.3\nat 298 K and 1 bar were achieved, which surpass most of the reported\nCOF adsorbents in the literature. Notably, TpPa-F exhibited an extraordinary\nthermal stability of up to around 673 K and showed chemical robustness\nin organic or acidic/basic solutions. Theoretical calculations reveal\nthe hydrogen bond interaction of CC–H···F,\nwhich contributes to the high C₂H₂ uptake and\nseparation selectivity. This work provides a promising strategy of\nfluorine functionalization for enhancing the ability to recognize\nand separate small gas molecules in a large channel.