Nanoporous Fluorinated Covalent Organic Framework for Efficient C2H2/CO2 Separation with High C2H2 Uptake

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