Fluorinated 2D Covalent Organic Frameworks with hcb Topology for Selective C2H4/C3H6 Separation

Abstract

Efficient separation of C₂H₄/C₃H₆ is essential for downstream polymer production, yet remains industrially challenging. Porous materials offer an energy-efficient alternative to cryogenic distillation, with fluorinated frameworks showing promise due to their tunable polarity and strong host–guest interactions. Herein, two isoreticular 2D covalent organic frameworks (COFs), TpDf-COF and TpTf-COF, with hcb topology were synthesized via [3+3] imine condensation. TpTf-COF, bearing a higher fluorine content, exhibits an IAST selectivity of 9.14 for C₂H₄/C₃H₆ at 298 K and 1 bar, outperforming TpDf-COF (6.57). GCMC simulations reveal that enhanced selectivity originates from increased pore polarity and strengthened C–H···F interactions with C₃H₆, highlighting the role of fluorination in modulating COF-based gas separation performance.