A fluorine-containing hydrophobic covalent triazine framework with excellent selective CO2 capture performance

Abstract

In this article, a set of fluorine functionalized covalent triazine-based frameworks have been designed and synthesized with 2,2′,3,3′,5,5′,6,6′-octafluoro-4,4′-biphenyldicarbonitrile as the monomer under typical ionothermal conditions. A prominent defluorination process during synthesis etches the networks to release CF_n, resulting in a significant loss of fluorine and carbon. Notably, the synergistic effects of polar C–F bonds and rich CO₂-philic N sites bestow upon the framework an excellent H₂ uptake (1.77 wt%, 77 K and 1 bar) as well as a significantly high CO₂ adsorption capacity (5.98 mmol g⁻¹, at 273 K and 1 bar), surpassing all related CTF materials measured under identical conditions that have been reported in the literature to date. Additionally, the material also exhibits a high CO₂/N₂ selectivity of 31 as predicted by the Henry model. The hydrophobicity of the CTF materials has been significantly enhanced owing to the incorporation of hydrophobic fluorine groups, which was further confirmed by ambient water vapor sorption.