Fluorinated porous organic frameworks for improved CO₂ and CH₄ capture

Abstract

A porous 3D selectively fluorinated framework (F-PAF1), robust yet flexible and with a surface area of 2050 m² g^-1, was synthesised by condensation of an ad hoc prepared fluorinated tetraphenylmethane (TPM) monomer to ensure homogenously distributed C-F dipoles in the swellable architecture. Tetradentate TPM was also the comonomer for the reaction with fluorinated difunctional monomers to obtain frameworks (FMFs) with a controlled amount of regularly spaced reorientable C-F dipoles. The isosteric heat of adsorption of CO₂ was increased by 53% by even moderate C-F dipole insertion, with respect to the non-fluorinated frameworks. CO₂/N₂ selectivity was also increased up to a value of 50 for the difluoro-containing comonomer. Moreover, methane shows optimal interaction energies of 24 kJ mol^-1.