Hydrophobic Porous Polyketimines for the Capture of CO₂

A new type of porous polymers is presented. Polyketimines (PPKs) were synthesized by condensing 1,3,5-tris(4-aminophenyl)benzene with aromatic diketones using p-toluenesulfonic acid catalyst. They were characterized by infrared spectroscopy and solid-state ¹³ C{¹ H} nuclear magnetic resonance spectroscopy, and their porosities were probed through the adsorption of N₂ and CO₂ . The PPKs had low uptakes of N₂ (at -196 °C), which was attributed to diffusion limitations and/or a shrinking of the polymer. They had relatively high uptakes of CO₂ (at 0 °C; up to 1.26 mmol g^-1 at 0.15 bar and 2.99 mmol g^-1 at 1 bar), which was related to ultramicropores (6-9 Å). The PPKs had high estimated CO₂ -over-N₂ selectivities (30-40 at 0 °C). Studies on the vapor adsorption of water and ethanol showed the PPKs to be moderately hydrophobic and had a high uptake of ethanol at low partial pressures.