Fabrication of ultramicroporous triphenylamine-based polyaminal networks for low-pressure carbon dioxide capture

Three triphenylamine-based polyaminal networks (TMPs) with monodispersed ultramicropore (about 0.54 nm) and abundant doped-nitrogen (up to 42.88 wt%) are successfully prepared through the direct polycondensation of triphenylamine-based aldehydes with melamine. The synergistic effects of uniform ultramicropore and rich CO₂-philic polar sites endow TMPs with exceptional CO₂ sorption capacity and selectivity over N₂ and CH₄. For example, the CO₂ uptakes of TMPs can reach 15.7 wt% (273 K) and 11.2 wt% (298 K) at 1 bar. Especially, at a low pressure of 0.15 bar, TMP-3 simultaneously exhibits excellent CO₂ sorption capacity of 4.16 wt% (∼1 mmol g^-1, 298 K), high adsorption selectivities of CO₂/N₂ (61.9, 298 K) and CO₂/CH₄ (7.8, 298 K) and good cycle reusability, which are superior to most of the microporous polymers. In addition, the porous properties of TMPs could be effectively tuned by varying the amount of substitution formyl. This facile preparation method and excellent CO₂ adsorption properties enable TMPs to possess promising application potential in CO₂ capture and separation from low-concentration gas mixtures.