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.