Highly Nitrogen-Rich Microporous Polyaminals Using N,N-Dimethylformamide and Formamide as the Starting Monomers for CO₂ Adsorption and Separation

A series of highly nitrogen-rich microporous polymers are prepared from triazine-based tetraamines (p-BzDAT and m-BzDAT) and hexaamine (TMBDAT) with formamide (MF) and N,N-dimethylformamide (DMF). p-BzDAT and m-BzDAT are isomers with two triazinediamines para- and meta-substituted on a benzene ring, respectively, whereas TMBDAT has three triazinediamines 1,3,5-substituted on trimethylbenzene. The different geometry configurations and functionalities of the starting monomers result in tunable Brunauer–Emmett–Teller areas and pore sizes in the ranges of 842–1227 m² g–¹ and 0.53–3.82 nm, respectively. The synergistic effects of porosity parameters and CO₂-philic groups including triazine rings and various amines in the porous polymer networks on CO₂ adsorption and separations are systematically studied. Of interest is the observation that the sample derived from DMF and p-BzDAT displays simultaneously high CO₂ uptake of 20.3 wt % and a dynamic CO₂/N₂ separation factor of 127.6 at 1 bar/273 K, which overcomes the adsorption selectivity trade-off dilemma often encountered in the previous studies, showing promising applications in the CO₂ sequestration field.