Imine-Linked Porous Polymer Frameworks with High Small Gas (H2, CO2, CH4, C2H2) Uptake and CO2/N2 Selectivity

A series of novel porous polymer frameworks (PPFs) with [3 + 4] structure motif have been synthesized from readily accessible building blocks via imine condensation, and the dependence of gas adsorption properties on the building block dimensions and functionalities was studied. The resulting imine-linked frameworks exhibit high surface area: the Brunauer-Emmett-Teller (BET) specific surface area up to 1740 m² g^-1, and a Langmuir surface area up to 2157 m² g^-1. More importantly, the porous frameworks exhibit outstanding H₂ (up to 2.75 wt %, 77 K, 1 bar), CO₂ (up to 26.7 wt %, 273 K, 1 bar), CH₄ (up to 2.43 wt %, 273 K, 1 bar), and C₂H₂ (up to 17.9 wt %, 273 K, 1 bar) uptake, which are among the highest reported for organic porous materials. PPFs exhibit good ideal selectivities for CO₂/N₂ (14.5/1-20.4/1), and CO₂/CH₄ adsorption (8.6/1-11.0/1), and high thermal stabilities (up to 500 C), thus showing a great potential in gas storage and separation applications.