A rational construction of microporous imide-bridged covalent–organic polytriazines for high-enthalpy small gas absorption

Abstract

A series of microporous imide functionalized 1,3,5-triazine frameworks (named TPIs@IC) were designed by an easy-construction technology other than the known imidization method for the construction of porous triazine-based polyimide networks (TPIs) with the same chemical compositions. In contrast to TPIs, TPIs@IC exhibit much higher Brunauer–Emmett–Teller (BET) surface areas (up to 1053 m² g⁻¹) and carbon dioxide uptake (up to 3.2 mmol g⁻¹/14.2 wt% at 273 K/1 bar). The presence of abundant ultramicropores at 5.4–6.8 Å, mainly ascribed to a high-level cyano cross-linking, allows the high heat absorption and high selective capture of CO₂. The Q_st (CO₂ esoteric enthalpies) from their CO₂ adsorption isotherms at 273 and 298 K are calculated to be in the range 46.1–49.3 kJ mol⁻¹ at low CO₂ loading, and the ideal CO₂/N₂ separation factors are up to 151, exceeding those of the most reported porous organic polymers to date. High storage capacities of TPIs@IC for other small gases like CH₄ (5.01 wt% at 298 K/22 bar) and H₂ (1.47 wt% at 77 K/1 bar) were also observed, making them promising adsorbents for gas adsorption and separation.