Enhancing Gas Sorption and Separation Performance via Bisbenzimidazole Functionalization of Highly Porous Covalent Triazine Frameworks.

In this paper, a series of bisbenzimidazole-functionalized highly porous covalent triazine frameworks (CTF-BIBs) has been constructed from a new organic building block, 1,4-bis(5-cyano-1 H-benzimidazole-2-yl)benzene, via ionothermal polymerization. The physical porosity and gas adsorption properties of these CTF-BIBs were characterized, and the resulting CTF-BIBs exhibit significantly high Brunauer-Emmett-Teller surface areas (1636-2088 m2 g-1) and notable CO2 uptakes (86.4-97.6 cm3 g-1 at 273 K and 1 bar; 48.5-56.8 cm3 g-1 at 298 K and 1 bar). More importantly, these CTF-BIBs exhibit excellent selective separation abilities for CO2/N2, CO2/CH4, C2H6/CH4, and C3H8/CH4, particularly for equimolar mixtures C3H8/CH4 (386.6 for CTF-BIB-1 under 1 bar and 298 K). Furthermore, transient breakthrough simulations were carried out for equimolar CO2/C3H8/C2H6/CH4 mixtures, and CTF-BIBs display good separation performance in industrial fixed bed adsorbers. These results clearly demonstrate that the synthesized CTF-BIBs may serve as potential materials for CO2 capture and adsorptive separation for small hydrocarbons.