Flexible chain & rigid skeleton complementation polycarbazole microporous system for gas storage

Abstract

Abstract Five flexible chain & rigid skeleton complementation polycarbazole networks P-Fo, PBT-C1 (C2, C4, C6) were designed and synthesized for gas storage. Increasing the length of alkyl groups from naked to –CH3 to –n-C6H12, the morphology (SEM) and thermostability (TGA) got tremendous changes. PBT-C1 exhibited Brunauer-Emmett-Teller (BET) specific surface area of 685\u202fm2\u202fg−1, which is larger than network P-Fo without TTF substitutions. Nevertheless, further replacing the alkyl-substituted TTF motifs with longer alkyl chains (PBT-C2, C4, C6) would bring a dramatic drop of BET surface areas to less than 100\u202fm2\u202fg−1, similar trends have found for H2, CO2, and CH4 adsorption as side chains changed. It need to be mention that decorating the alkyl group, CH4 adsorption enthalpy can be significantly improved to 52.1\u202fkJ\u202fmol−1 (PBT-C4) at zero loading, indicating that alkyl segment can promote the adsorption potential between microporous and CH4 molecule, while have futile effect on H2 and CO2 molecule. These results demonstrated that rational flexible chain grafted into the rigid skeleton at one hand can block the microporous, but it will also have more beneficial on the BET surface areas, pore volume and gas adsorption ability, especially for methane.