Design and synthesis of carbazole-based conjugated microporous polymers for CO2 capture

Conjugated microporous polymers (CMPs) with electron-rich heteroatoms in the skeleton have been receiving continuous attention due to their huge potential for carbon dioxide (CO2) capture with high selectivity. Herein, we designed and synthesized three CMPs (MFCM-CMP, FFCM-CMP, and FFC-CMP-1) for CO2 capture. The MFCM-CMP and FFCM-CMP were obtained by the reaction between the similar carbazole- and fluorine-based building blocks and cyanuric chloride, while FFC-CMP-1 was synthesized by self-polymerization of 9,9′-(9,9-difluoro-9H-fluorene-2,7-diyl)bis(9H-carbazole) (FFC) building blocks. The as-prepared CMPs had high specific surface areas (SABET = 688–1245 m2/g), and hierarchical porous skeletons with average pore sizes ranging from 2.7 to 3.2 nm. Furthermore, all CMPs exhibited excellent gas (CO2, N2, CH4) uptake capacity. Remarkably, FFCM-CMP performed the CO2, N2, and CH4 uptake for 74.5 cm3/g, 4.2 cm3/g, and 17.4 cm3/g at 273 K, 1.0 bar, and the CO2 capture selectivity could achieve 19.6 and 4.3 from CO2/N2 (15/80) and CO2/CH4 (50/50) mixture at 298 K, 1.0 bar, respectively. The gas breakthrough test carried out in CO2/N2/Ar (15/80/5) disclosed evidently that the synthesized CMPs with triazine groups exhibited outstanding CO2 capture selectivity. This work provides a new strategy for porous organic adsorbents for improving CO2 selectivity from the molecular level. © 2024