An amine functionalized carbazolic porous organic framework for selective adsorption of CO2 and C2H2 over CH4

Abstract

Abstract A new microporous organic polymer (PCB NH2) has been synthesized based on amine functionalized carbazole derivative by oxidative coupling polymerization with anhydrous FeCl3. Polymer PCB-NH2 exhibits microporous nature with a BET surface area of 542.4\u202fm2\u202fg−1, and shows moderately high CO2 and C2H2 adsorption capacities, 51.6\u202fcm3\u202fg−1 (10.3\u202fwt%), 58.4\u202fcm3\u202fg−1 (7.5\u202fwt%) at 278\u202fK, 1\u202fatm, respectively. Remarkably, at 278\u202fK, the predicted IAST selectivities of PCB-NH2 are 16.7–5.8 for a CO2/CH4 (5:95 v/v) gas mixture and 34.3–21.0 for a C2H2/CH4 (50:50 v/v) gas mixture at pressures varying from 0 to 1\u202fatm, respectively. More interesting, PCB-NH2 displays higher CO2/CH4 selectivity than its matrix polymer PCB. The isosteric heats of CO2 adsorption (Qst) for PCB-NH2 and PCB further indicate that the amine group may facilitate the interaction between the polarizable CO2 molecules and the polymer by local dipole−quadrupole interactions, subsequently favors selective gas separation for these gas molecules. The high selectivity of CO2/CH4 and C2H2/CH4 makes PCB-NH2 possible candidate for future natural gas upgrading and acetylene purification.