Highly Selective and Stable Carbon Dioxide Uptake in Polyindole-Derived Microporous Carbon Materials

Abstract

Adsorption with solid sorbents is considered to be one of the most promising methods for the capture of carbon dioxide (CO2) from power plant flue gases. In this study, microporous carbon materials used for CO 2 capture were synthesized by the chemical activation of polyindole nanofibers (PIF) at temperatures from 500 to 800 C using KOH, which resulted in nitrogen (N)-doped carbon materials. The N-doped carbon materials were found to be microporous with an optimal adsorption pore size for CO2 of 0.6 nm and a maximum (Brunauer-Emmett-Teller) BET surface area of 1185 m2 g-1. The PIF activated at 600 C (PIF6) has a surface area of 527 m2 g-1 and a maximum CO2 storage capacity of 3.2 mmol g-1 at 25 C and 1 bar. This high CO2 uptake is attributed to its highly microporous character and optimum N content. Additionally, PIF6 material displays a high CO2 uptake at low pressure (1.81 mmol g-1 at 0.2 bar and 25 C), which is the best low pressure CO2 uptake reported for carbon-based materials. The adsorption capacity of this material remained remarkably stable even after 10 cycles. The isosteric heat of adsorption was calculated to be in the range of 42.7-24.1 kJ mol-1. Besides the excellent CO2 uptake and stability, PIF6 also exhibits high selectivity values for CO2 over N2, CH4, and H2 of 58.9, 12.3, and 101.1 at 25 C, respectively, and these values are significantly higher than reported values.