N-doped porous carbons with exceptionally high CO2 selectivity for CO2 capture

Porous carbons have been considered to be promising sorbents for carbon capture and sequestration. For achieving high capture capacity and CO2/N2 selectivity, precise control of porous structures and surface polarity is necessary. Herein we report the preparation of N-doped porous carbon via pyrolysis of microporous polyindole with KOH as the activator under N2. Analysis results suggest that nitrogen amounts and textural properties of carbon materials could be adjusted by KOH content and pyrolysis temperature. Generally, higher Vultramicro/Vmicro ratio (up to 0.64) and higher N-doping amounts (up to 6.87 wt%) could be obtained at a relative low pyrolysis temperature and KOH content. Impressively, the porous carbons show extremely high Henry's CO2/N2 selectivity up to 136 at 298 K, among the highest of carbon based materials. Even measured using simulating flue gas (15% CO2/85% N2) at 308 K, the porous carbons also afford very high CO2/N2 selectivity of 63 with high CO2 adsorption capacity of 1.42 mmol/g. The high CO2/N2 selectivity and CO2 uptake capacity under flue gas are mainly related with high Vultramicro/Vmicro ratio and N content of porous carbons. Our results imply that porous carbons with optimized surface polarity and porous structure are promising solid adsorbents for CO2 capture.