The effects of nitrogen functional groups and narrow micropore sizes on CO2 adsorption onto N-doped biomass-based porous carbon under different pressure

Abstract The biomass-derived N-doped porous carbons have been proved promising adsorbent material, due to their good CO2/N2 selectivity and excellent CO2 adsorption performance. However, many researchers simply studied the effect of nitrogen groups or narrow micropores (less than 0.7 nm) on CO2 uptake at 1 bar and ignored the role of different pressures. In this study, a promising porous carbon derived from eucalyptus bark with high CO2 adsorption capacity was prepared by urea-assisted hydrothermal and KOH activation. The obtained porous carbons were found to be mainly microporous and showed rich nitrogen content. Among the materials, at 1 bar, NPC700 exhibits high CO2 adsorption of 4.20 mmol/g and 6.98 mmol/g at 25 °C and 0 °C, respectively. Based on Grand canonical Monte Carlo (GCMC) simulation, the adsorption density and adsorption energy on graphite slit pore with different pore sizes (0.6–2.0 nm) and N-doped functional groups (pyridinic-N, pyrrole-N and graphitic-N) were calculated. And the results showed that the nitrogen functional groups played a crucial contribution on CO2 adsorption capacity at relative low pressure (0–0.16 bar). In the case of relative high pressure (0.16–1 bar), the narrow micropores volume determined the CO2 uptake capacity.