Challenges and insights in CO2 adsorption using N-doped carbons under realistic conditions.

N-doped carbon was synthesized from an N-rich precursor, chitosan, and systematically compared with materials reported in the literature to evaluate its potential for CO2 capture in post-combustion scenarios and biogas upgrading under realistic conditions. The synthesized material, with 5.2 at.% nitrogen and a high surface area of 1000 m2 g-1, exhibited moderate CO2 uptake (2.6 mmol g-1) and an ideal CO2/N2 selectivity (SCO2/N2) of 20.4 under post-combustion conditions (15% vol. CO2, 1 bar, 298 K). For equimolar CO2/CH4 mixtures (50% vol. CO2), the material showed an ideal CO2/CH4 selectivity (SCO2/CH4) of 3.3 under the same conditions. When exposed to humidity, the material adsorbed CO2 efficiently at low relative humidity (RH) levels, but suffered a significant loss of capacity at 30% RH, attributed to water-induced site blocking. A comparison with other N-doped/enriched materials from the literature revealed difficulties in correlating CO2 adsorption and selectivity with specific material properties, such as surface area and nitrogen content. This underscores the complexity of defining universal design principles for CO2 capture.