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 (S_CO2/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 (S_CO2/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.