Effect of Nitrogen Doping on the CO₂ Adsorption Behavior in Nanoporous Carbon Structures: A Molecular Simulation Study

Nitrogen (N) doping is considered an effective design strategy to improve CO2 adsorption in carbon materials. However, experimental quantification of such an effect is riddled with difficulties, due to the practical complexity involved in experiments to control more than one parameter, especially at the nanoscale level. Here, we use molecular simulations to clarify the role of N doping on the CO2 uptake and the CO2/N2 selectivity in representative carbon pore architectures (slit and disordered carbon structures) at 298 K. Our results indicate that N doping shows a marginal improvement on the CO2 uptake, although it can improve the CO2/N2 selectivity. CO2 uptake and CO2/N2 selectivity are predominantly controlled by the pore architecture as well as ultra-micropores; the tendency of linear CO2 molecules to lie flat on the carbon surface favors the CO2 uptake in slit pore architectures rather than disordered carbon pore structures. We also demonstrated through molecular simulations that the N doping effect may be difficult to exemplify experimentally if the material has a disordered pore architecture and complex surface chemistry (such as the presence of other functional groups).