N-rich porous carbons with tunable affinity for CO2 adsorption achieve size-sieving CO2/N2 selectivity in turbostratic interlayers

While nitrogen- (N-) rich porous carbons hold promise to enable efficient carbon capture from post-combustion flue gas via temperature swing adsorption, a widespread tradeoff of surface chemistry with textural properties has resulted in a lack of detailed understanding in the relationships between a carbon adsorbent's material properties and its propensity for selective CO2 adsorption. This study details a comprehensive screening of the CO2 and N-2 adsorption performance for a set of turbostratic porous carbons with a wide range of microporosity (0-0.7 cm(3) g(-1)) and N-content (0-22 at%). By employing a temperature-dependent dual site Langmuir isotherm model, the energetics and capacities of CO2 adsorption were related to the carbons' textural and surface chemical properties. The isosteric heats of adsorption were dependent on the N content, with the most N-rich carbons exhibiting zero-loading isosteric heats upwards of 45 kJ mol(-1) compared to around only 20 kJ mol(-1) for unfunctionalized carbons. On the other hand, the N-2 adsorption was a strong function primarily of the surface area and microporosity. As a result, the selectivity and predicted carbon capture performance for a simplified temperature swing adsorption process model were shown to be highly tunable by enhancing the N content (and limiting the N-2-accessible porosity) of the carbon adsorbents. This work provides useful structure-function relationships and helps to answer the longstanding question of the validity of N-incorporation for tuning the CO2 adsorption performance of N-rich porous carbon adsorbents.