Low-Temperature and Single-Step Synthesis of N‑Doped Porous Carbons with a High CO2 Adsorption Performance by Sodium Amide Activation

In this study, N-enriched porous carbons were prepared by a facile synthesis method at low temperatures ranging from 400 to 500 °C. Sodium amide was used as both activator and nitridation reagent, and lotus stalk was used as the carbon precursor. The as-synthesized samples demonstrate the maximum CO2 uptake of 3.88 and 5.62 mmol/g at 25 and 0 °C, respectively, at atmospheric pressure. Moreover, these lotus stalk-derived adsorbents exhibit a rapid CO2 adsorption rate, high CO2/N2 selectivity, moderate CO2 isosteric heat of adsorption, stable cyclic ability, and excellent dynamic CO2 capture capacity. Systematic research shows that, besides the volume of narrow micropore and nitrogen content, the pore size distribution is also a non-negligible factor in determining CO2 adsorption capacity under ambient condition for these adsorbents. The good CO2 adsorption performance together with single-step and low-temperature preparation indicates that these sorbents are very promising for CO2 capture from flue gas.