| Summary: | Separation of CO<sub>2</sub>/CH<sub>4</sub>/N<sub>2</sub> is significantly important from the view of environmental protection and energy utilization. In this work, we reported nitrogen (N)-doped porous carbon spheres prepared from sustainable biomass glucose via hydrothermal carbonization, CO<sub>2</sub> activation, and urea treatment. The optimal carbon sample exhibited a high CO<sub>2</sub> and CH<sub>4</sub> capacity, as well as a low N<sub>2</sub> uptake, under ambient conditions. The excellent selectivities toward CO<sub>2</sub>/N<sub>2</sub>, CO<sub>2</sub>/CH<sub>4</sub>, and CH<sub>4</sub>/N<sub>2</sub> binary mixtures were predicted by ideal adsorbed solution theory (IAST) via correlating pure component adsorption isotherms with the Langmuir−Freundlich model. At 25 °C and 1 bar, the adsorption capacities for CO<sub>2</sub> and CH<sub>4</sub> were 3.03 and 1.3 mmol g<sup>−1</sup>, respectively, and the IAST predicated selectivities for CO<sub>2</sub>/N<sub>2</sub> (15/85), CO<sub>2</sub>/CH<sub>4</sub> (10/90), and CH<sub>4</sub>/N<sub>2</sub> (30/70) reached 16.48, 7.49, and 3.76, respectively. These results should be attributed to the synergistic effect between suitable microporous structure and desirable N content. This report introduces a simple pathway to obtain N-doped porous carbon spheres to meet the flue gas and energy gas adsorptive separation requirements.
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