Sustainable Biomass Glucose-Derived Porous Carbon Spheres with High Nitrogen Doping: As a Promising Adsorbent for CO₂/CH₄/N₂ Adsorptive Separation

Separation of CO₂/CH₄/N₂ 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, CO₂ activation, and urea treatment. The optimal carbon sample exhibited a high CO₂ and CH₄ capacity, as well as a low N₂ uptake, under ambient conditions. The excellent selectivities toward CO₂/N₂, CO₂/CH₄, and CH₄/N₂ 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 CO₂ and CH₄ were 3.03 and 1.3 mmol g^-1, respectively, and the IAST predicated selectivities for CO₂/N₂ (15/85), CO₂/CH₄ (10/90), and CH₄/N₂ (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.