Scalable preparation of nitrogen-enriched carbon microspheres for efficient CO2 capture

Abstract

Monodispersed nitrogen-enriched carbon microspheres with uniform and tunable particle size and high nitrogen content were prepared by a simple carbonization of melamine–resorcinol–formaldehyde (MRF) microspheres. The MRF polymer microspheres were obtained by a hydrothermal polymerization at a temperature ranging from 80 to 180 °C and with a wide reactant concentration and a wide precursor composition. The synthesis is simple, scalable and very flexible, allowing the easy tailoring of the microsphere size and the nitrogen content in the carbon framework. The pores are created by the release of volatile matter during carbonization, giving a large fraction of fine micropores with a BET specific surface area of 400–800 m² g⁻¹. Further CO₂ activation can increase the BET surface area into the range 1500 to 1900 m² g⁻¹. Depending on the precursor composition, the nitrogen-enriched carbon microspheres contain 0–22.5 wt% of nitrogen atoms which are predominantly constituted by pyridinic-N, quaternary-N and oxynitride. CO₂ capture performances were evaluated between 273 K and 348 K, and very high adsorption capacity of 4.50 mmol g⁻¹ at 273 K, 1 bar is achieved. The facile and environmentally friendly production, scalable preparation, fast CO₂ adsorption kinetics and good regeneration performance make the prepared carbon microspheres useful for practical applications.