Synthesis of monodisperse highly nitrogen-rich porous carbon microspheres for CO2 adsorption.

The nitrogen-rich carbon microspheres were prepared by the one-pot hydrothermal synthesis in the presence of resorcinol formaldehyde as the carbon precursor and tetraethylenepentamine (TEPA) as nitrogen precursor as well as the base catalyst, followed by carbonization and activation. Their nitrogen content and microstructure of the nitrogen-rich carbon microspheres could be adjusted by varying the addition of TEPA. The significant enhancement of the microstructure and the nitrogen doping leads to high CO₂ adsorption in the activated carbon microspheres. The high nitrogen content of activated sample AMPS-4 was 5.61%, and the large specific surface area and micropore volume were 786.5 m²/g and 0.28 cm³/g, respectively. The activated sample AMCS-4 had the highest CO₂ adsorption reaching 5.52 mmol/g and 2.97 mmol/g at 0 and 25 °C, respectively. Compared with EDA-prepared carbon microspheres AMCS-4E, TEPA-prepared carbon microspheres AMCS-4 have stabler chemical adsorption to CO₂ due to their higher nitrogen content, which is in corresponds to the higher adsorption heat. The introduction of polyvinylpyrrolidone (PVP) into the system as a stabilizer not only improved the monodispersity of carbon microspheres but also improved the adsorption performance of CO₂ by increasing the micropore volume and decreasing the micropore size of the microspheres. The CO₂ adsorption of the PVP-assisted prepared sample AMCS-2-P1 reached 4.48 mmol/g and 2.95 mmol/g at 0 °C and 25 °C respectively, which is 0.72 mmol/g and 0.25 mmol/g higher than that of AMCS-2. The carbon microspheres have high CO₂ dynamic adsorption capacity, excellent selective adsorption, and good cyclic stability. Highlights: Monodisperse highly N-rich carbon microspheres were prepared by a one-step hydrothermal method. The microspheres have a good monodisperse, improved microstructure, and high N content. The microspheres have high CO₂ adsorption capacity, good selective adsorption, and cycling stability. [ABSTRACT FROM AUTHOR]