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The design and synthesis of porous carbons with unique structures and diverse functionalities as CO2 adsorbents constitute a challenging and intriguing research topic. In this study, the synthesis of hollow micro-mesoporous nitrogen-doped carbon nanoparticles (NPCS) and its adsorption of CO2 were investigated. Highly porous nitrogen-doped carbon nanoparticles were successfully synthesized by using economically available resorcinol and formaldehyde as carbon precursors, with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (KH-792) as a soft template and silica sol as a hard template. The hollow nitrogen-doped carbon nanoparticles exhibit an evident microporous-mesoporous structure and have two different scales of mesopores with 9 nm and 12 nm, respectively. The effects of various synthetic parameters on the formation of hollow nitrogen-doped carbon nanoparticles were analyzed. The hollow nitrogen-doped carbon nanoparticles exhibited specific surface area of 1090 to 1716 m2/g and nitrogen content of 2.83 to 5.28%. At 273 K and 1 bar, the experimental results demonstrated the positive effects of the enriched pore structure and nitrogen doping on CO2 adsorption. The optimum adsorption capacity of activated NPCS (ANPCS) was 5.11 mmol/g with excellent CO2/N2 selectivity value of 20.44 at 273 K and 1 bar. The initial heat of adsorption value for ANPCS was 30.90 KJ/mol. Additionally, the hollow nitrogen-doped carbon nanoparticles retained 99.2% of the initial adsorbed amount after 5 cycles of adsorption. The excellent adsorption performance of the material can be ascribed not only to its extensive specific surface area and enriched nitrogen but also to its mesoporous and hollow structure, which facilitates rapid CO2 transport. Highlights: The combination of soft and hard templates was used to prepare hollow micro-mesoporous nitrogen-doped carbon nanoparticles. N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is used not only as structure-directing and pore-forming agent, but also nitrogen source. The carbon nanoparticles have excellent CO2 adsorption due to their large specific surface area, high nitrogen content and mesoporous hollow structures. The mesoporous and hollow structures leads to high CO2 transport rates in carbon nanoparticles. [ABSTRACT FROM AUTHOR]

Nitrogen-rich hollow carbon microspheres were successfully synthesized using resorcinol and formaldehyde as carbon sources, tetraethylenepentamine (TEPA) as a catalyst, and nitrogen source, with SiO2 microspheres as a hollow template. The hollow carbon microspheres were prepared by adding varying amounts of SiO2 hollow templates to a fixed amount of TEPA. The shell thickness increased as the amount of SiO2 template decreased and the shell thicknesses of AHMCS-2(1), AHMCS-2(3), and AHMCS-2(5) were 28.5 nm, 17.3 nm, and 12.7 nm, respectively. The activated hollow carbon microspheres (AHMCS-2(1), AHMCS-2(3) and AHMCS-2(5)) contained 4.66%, 5.05%, and 3.27% nitrogen, respectively. Due to the sufficient activation process, the specific surface area and microporous volume of hollow carbon microspheres are greatly increased compared to solid carbon microspheres, therefore, their CO2 adsorption performance is superior as well. As the shell layer thickens, the specific surface area and micropore volume of the activated hollow carbon microspheres increased, among which AHMCS-2(1) showed the largest specific surface area and micropore volume of 1146 m2/g and 0.45 cm3/g, respectively. Similarly, the CO2 adsorption capacity of activated hollow carbon microspheres increased with the increasing thickness of the shell layer, and that of AHMCS-2(1) reached 5.54 mmol/g at 0 °C. High specific surface area, high micropore volume, high nitrogen content, and small micropore pore size are favorable for CO2 adsorption by carbon microspheres. The hollow carbon microspheres exhibit high CO2 dynamic adsorption capacity, excellent selective adsorption, and good cyclic stability. Highlights: Nitrogen-rich hollow carbon microspheres with different shell layer thicknesses were prepared using the template method. The thicker shell thickness retains more micropores and nitrogen content. The nitrogen-rich hollow carbon microspheres have high CO2 adsorption performance due to large specific surface area and high nitrogen content. The effect of activation process on the nitrogen-rich hollow carbon microspheres with different shell thicknesses is investigated. [ABSTRACT FROM AUTHOR]