Abstract: A poly(ionic liquid) was prepared from an ionic liquid monomer that was obtained by the reaction of 1-vinylimidazole, 4-vinyl-benzene chloride with 2,6-di-tert-butyl-4-methylphenol. The poly(ionic liquid) was mixed with K₃Fe(CN)₆ and a 5 nm silica colloidal sol, carbonized at 900℃ for 4 h, and sequentially treated with HNO₃ and NaOH to remove the iron and silica to obtain nitrogen-doped graphitic carbon nanocapsules. The iron and silica acted as a graphitization catalyst and template, respectively. The nitrogen-doped graphitic carbon nanocapsules have a diameter of 50 nm and a wall thickness of 6 nm and have a high adsorption capacity and good recyclability for CO₂ capture. The addition of SiO₂ nanoparticles in the synthesis significantly increased the specific surface area from 100.4 to 865.7 m²·g^-1 and the CO₂ adsorption capacity from 0.76 to 2.14 mmol·g^-1.