Abstract

Two distinct types of nitrogen-enriched nanoporous carbon were synthesized from polybenzoxazine (PBZ), using dicyandiamide (DCDA) as a thermally decomposable template and sodium chloride (NaCl) as a salt template to improve ultramicroporosity, specific surface area, pore volume, and nitrogen functionalities, along with CO<inf>2</inf> activation. The nanoporous carbon prepared with the DCDA template showed different levels of nitrogen functionalities compared to that made with the NaCl template. The resulting materials exhibited significant ultramicroporosity, a high specific surface area (up to 1521 m² g^–1), pore volume (up to 0.64 cm³ g^–1), and nitrogen content (up to 5.05 % wt.). X-ray photoelectron spectroscopy analysis revealed that DCDA-derived nanoporous carbon contained a higher proportion of graphitic-N and pyridinic-N. In contrast, NaCl-templated nanoporous carbon was rich in pyridinic and pyrrolic nitrogen. These nitrogen functionalities, especially pyridinic-N, combined with ultramicropores, synergistically enhanced CO<inf>2</inf> capture through Lewis acid-base interactions. Response surface methodology was employed to investigate the interactive effects among key structural and chemical variables, confirming that ultramicroporosity, specific surface area, and pyridinic-N collectively contributed to CO<inf>2</inf> capture. The sample derived from 10 % wt. NaCl (10-NaCl-A) exhibited the highest CO<inf>2</inf> uptake measured at 30 °C: 5.71 mmol g^–1 (1 bar), 27.23 mmol g^–1 (40 bar), and 31.25 mmol g^–1 (45 bar). Additionally, it demonstrated excellent recyclability, maintaining 96.6 % of its initial CO<inf>2</inf> adsorption capacity after eight cycles. These findings highlight the significance of nitrogen configuration and pore design in enhancing CO<inf>2</inf> adsorption performance.