Constructing Nitrogen-Rich Microporous Carbon through a One-Step Molten Salt Method for Carbon Dioxide Capture and Separation

The advancement of highly efficient and economically viable CO2 capture technologies has emerged as a vital measure in the pursuit of global emission reduction targets. In this study, nitrogen-rich microporous carbon materials (NCTs) were successfully synthesized via a one-step molten salt polycondensation and carbonization method which was used as an adsorbent for CO2 capture. Triglycidylisocyanurate and dicyandiamide were used as precursors, while potassium citrate served as both a template and an activator. By adjustment of the molten salt ratio and carbonization temperature, the pore structure and nitrogen doping level were effectively optimized. The resulting NCT-650-M exhibited excellent structural properties, including a high nitrogen content (13.46 wt %), a substantial pore volume (0.65 cm3 g–1), and a large specific surface area (1257.1 m2 g–1). Subsequently, the CO2 adsorption performance was evaluated using three different methods: thermogravimetric static adsorption, CO2 fixed-bed adsorption, and CO2 adsorption isotherms, which revealed a CO2 uptake capacity of 4.19 mmol g–1 at 25 °C and 1 bar. Moreover, exceptional adsorption selectivity and robust cyclic stability in CO2/N2, CO2/CH4, and CO2/O2 separation systems were accomplished, complemented by a detailed investigation into the influence of water vapor under controlled humidity conditions on the CO2 adsorption performance. The mechanisms of CO2 adsorption were thoroughly investigated, revealing the key factors that contribute to its exceptional performance. These findings highlight the significant potential of NCTs for practical applications in CO2 capture and separation.