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

Abstract

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.