Regulating CO₂ adsorption performance of lychee seed-based porous carbon materials: Insights into oxygen groups and...

Herein, porous carbon materials rich in oxygen (O)-containing functional groups and with abundant micropores were synthesized by carbonizing lychee seeds activated with various activators at a relatively low temperature of 600 °C. The incorporation of potassium and sodium salts during activation effectively modulated both the surface O functionalities and the microporous structure of the resulting porous carbon materials. The influence of these characteristics on CO₂ adsorption performance was systematically investigated. A multiple linear regression model was developed to evaluate the impact of key factors including cumulative pore volumes in the pore size range of 5-7 Å (V_5-7 Å), 0-10 Å (V_0-10 Å), and 0-20 Å (V_0-20 Å), total pore volume (V_T), and the contents of C=OOH and C-OH groups on the CO₂ adsorption capacity of the carbon materials at 1 bar and 25 °C. Results revealed that the C=OOH content is the most significant factor affecting CO₂ uptake, while C-OH content and V_0-20 Å also play important secondary roles. Notably, the LS-KOH-600 sample exhibited a high CO₂ adsorption capacity, reaching 5 mmol/g at 25 °C and 7.15 mmol/g at 0 °C (1 bar). Furthermore, LS-KOH-600 demonstrated excellent CO₂/N₂ selectivity (29.9) and good cyclic stability under simulated flue gas conditions.