Effect of Nitrogen and Oxygen Functional Groups on Bio-Based Porous Carbon Modified Using Activation Modification Treatment to Improve CO₂ Adsorption Performance

This study explores the role of nitrogen and oxygen contents on the surface of modified coconut shell porous carbon to improve its physicochemical properties thus increase CO₂ adsorption capacity. The synthesis of porous carbon was performed using an activation modification method at low temperature (200°C) followed by chemical activation to enhance surface properties of porous carbon. In this study, the surface properties of porous carbon were modified using several types of nitrogen-containing functional groups, such as urea, melamine and amine groups (monoethanolamine [MEA] and 2-(methylamino)ethanol [MAE]). Changes in the surface morphology of the modified porous carbon were characterised using several analytical techniques, including Brunauer–Emmett–Teller (BET) surface area, surface morphology, elemental composition analysis and Raman spectroscopy. The adsorption performance of the modified porous carbon was measured using packed-bed CO₂ adsorption under low-pressure conditions. Subsequently, the highest breakthrough time and CO₂ adsorption capacity values were compared. The analysis of pore size distribution curves confirmed the existence of a combination of micropores, mesopores and a small amount of macropores in all modified porous carbon samples. As expected, the results show that all modified porous carbon samples showed increased breakthrough time and CO₂ adsorption capacity compared to coconut shell activated carbon (CS). Among the modified activated carbon, CS-MAE produced the highest breakthrough time (27 min) and CO₂ adsorption capacity (1.48 mmol/g). Finally, the experiment results from multiple adsorption–desorption cycles show good regeneration performance of CS-MAE. This finding highlights the feasibility of using CS-MAE as a capturing agent for CO₂ adsorption.