Effect of Heat Treatment on the Nitrogen Content and Its Role on the CO2 Adsorption Capacity of Highly Ordered Mesoporous Carbon Nitride

Mesoporous carbon nitrides (MCN) with rod shaped morphology and tunable nitrogen contents have been synthesized via calcination free method using ethanol-washed mesoporous SBA-15 as templates at different carbonization temperatures. Carbon tetrachloride (CTC) and ethylenediamine (EDA) were used as the sources of carbon and nitrogen respectively. The resulting MCN materials were characterized with low and high angle power XRD, N2 adsorption, HR-SEM, HR-TEM, CHN elemental analysis, XPS and. XANES techniques. It is observed that the carbonization temperature plays a critical role in controlling not only the crystallinity but also the nitrogen content and the textural parameters of the samples including specific surface area and specific pore volume. Nitrogen content of MCN decreases with the concomitant increase of specific surface area and specific pore volume as well as the crystallinity of the samples as the carbonization temperature is increased. The results also reveal that the structural order of the materials is retained even after the heat treatment at temperature upto 900 °C with a significant reduction of the N content but the structure is partially damaged at 1000 °C. It is also found that the CO2 adsorption capacity of these materials is not only dependent on the textural parameters but also on the nitrogen content. The MCN prepared at 900 °C, which has optimum BET surface area and nitrogen content, registers the CO2 adsorption capacity of 20.1 mmol/g at 273K and 30 bar, which is much higher than that of mesoporous silica, MCN-1, activated carbon and multi-walled carbon nanotubes.