Mesoporous carbon nitride supported MgO for enhanced CO₂ capture

The growing concern about the environmental consequences of anthropogenic CO₂ emissions significantly stimulated the research of low-cost, efficient, and recyclable solid adsorbents for CO₂ capture. In this work, a series of MgO-supported mesoporous carbon nitride adsorbents with different MgO contents (xMgO/MCN) was prepared using a facile process. The obtained materials were tested for CO₂ capture from 10 vol% CO₂ mixture gas with N₂ using a fixed bed adsorber at atmospheric pressure. At 25 ºC, the bare MCN support and unsupported MgO samples demonstrated CO₂ capture capacities of 0.99, and 0.74 mmol g^-1, respectively, which were lower than those of the xMgO/MCN composites.The incorporation of MgO into the MCN improved the CO₂ uptake, and the 20MgO/MCN exhibited the highest CO₂ capture capacity of 1.15 mmol g^-1 at 25 °C. The improved performance of the 20MgO/MCN nanohybrid can be possibly assigned to the presence of high content of highly dispersed MgO NPs along with its improved textural properties in terms of high specific surface area (215 m²g^-1), large pore volume (0.22 cm³g^-1), and abundant mesoporous structure. The efffects of temperature and CO₂ flow rate were also investigated on the CO₂ capture performance of 20MgO/MCN. Temperature was found to have a negative influence on the CO₂ capture capacity of the 20MgO/MCN, which decreased from 1.15 to 0.65 mmol g^-1with temperature rise from 25 C to 150º C, due to the endothermicity of the process. Similarly, the capture capacity decreased from 1.15 to 0.54 mmol g^-1 with the increase of the flow rate from 50 to 200 ml minute^-1 respectively. Importantly, 20MgO/MCN showed excellent reusability with consistent CO₂ capture capacity over five sequential sorption-desorption cycles, suggesting its suitability for the practical capture of CO₂.