Ca-Embedded C2N: an efficient adsorbent for CO2 capture.

Carbon dioxide as a greenhouse gas causes severe impacts on the environment, whereas it is also a necessary chemical feedstock that can be converted into carbon-based fuels via electrochemical reduction. To efficiently and reversibly capture CO2, it is important to find novel materials for a good balance between adsorption and desorption. In this study, we performed first-principles calculations and grand canonical Monte Carlo (GCMC) simulations, to systematically study metal-embedded carbon nitride (C2N) nanosheets for CO2 capture. Our first-principles results indicated that Ca atoms can be uniformly trapped in the cavity center of C2N structure, while the transition metals (Sc, Ti, V, Cr, Mn, Fe, Co) are favorably embedded in the sites off the center of the cavity. The determined maximum number of CO2 molecules with strong physisorption showed that Ca-embedded C2N monolayer is the most promising CO2 adsorbent among all considered metal-embedded materials. Moreover, GCMC simulations revealed that at room temperature the gravimetric density for CO2 adsorbed on Ca-embedded C2N reached 50 wt% at 30 bar and 23 wt% at 1 bar, higher than other layered materials, thus providing a satisfactory system for the CO2 capture and utilization.