Charge- and Electric-Field-Controlled Switchable Carbon Dioxide Capture and Gas Separation on a C2N Monolayer

The use of advanced materials with a high selectivity and easy regeneration to capture CO2 from a gas mixture is an effective strategy to reduce the greenhouse effect. In this study, we report a comprehensive investigation of CO2, N2, CH4, and H2 adsorption on a C2N monolayer by using DFT calculations. We find that CO2 is adsorbed weakly on a neutral C2N monolayer, and the interaction between CO2 and C2N can be enhanced considerably by applying a negative charge or an external electric field to C2N. Moreover, once the charge state/electric field is switched off, CO2 is released spontaneously from the C2N. However, in contrast to the adsorption of CO2, the interaction between N2/CH4/H2 and C2N is physisorption under all of the above conditions. In all, our study demonstrates that the C2N monolayer can be used as an excellent material for highly selective and reversible CO2 capture and gas separation through the strategy of switching on/off its charge state/electric field. In addition, as a 2D material, the C2N monolayer possesses a narrow band gap (1.70 eV) that ensures that the application of a charge/electric field can be realized easily experimentally by electrochemical methods.