Synergistic effect of charge and strain engineering on porous g-C9N7 nanosheets for highly controllable CO2 capture and separation

Abstract

Efficient CO2 capture and separation, such as from natural gas, biogas, and landfill gas, is highly desirable to maximize the use of energy and alleviate carbon emission and greenhouse effect. A novel approach of charge/strain-regulated gas capture and separation has been proposed to offer the advantages of reversibility and controllable kinetics. We demonstrated the highly controllable CO2 capture and separation from CO2/CH4 on porous g-C9N7 nanosheets with varying charge densities and strains using molecular dynamics (MD) simulations and first-principle density function theory (DFT) calculations. The remarkable CO2 permeance up to 5.94 × 107 GPU can be achieved by charge engineering, such as through the strategies of electrochemical methods. A tunable CO2 separation performance was exhibited under the condition of tensile strain. The permeance of CO2 was found to increase with increasing the applied tensile strain, and the maximum permeance was 3.61 × 107 GPU with 7.5% strained g-C9N7 membrane. More interestingly, a promising approach for combining a charged state with the strain engineering was explored to investigate the synergistic effect. Under conditions of 1 e- negative charge and 3% tensile strain on g-C9N7 membrane, the CO2 permeance reached 3.18 × 107 GPU, which was 9 times higher than only with adding 1 e-, and 8 times higher than only applying 3% strain. Additionally, the temperature effect indicated that the g-C9N7 membrane can be served as an excellent candidate for CO2/CH4 separation at ambient conditions. These results provide useful guidance for developing advanced materials with highly controllable CO2 capture and separation properties.