Study on CO2 Adsorption and Permeance of Porous Carbon and Nitrogen Membranes Co-regulated by Charge and Strain

Abstract

In order to capture and separate CO2 effectively, a novel method of controlling gas permeance by charge and strain is proposed, which has the superiority of controlled dynamic. The effects of porous C9N7 nanosheets on CO2 capture and permeability under different charge quantities and strains were analysed by molecular dynamics (MD) simulations and first-principles density function (DFT) calculations. The molecular permeability of CO2 can be as high as 5.9 × 107 GPU (CO2/CH4 separation) through 5 e- charge regulation. In addition, CO2 permeability increased with the increase of tensile strain, and the maximum permeability of 9% stretched C9N7 membrane is 3.6 × 107 GPU. On this basis, the method of combining negative charge and tensile strain was adopted to study the synergic effect. Under the condition of negative charge of 1 e- and tensile strain of 3%, CO2 permeability (CO2/CH4 separation) reached 3.2 × 107 GPU, which was 8 times of CO2 permeability when only 3% strain was added and 9 times of CO2 permeability when only 1 e- was added. Additionally, under the circumstance of negative charge of 5 e-, the CO2 obtained extra electrons -0.0666 e compared with natural C9N7 membrane. These results provide theoretical guidance for the development of highly controllable materials with CO2 capture and separation.