Strain-controlled carbon nitride: A continuously tunable membrane for gas separation

Introducing strain during membrane separation is an excellent strategy for achieving controllable separation performance. Herein, a continuously tunable carbon nitride (CN) membrane was investigated under the tensile strain of 0.00–10.00% for gas separation by using density functional theory (DFT) and molecular dynamic (MD) simulations. The DFT calculations showed that CN membrane exhibited a decreasing gas diffusion energy barrier and increasing diffusion rate and permeance with the increase in applied tensile strain. The "open" and "closed" states for gas molecules penetrating CN membrane can thus be regulated by the controlled strain. The transition points of "open" and "closed" states for H2, CO2, CO, N2, and CH4, based on their permeances, occurred under 0.00%, 0.41%, 2.17%, 2.78%, and 8.62% strains, respectively. The results of MD simulations match well with the DFT results. Thus, CN membrane can be performed for the continuous gas separation of CH4, N2, CO, CO2, and H2 from mixtures under controlled strain. This work highlighted strain-controlled carbon nitride as a potential continuously tunable membrane for light gas separation, and opened a promising avenue for the screening of industrial gas separation membranes.