Efficient enhancement of CO2 separation and capture of the T-C3N2 membranes with modulations of strain, charge, and their synergistic effect

The effective separation and capture of CO2 over C2H2 and CH4 via T-C3N2 monolayer membranes modulated by strain, charge, and their synergistic effect was realized by using molecular dynamics simulations and density functional theory calculations. The strained T-C3N2 monolayer exhibits high CO2 permeability of 2.15 × 107 and 2.32 × 107 GPU at 300 K in the CO2/C2H2 and CO2/CH4 separation. The introduction of negative charges is a promising approach for improving CO2 separation performance due to the breaking of trade-off effects, that is, not only the CO2 permeability is enhanced to (2.94–3.07) ×107 GPU but also the selectivity of CO2 relative to C2H2 and CH4 is improved to 4.40 × 1033 and 2.82 × 1022, higher by 1016 and 107 orders of magnitude compared to pure T-C3N2. The synergistic effects of strain and negative charges also effectively enhance CO2 separation performance, and the effectiveness surpasses strain modulation but is slightly weaker than individual charge modulation. The adsorption strength of CO2 on the T-C3N2 surface can be significantly increased by modulation of negative charges. Moreover, the CO2 capture/release on/from the T-C3N2 monolayer could be realized by modulating the process of injection/removal of negative charges. The CO2 uptake capacity reaches 5.26 × 1014 cm−2, which is superior to that of other membrane materials. The demonstrated enhancement of the CO2 separation and capture performance by modulations of strain, charge, and their synergistic effect suggests broad prospects for the applications of the T-C3N2 membranes in the efficient separation and capture of CO2 from low-carbon hydrocarbon gases and carbon capture.