On the Mechanism Responsible of the Varying Adsorption Affinities of CO2, N2 and H2O on Graphtriyne Membranes

Deformation Density based Energy Decomposition Analysis (DD-EDA) of the interaction energy between CO2, N2, and H2O and graphtriyne membranes was performed at the DFT-D3 level to elucidate the energy components responsible for the differences in adsorption affinity. Previous explanations at a qualitative level were based on electric dipole and polarizability scales. Surprisingly, neither electrostatic nor polarization interactions primarily account for CO2’s strongest adsorption affinity to a monolayer membrane. Instead, Pauli repulsion governs the adsorption affinity, with CO2 experiencing the lowest Pauli repulsion energy, not showing the more negative polarization or electrostatic energies. The stability of these three molecules within a trilayer membrane follows the same order as in a monolayer. However, in this case, CO2 exhibits the highest Pauli repulsion energy, which is largely offset by its more negative polarization and electrostatic energies. This variation can be attributed to the distinct trends observed in the energy-versus-distance profiles of these gases with a monolayer membrane. These preliminary results, derived from static simulations, should be further validated against those obtained from dynamic simulations.