Gas Transport across Carbon Nitride Nanopores: A Comparison of van der Waals Functionals against the Random-Phase Approximation

C2N is an ordered two-dimensional carbon nitride with a high density (1.7 × 1014 cm–2) of 3.1 Å-sized nanopores, making it promising for high-flux gas sieving energy-efficient He and H2 purification. Herein, we discuss the accurate calculation potential energy surfaces He, H2, N2, CO2 across to characterize gas-sieving C2N. We compare surface derived from density-functional theory calculations using five commonly used van der Waals (vdW) approximations. While all functionals point that nanopore yields He/N2 H2/N2 selectivities over 1000, adsorption energies barriers vary remarkably depending on approximation chosen. To make progress, against results adiabatic connection fluctuation dissipation theory, random-phase approximation, known be in capturing vdW interactions. The comparison indicates interaction less functional theory. On other hand, more empirical corrections work reasonably well, finding also confirm another lattice, poly(triazine imide). Overall, recommend these screening materials separation, but comparing higher-order approaches when dealing different materials.