Razi University

of their atomic-scale thickness, tunable pore geometry, and controllable pore-edge chemistry. In thisstudy, three nanoporous two-dimensional membranes, namely graphene, BC?, and hexagonal boronnitride (h-BN), were comparatively investigated under asymmetric functionalization, in which fluorineatoms were introduced on one side of the membrane and amine (NH?) groups on the opposite side.Density functional theory (DFT) calculations were performed at the B3LYP/6-31G* level with Grimmedispersion correction. The influence of membrane composition and asymmetric functionalization on theelectronic environment of the nanopores was examined using HOMO/LUMO, DOS/PDOS, molecularelectrostatic potential, NBO, dipole moment, deformation density, ELF/LOL, QTAIM, and NCI/RDGanalyses. Gas tra  ort of He, H?, and N? was further investigated using single-point energy profiles,from which permeation energy barriers, permeance, and selectivity were evaluated.The results demonstrated that asymmetric F/NH? functionalization generated electronicallynonequivalent environments around the nanopores in all three membranes, although the magnitude andnature of this effect strongly depended on the substrate. Functionalized h-BN exhibited the highestoverall polarity, whereas BC? provided a more balanced combination of electronic heterogeneity andstructural characteristics. The permeation energy profiles showed substantially more favorable tra  ortpathways for He and H? than for N?. Molecular orientation was also found to be an important sievingfactor, particularly for N?, whose parallel orientation produced the highest permeation barriers. Amongthe investigated membranes, functionalized BC? exhibited the lowest permeation barriers and thehighest permeance for the light gases while effectively restricting N? tra  ort, particularly in its parallelorientation. Although functionalized h-BN provided higher selectivity for some separations, its largerenergy barriers significantly reduced gas tra  ort. Overall, F/NH?-functionalized BC? provided themost favorable balance between permeance and selectivity and was identified as the most promisingmembrane for molecular sieving of the investigated light gases.