Theoretical Investigations Of Cation-functionalized Graphene Oxide Membranes

The structure and stability of alkali and alkaline earth cation-decorated graphene oxide(M-GO)membranes and their selective permeability to three common organic solvents(toluene,ethanol andacetone)are investigated by density functional theory calculations.For the host M-GO membrane,all cations prefer to be located at the center of the carbon hexagon,partially replacing the sp2 regions isolated within the sp3 C-O matrix of GO sheets.Based on the principle that the delocalization of πconjugated states of sp2 regions determines the cation-πinteraction,a design guide for the fabrication of high-quality M-GO membranes is proposed.Thermodynamic calculation results,consistent with the experimental tests,reveal that the attraction of decorated cations rather than inherent epoxy groups is responsible for the transport process of solvents through M-GO membranes.Acetone and toluene has better permeability than ethanol.While large-scale sp3 C-O matrix has opposite effects on the migration of ethanol,which is the reason of separation of misciblesolvents(C2H5OH/PhCH3)by M-GO membranes.The competition between the two interactions fromcations and epoxy groups is the origin of selective permeability of M-GO membranes for organic solvents.Findings from the study will be helpful to the further design of more M-GO membranes as cost-effective solution nanofilters in chemical separations and drug delivery.