▎ 摘　　要

NOVELTY - The semi-permeable membrane comprises two two-dimensional (2D) heterostructure layers. A polyelectrolyte layer is positioned between two 2D heterostructure layers. The semi-permeable membrane is formed by a self-assembly of two 2D heterostructure layers and the polyelectrolyte layer. Each 2D heterostructure layer and polyelectrolyte layer are bonded to one another via electrostatic interactions, hydrogen bonds, van der Waals interaction, hydrophobic interactions, or a combination. Two 2D heterostructure layers are formed in a layer-by-layer assembly. The 2D heterostructure layer includes graphene, graphene-oxide, hexagonal boron nitride, transition metal dichalcogenides, 2D transition metal carbides, 2D transition metal nitrides, 2D metal oxides, or a combination. The polyelectrolyte layer includes proteins, polybases, polyacids, polynucleotides, polysaccharides, or a combination. The water flux through the membrane is controlled by changes in internal osmotic pressure within membrane. USE - Semi-permeable membrane e.g. nanoporous graphene (NG) membrane and lamellar graphene oxide (GO) membrane, for use in an aqueous environment. ADVANTAGE - The semi-permeable membrane has improved permeability and selectivity for various gas mixtures and shows barrier properties for ions. The membrane exhibits a salt rejection of greater than or equal to 100% while allowing rapid water transport. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing a membrane, which involves mixing a 2D heterostructure solution and a polyelectrolyte solution to form a mixture, vacuum filtering the mixture onto a substrate to form the membrane, centrifuging the colloidal mixture to separate particles from the colloidal mixture, and drying the membrane following the vacuum filtering. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of a sandwich configuration of a membrane.