Theoretical permeability of membrane is inversely proportional to its thickness, which indicates ultrathin membranes will be extremely permeable. Inspired by the atomic thickness of graphene, herein we report a four-layered graphene membrane with a thickness of about 2 nm. The ultrathin membrane is facilely fabricated by directly punching a complete graphene sheet through selective removal of some carbon atoms with metal oxide nanoparticles at high temperature. Their perpendicular pore channels spanning the whole thickness could, to a great extent, reduce hydrodynamic resistance for water transport. Experimental tests have revealed a flux of up to 4600 L m-2 h-1 of the membranes with a pore size of 50 nm and pore density of 1.0 × 107 cm-2 at a pressure of 0.2 bar. This flux is 40-400 times higher than those of conventional ceramic membranes and track-etched membranes. The enhancement in water permeance is attributed to their atomic thickness and straight pore channels. High selectivity is also evidenced by selective separation of nanospheres with their narrowly distributed pores. These atomic-thin graphene membranes, in view of their outstanding permeability and selectivity, possess great potential as future advanced membranes and may inspire the design and development of other innovative membranes.
Keywords: atomic thickness; graphene; high permeability; membrane; selectivity.