Ultrathin graphene-based membrane with precise molecular sieving and ultrafast solvent permeation

TL;DR

This paper presents ultrathin graphene oxide membranes with precise molecular sieving and ultrafast permeation for both water and organic solvents, enabling high rejection rates in organic solvent nanofiltration.

Contribution

The study demonstrates the fabrication of ultrathin GO membranes with interconnected pinholes and short channels, achieving fast permeation of organic solvents and high rejection rates, expanding GO membrane applications.

Findings

Ultrathin GO membranes (~10 nm) allow fast permeation of water and organic solvents.

Organic solvent permeation decays exponentially with increasing membrane thickness.

>99.9% rejection of organic dyes in methanol achieved.

Abstract

Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation rates. However, the membranes' use has been limited mostly to aqueous solutions because GO membranes appear to be impermeable to organic solvents, a phenomenon not fully understood yet. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (2D) capillaries made from flakes with large sizes of ~ 10-20 micron. Without sacrificing their sieving characteristics, such membranes can be made exceptionally thin, down to ~ 10 nm, which translates into fast permeation of not only water but also organic solvents. We attribute the organic solvent permeation and sieving properties of ultrathin GO laminates to the presence of randomly distributed pinholes that are interconnected by short graphene channels with a width of 1 nm. With increasing the membrane thickness, the organic solvent permeation rates decay exponentially but water continues to permeate fast, in agreement with previous reports. The application potential of our ultrathin laminates for organic-solvent nanofiltration is demonstrated by showing >99.9% rejection of various organic dyes with small molecular weights dissolved in methanol. Our work significantly expands possibilities for the use of GO membranes in purification, filtration and related technologies.