Current challenges and approaches for energy-efficient ion-selective 2D graphene-based channels

Atomically thin two-dimensional (2D) materials are highly regarded for contemporary separation challenges such as desalination, especially in designing membranes with the potential to overcome the classical permeance-selectivity trade-off challenge, however, critical challenges remain. Graphene oxide (GO)-based membranes have low retention for monovalent ions as instability in aqueous media has yet to be adequately resolved and impacts their widespread application. Beyond GO, other 2D materials such as MoS2 have promising selectivity and permeance properties but are severely hindered by their ability to be scalably produced. By taking inspiration from biological ion channels, a design philosophy can be developed realizing efficient ion selectivity through introducing engineered nanochannel chemistry. Development of 2D material membranes for complex ion separation applications requires looking beyond simple steric effects for discriminating between ions and toward favorable chemical environments for enhancing or hindering ion transport.