Tunable anion transport and the chemical transistor effect in functionalized graphene oxide membranes

Abstract Selective anion transport is essential for energy conversion, water purification, and electrochemical systems, yet achieving precise ion selectivity in membranes remains a challenge. Here, we present an amino-functionalized graphene oxide (am-GO) membrane that enables tunable anion transport through nanochannels. Using a combined experimental and computational approach, we consider the three stages of ionic transport—absorption, diffusion, and desorption—to reveal that Cl− selectively diffuses through nanochannels, while NO3 −, SO4 2−, and PO4 3− are excluded. In ionic mixtures, the chemical transistor effect emerges, where Cl− pulls water from NO3 − hydration shell, enhancing its mobility, while SO4 2− and PO4 3− remain excluded due to size constraints. This mechanism enables precisely regulated Cl− and NO3 − transport, with ultrahigh rejection rates of 99.99% for SO4 2− and PO4 3−, even in complex ionic environments. The am-GO exhibits stability and anion-hopping mechanisms, making it a versatile platform for anion exchange membranes in electrolysis, energy storage, and environmental applications.