pH-dependent water permeability switching and its memory in MoS2 membranes

Intelligent transport of molecular species across different barriers is critical for various biological functions and is achieved through the unique properties of biological membranes1-4. An essential feature of intelligent transport is the ability to adapt to different external and internal conditions and also the ability to memorise the previous state5. In biological systems, the most common form of such intelligence is expressed as hysteresis6. Despite numerous advances made over previous decades on smart membranes, it is still a challenge for a synthetic membrane to display stable hysteretic behaviour for molecular transport7-11. Here we show the memory effects and stimuli regulated transport of molecules through an intelligent phase changing MoS2 membrane in response to external pH. We show that water and ion permeation through 1T′ MoS2 membranes follows a pH dependent hysteresis with a permeation rate that switches by a few orders of magnitude. We establish that this phenomenon is unique to the 1T′ phase of MoS2 due to the presence of surface charge and exchangeable ions on the surface. We further demonstrate the potential application of this phenomenon in autonomous wound infection monitoring and pH-dependent nanofiltration. Our work significantly deepens understanding of the mechanism of water transport at the nanoscale and opens an avenue for developing intelligent membranes.