Biomimetic Janus MXene membrane with bidirectional ion permselectivity for enhanced osmotic effects and iontronic logic control.

Osmotic efficiency is fundamentally governed by the balance between membrane ion selectivity and permeability, a challenge central to both biological signal transmission and sustainable energy conversion. Conventional membranes are constrained to unidirectional transport of either cations or anions, severely limiting their versatility and performance. Inspired by the chloride voltage-gated channel 5 (ClC-5), we engineered a biomimetic Janus NP-MXene membrane featuring subnanochannels (~6.0 angstrom) and exceptional structural integrity, enabling controlled, simultaneous Na/Cl transport with unprecedented permselectivity. Under a 50-fold salinity gradient, the NP-MXene membrane achieved a record power density of 85.1 watts per square meter and an osmotic potential of 181.5 millivolts, the highest reported for a single device. Harnessing ion-specific signals from multi-ion transport, we further demonstrated an iontronic transistor capable of modulating ion flow by salinity gradients, eliminating the need for external gate voltage. This advance enables encoded signals and robotic control for advanced human-machine interfaces. The scalable fabrication of nanofluidic channels facilitates high-performance iontronics for efficient energy-information flow.