Molecular-level D-A interaction engineering for high-efficiency photoelectric nanofluidic ion transport

Inspired by biological light-driven ion transport, photoelectric nanofluidic systems offer a promising route toward intelligent ion regulation and signal transduction. Unlike traditional semiconductors constrained by rigid band structures, donor-acceptor (D-A) materials present superior tunability and photoelectric conversion efficiency. Here, we demonstrate molecular-level engineering of D-A interactions in covalent organic frameworks (COFs) to achieve efficient light-enhanced nanofluidic ion transport. By systematically varying the electron-donating and electron-accepting strengths of the building blocks, we designed two D-A COFs, namely D-A PCOF and D-A MCOF, with gradually modulated surface charge density. Among them, D-A PCOF, which integrates strong acceptor and donor units into a single crystalline framework, displays optimized optoelectronic properties. This structural and electronic synergy facilitates efficient photoinduced charge separation and directional carrier migration, resulting in significantly enhanced selective ion transport. When applied in osmotic energy conversion, the D-A PCOF membrane delivers a remarkable 74% increase in output power under illumination across a 50-fold salinity gradient and achieves a high-power density of 83.4 W m^-2 under a 500-fold gradient. This work underscores charge microenvironment engineering as a powerful strategy for designing high-performance photo-responsive nanofluidic membranes.