Bionic Ion Pumps: Triazine-Based Covalent Organic Framework Nanofluidics for Photo-Induced Ion Transport and Nanofluidic Energy Conversion

Nanofluidic ion transport, traditionally governed by charge-induced electrical double layers (EDLs), has enabled diverse applications in energy conversion, sensing, and ion sieving. However, such transport is intrinsically passive as it relies on static interface charges. Inspired by biological ion channels, which utilize dynamic interface charges to drive active ion pumping in chloroplast thylakoid membranes during photosynthesis, we demonstrate a photo-induced, active bionic ion transport system. This is achieved using an ultrathin nanofluidic membrane constructed from triazine-based covalent organic frameworks (COFs). The nanofluidic membrane is fabricated via confined interface polymerization, yielding a free-standing, large-area, ultrathin (∼40 nm) structure with robust mechanical properties (Young's modulus ∼1.9 GPa). Light induces a dynamic interface charge change and a photoelectric effect that break ionic thermodynamic equilibrium, thereby stimulating active ion transport with ultrafast sensitivity (response time <1 s) and a high ion transport rate (∼6 × 10⁶ ions/s) and achieving a nanofluidic electrokinetic energy conversion (power density >1 mW/m²). The mechanisms underlying dynamic ion transport and active ion pumping are systematically elucidated and experimentally validated. This work demonstrates the potential of COF membranes for applications in areas such as ionic photodetectors, energy conversion systems, field-effect nanofluidic devices, and desalination processes.