Collective Fluid Coupling in Ultrathin Covalent Organic Framework Membranes for High-Performance Electrokinetic Energy Harvesting.

Abstract

Nanofluidic membranes hold promise for hydroelectric energy harvesting, but their output power is often limited by high fluidic impedance. Here, we fabricate ultrathin covalent organic framework (COF) membranes with AA-stacked, regular nanopore arrays. These membranes exhibit high fluid permeability exceeding 107 L m-2 h-1 bar-1, and record electrokinetic outputs with a streaming current density of 4.7 kA m-2 bar-1 and a power density of 12.8 W m-2 bar-1 in 1 M KCl. The high performance arises from the combination of ultrathin nature and collective interpore transport. Theoretical simulations reveal that the reduced interpore distance induces strong collective hydrodynamic coupling, which straightens streamlines, mitigates near-wall velocity dissipation, lowers fluidic resistance, and enhances net spatial charge density. We further demonstrate a heart-beat-driven nanofluidic generator with high sensitivity and stability. Crucially, the membrane maintains robust energy conversion efficiency even when the active area is scaled up by over 3 orders of magnitude to device-relevant dimensions. This work establishes densely packed COFs as a scalable platform for overcoming fluidic-impedance limitations in next-generation micropower devices.