Tailoring the Microenvironments of Dual‐Confinement COF Nanofluidics for High‐Throughput and Selective Ion Transport

ABSTRACT Nanofluidic channels provide an ideal platform for mimicking the remarkable ion selectivity and permeability of biological ion channels, but current architectures are limited by mismatched pore dimensions, low surface charge, and insufficient functionalization, resulting in subpar ion selectivity and flux. Here, we present rationally designed covalent organic framework (COF) nanofluidics with dual‐confinement channels. By precisely modulating the building block length (from 0.58 to 1.22 nm) and spatially programmable functional group density (from −0.13 to −0.79 µC cm −2 ), we synergistically integrate geometric confinement with affinity interactions to tailor the channel microenvironments. The optimized COF nanofluidics achieved exceptional cation selectivity, enhanced from 0.80 to 0.95, while maintaining high ion throughput that increased from 1.93 × 10 14 to 5.12 × 10 14 ions s −1 . As a result, the COF nanofluidics‐based generator delivers an impressive output power density of 11.3 W m −2 by using natural seawater, capable of continuously powering various electronics. Molecular dynamics simulations reveal the dual‐confinement COF nanofluidics with nanoscale channel geometry and strong affinity interactions facilitate an ion‐hopping process that boosts ion selectivity by 4‐fold and ion throughput by 2.5‐fold compared to unoptimized counterparts. This work provides design principles for developing dual‐confinement nanofluidics, showing potential in desalination and ion separation.