Bioinspired Gradient Covalent Organic Framework Membranes for Ultrafast and Asymmetric Solvent Transport

Abstract

Gradients played a pivotal role in membrane technologies, e.g., osmotic energy conversion, desalination, biomimetic actuation, selective separation and more. In these applications, the compositional gradients are of great relevance for successful function implementation, ranging from solvent separation to smart devices. However, the construction of functional gradient in membranes is still challenging both in scale and directions. Inspired by the specific function‐related, graded porous structures in glomerular filtration membranes, we report here a general approach for constructing gradient covalent organic framework membranes (GCOMx) applying poly (ionic liquid)s as template. With graded distribution of highly porous COF crystals along the membrane, GCOMx exhibited an unprecedented asymmetric solvent transport when applying different membrane sides as the solvent feed surface during filtration, leading to a much‐enhanced flux (10∼18 times) of the “large‐to‐small” pore flow comparing to the reverse direction, verified by hydromechanical theoretical calculations. Upon systematic experiments, GCOMx achieved superior permeance in nonpolar (hexane∼260.45 LMH bar−1) and polar (methanol∼175.93 LMH bar−1) solvents, together with narrow molecular weight cut‐off (MWCO, 472 g mol−1) and molecular weight retention onset (MWRO, <182 g mol−1). Interestingly, GCOMx showed significant filtration performance in simulated kidney dialysis, revealing great potential of GCOMx in bionic applications.This article is protected by copyright. All rights reserved