High-Flux Vertically Aligned 2D Covalent Organic Framework Membrane with Enhanced Hydrogen Separation

Abstract

In this study, we propose a new concept of vertically aligned 2D covalent organic framework (COF) layers forming a membrane for efficient gas separation on the basis of precise size exclusion. Gas transport takes place through the COF interlayer space (typically 0.3-0.4 nm) rather than through the nanometer-sized pore apertures. Construction of such a unique membrane architecture was implemented via <i>in situ</i> oriented growth of 2D COFs inside a skeleton of vertically aligned CoAl-layered double hydroxide (LDH) nanosheets. The resultant vertical COF-LZU1 membrane exhibits a high H₂ permeance of ∼3600 GPU together with a desirable separation selectivity for gas mixtures such as H₂/CO₂ (31.6) and H₂/CH₄ (29.5), thus surpassing the 2008 Robeson upper bounds. The universality of this approach was demonstrated by successfully producing two types of high-quality vertical COF membranes with superior performance as well as outstanding running stability.