Water/Vapor Assisted Fabrication of Large‐Area Superprotonic Conductive Covalent Organic Framework Membranes

Abstract Fabrication of large‐area ionic covalent organic framework membranes (iCOMs) remains a grand challenge. Herein, the authors report the liquid water and water vapor‐assisted fabrication of large‐area superprotonic conductive iCOMs. A mixed monomer solution containing 1,3,5‐triformylphloroglucinol (TFP) in 1,4‐dioxane and p‐diaminobenzenesulfonic acid (DABA) in water is first polymerized to obtain a pristine membrane which subsequently underwent crystallization process in mixed vapors containing water vapor. During the polymerization stage, water played a role of a diluting agent, weakening the Coulombic repulsion between sulfonic acid groups. During the crystallization stage, water vapor played a role of a structure‐directing agent to facilitate the formation of highly crystalline, large‐area iCOMs. The resulting membranes achieved a proton conductivity value of 0.76 S cm⁻¹ at 90 °C under 100% relative humidity, which is among the highest ever reported. Using liquid water and water vapor as versatile additives open a novel avenue to the fabrication of large‐area membranes from covalent organic frameworks and other kinds of crystalline organic framework materials.