Vapor/Vapor‐Solid Interfacial Growth of Covalent Organic Framework Membranes on Alumina Hollow Fiber for Advanced Molecular Separation

• Published in: Angewandte Chemie International Edition Vol. 63; no. 32; pp. e202406830 - n/a
• Main Authors: Siow, Wei Jian Samuel, Chong, Jeng Yi, Ong, Jia Hui, Kraft, Markus, Wang, Rong, Xu, Rong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 05.08.2024
• Edition: International ed. in English
• Subjects: Adhesive strength; Alumina; alumina hollow fiber; Aluminum oxide; Chemical synthesis; covalent organic frameworks; Crystallization; Dimethyl sulfoxide; Flow stability; Industrial applications; loose nanofiltration; Membranes; Molecular structure; Molecular weight; Nanofiltration; Nanotechnology; organic solvent nanofiltration; Separation; Substrates; vapor/vapor-solid interfacial growth; Vapors; vapor/vapor-solid interfacial growth; alumina hollow fiber; loose nanofiltration; covalent organic frameworks; organic solvent nanofiltration
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202406830

Covalent organic frameworks (COFs), known for their chemical stability and porous crystalline structure, hold promises as advanced separation membranes. However, fabricating high‐quality COF membranes, particularly on industrial‐preferred hollow fiber substrates, remains challenging. This study introduces a novel vapor/vapor‐solid (V/V−S) method for growing ultrathin crystalline TpPa‐1 COF membranes on the inner lumen surface of alumina hollow fibers (TpPa‐1/Alumina). Through vapor‐phase monomer introduction onto polydopamine‐modified alumina at 170 °C and 1 atm, efficient polymerization and crystallization occur at the confined V−S interface. This enables one‐step growth within 8 h, producing 100 nm thick COF membranes with strong substrate adhesion. TpPa‐1/Alumina exhibits exceptional stability and performance over 80 h in continuous cross‐flow organic solvent nanofiltration (OSN), with methanol permeance of about 200 L m−2 h−1 bar−1 and dye rejection with molecular weight cutoff (MWCO) of approximately 700 Da. Moreover, the versatile V/V−S method synthesizes two additional COF membranes (TpPa2Cl/Alumina and TpHz/Alumina) with different pore sizes and chemical environments. Adjusting the COF membrane thickness between 100–500 nm is achievable easily by varying the growth cycle numbers. Notably, TpPa2Cl/Alumina demonstrates excellent OSN performance in separating the model active pharmaceutical ingredient glycyrrhizic acid (GA) from dimethyl sulfoxide (DMSO), highlighting the method's potential for large‐scale industrial applications. Through vapor/vapor‐solid (V/V−S) interfacial method, in which vapor‐phase monomers were introduced onto polydopamine(PDA)‐modified alumina at 170 °C and 1 atm within 8 h, ultrathin crystalline TpPa‐1 membranes were successfully grown on the inner lumen surface of alumina hollow fibers substrate. The resulting filtration module exhibits exceptional stability and performance in continuous inside‐out cross‐flow organic solvent nanofiltration.