Large‐Area Soluble Covalent Organic Framework Oligomer Coating for Organic Solution Nanofiltration Membranes

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-01, Vol.20 (4), p.e2305613-n/a
• Main Authors: Yu, Huiting, Guan, Jiayu, Chen, Yaohan, Sun, Yuxuan, Zhou, Shengyang, Zheng, Jifu, Zhang, Qifeng, Li, Shenghai, Zhang, Suobo
• Format: Article
• Language: English
• Subjects: coating; covalent organic framework oligomers; Cross flow; Crystal growth; Liquid phases; Membranes; Nanofiltration; Oligomers; organic solution nanofiltration; Polyether ether ketones; solution processing; Solvents; Thin films; thin‐film composite membranes; Ultrafiltration
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202305613

Covalent organic frameworks (COFs) are a family of engaging membrane materials for molecular separation, which remain challenging to fabricate in the form of thin‐film composite membranes due to slow crystal growth and insoluble powder. Here, an additive approach is presented to construct COF‐based thin‐film composite membranes in 10 min via COF oligomer coating onto poly(ether ether ketone) (PEEK）ultrafiltration membranes. By the virtue of ultra‐thin liquid phase and liquid‐solid interface‐confined assembly, the COF oligomers are fast stacked up and grow along the interface with the solvent evaporation. Benefiting from the low out‐plane resistance of COFs, COF@PEEK composite membranes exhibit high solvent permeances in a negative correlation with solvent viscosity. The well‐defined pore structures enable high molecular sieving ability (Mw = 300 g mol−1). Besides, the COF@PEEK composite membranes possess excellent mechanical integrities and steadily operate for over 150 h in the condition of high‐pressure cross flow. This work not only exemplifies the high‐efficiency and scale‐up preparation of COF‐based thin‐film composite membranes but also provides a new strategy for COF membrane processing. Limited by the insoluble natures, covalent organic framework (COF) membrane processing requires hard conditions and much time. A new approach to quickly prepare COF‐based thin‐film composite membranes using simple COF oligomer coating and confined‐interface growth is designed. A crystalline COF film fast forms in 10 min and exhibits excellent high permeance and rejection.