Triphenylamine-based COFs composite membrane fabricated through oligomer-triggered interfacial polymerization

Covalent organic frameworks (COFs) are attractive innovative crystalline porous materials that have immense potential for the production of high-performance nanofiltration membranes. Although the conventional water-organic interfacial polymerization process has been broadly applied to fabricate COFs composite membranes on polymeric substrates, it cannot be applicable for COFs constructed by poorly water-soluble aromatic amine monomers. Herein, we report the fabrication of triphenylamine-based COFs composite membranes via an oligomer-triggered interfacial polymerization (OT-IP) process on a hydrolyzed polyacrylonitrile (HPAN) substrate, in which the interfacial reaction occurred between an acetic acid aqueous solution and an organic solution of 1,3,5-triformylphloroglucinol (Tp) in n-hexane and tris(4-aminophenyl)amine (TAPA) in mesitylene premixed in a short time. The Tp-TAPA oligomers generated during the premixing were characterized in terms of morphology and molecular weight. The TpTAPA film formation during the OT-IP process was in situ observed through an optical contact angle measurement device. The TpTAPA/HPAN composite membranes displayed a water permeance of 68.1 L⋅m−2⋅h−1·bar−1, and the rejections of different dye (EBT, CR) and drug (DG, AG) molecules above 92.0%. In addition, the composite membrane showed excellent stability in acidic solution and continuous filtration for 75 h. The results indicated that the OT-IP approach is a feasible and efficient approach to fabricate triphenylamine-based COF composite membranes with water-insoluble monomers.