Homogeneous Polymerization of Self-standing Covalent Organic Framework Films with High Performance in Molecular Separation

• Published in: ACS applied materials & interfaces 2020-09, Vol.12 (37), p.41942-41949
• Main Authors: He, Yasan, Lin, Xiaogeng, Chen, Jianhua, Guo, Zhiyong, Zhan, Hongbing
• Format: Article
• Language: English
• Subjects: Functional Nanostructured Materials (including low-D carbon)
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.0c11022

Covalent organic frameworks (COFs) are typically isolated as microcrystalline powders. It remains fundamentally challenging to fabricate COFs into high-quality self-standing films to take full advantage of their ordered pore channels for molecular separation. Here, we report a new strategy for fabricating self-standing imine-linked COF films via homogeneous polymerization where films emerge from clear solutions without forming amorphous precipitates. The abundant basic nitrogen atoms of the monomers acted as a reaction controller to realize the homogeneous polymerization and also promoted the tight self-aggregation of COF crystallites to form compact films via H-bonding. The chemically supported self-standing COF films on nylon membranes were also developed via an in situ growth method. The resulting films showed an unprecedentedly ultrafast permeance of 2822 L m–2 h–1 MPa–1 with a high rejection rate (99.8%) in the filtration of a congo red (CR) solution, demonstrating the advantage of this new strategy in fabricating high-quality self-standing COF films.