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Acid Exfoliation of Imine-linked Covalent Organic Frameworks Enables Solution Processing into Crystalline Thin Films

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  • David W Burke, Northwestern University
  • ,
  • Chao Sun
  • Ioannina Castano, Northwestern University
  • ,
  • Nathan C Flanders, Northwestern University
  • ,
  • Austin M Evans, Northwestern University
  • ,
  • Edon Vitaku, Northwestern University
  • ,
  • David C McLeod, U.S. Army Research Laboratory, Aberdeen Proving Ground
  • ,
  • Robert H Lambeth, U.S. Army Research Laboratory, Aberdeen Proving Ground
  • ,
  • Lin X Chen, Northwestern University
  • ,
  • Nathan C Gianneschi, Northwestern University
  • ,
  • William R Dichtel, Northwestern University

Covalent organic frameworks (COFs) are highly modular porous crystalline polymers that are of interest for applications such as charge-storage devices, nanofiltration membranes, and optoelectronic devices. COFs are typically synthesized as microcrystalline powders, which limits their performance in these applications, and their limited solubility precludes large-scale processing into more useful morphologies and devices. We report a general, scalable method to exfoliate two-dimensional imine-linked COF powders by temporarily protonating their linkages. The resulting suspensions were cast into continuous crystalline COF films up to 10 cm in diameter, with thicknesses ranging from 50 nm to 20 μm depending on the suspension composition, concentration, and casting protocol. Furthermore, we demonstrate that the film fabrication process proceeds through a partial depolymerization/repolymerization mechanism, providing mechanically robust films that can be easily separated from their substrates.

Original languageEnglish
JournalAngewandte Chemie International Edition
Pages (from-to)5165-5171
Number of pages7
Publication statusPublished - 23 Mar 2020

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© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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