Humidity Sensing through Reversible Isomerization of a Covalent Organic Framework

Samik Jhulki, Austin M. Evans, Xue Li Hao, Matthew W. Cooper, Cameron H. Feriante, Johannes Leisen, Hong Li, David Lam, Mark C. Hersam, Stephen Barlow, Jean Luc Brédas, William R. Dichtel, Seth R. Marder

Research output: Contribution to journalArticle

Abstract

Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted 1,4-dihydroxybenzene (diiminol) moieties, undergoes color changes in the presence of solvents or solvent vapor that are rapid, passive, reversible, and easily detectable by the naked eye. A new visible absorption band appears in the presence of polar solvents, especially water, suggesting reversible conversion to another species. This reversibility is attributed to the ability of the diiminol to rapidly tautomerize to an iminol/cis-ketoenamine and its inability to doubly tautomerize to a diketoenamine. Density functional theory (DFT) calculations suggest similar energies for the two tautomers in the presence of water, but the diiminol is much more stable in its absence. Time-dependent DFT calculations confirm that the iminol/cis-ketoenamine absorbs at longer wavelength than the diiminol and indicate that this absorption has significant charge-transfer character. A colorimetric humidity sensing device constructed from an oriented thin film of the COF responded quickly to water vapor and was stable for months. These results suggest that tautomerization-induced electronic structure changes can be exploited in COF platforms to give rapid, reversible sensing in systems that exhibit long-term stability.

Original languageEnglish
Pages (from-to)783-791
Number of pages9
JournalJournal of the American Chemical Society
Volume142
Issue number2
DOIs
Publication statusPublished - Jan 15 2020

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Jhulki, S., Evans, A. M., Hao, X. L., Cooper, M. W., Feriante, C. H., Leisen, J., Li, H., Lam, D., Hersam, M. C., Barlow, S., Brédas, J. L., Dichtel, W. R., & Marder, S. R. (2020). Humidity Sensing through Reversible Isomerization of a Covalent Organic Framework. Journal of the American Chemical Society, 142(2), 783-791. https://doi.org/10.1021/jacs.9b08628