Title: Solvothermal depolymerization and recrystallization of imine-linked two-dimensional covalent organic frameworks

Abstract

Mechanistic understanding into the formation and growth of imine-linked two-dimensional (2D) covalent organic frameworks (COFs) is needed to improve their materials quality and access larger crystallite sizes, both of which limit the promise of 2D COFs and 2D polymerization techniques. Here we report a previously unknown temperature-dependent depolymerization of colloidal 2D imine-linked COFs, which offers a new means to improve their crystallinity. 2D COF colloids form at room temperature but then depolymerize when their reaction mixtures are heated to 90 °C. As the solutions are cooled back to room temperature, the 2D COFs repolymerize and crystallize with improved crystallinity and porosity, as characterized by X-ray diffraction, infrared spectroscopy and N₂ porosimetry. The evolution of COF crystallinity during the solvothermal depolymerization and repolymerization processes was characterized by in situ wide angle X-ray scattering, and the concentrations of free COF monomers as a function of temperature were quantified by variable temperature 1H NMR spectroscopy. The ability of a 2D COF to depolymerize under these conditions depends on both the identity of the COF and its initial materials quality. For one network formed at room temperature (TAPB-PDA COF), a first depolymerization process is nearly complete, and the repolymerization yields materials with dramatically enhancedmore » crystallinity and surface area. Already recrystallized materials partially depolymerize upon heating their reaction mixtures a second time. A related 2D COF (TAPB-DMTA COF) forms initially with improved crystallinity compared to TAPB-PDA COF and then partially depolymerizes upon heating. These results suggest that both high materials quality and network-dependent properties, such as interlayer interaction strength, influence the extent to which 2D COFs resist depolymerization. These findings offer a new means to recrystallize or solvent anneal 2D COFs and may ultimately inform crystallization conditions for obtaining large-area imine-linked two-dimensional polymers from solution.« less

Authors:

Ji, Woojung  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5329-0628"

Hamachi, Leslie S.  ^[2];

• Search DOE PAGES for author "Hamachi, Leslie S."
• Search DOE PAGES for ORCID "0000-0001-6299-8695"

Natraj, Anusree  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-4171-9815"

Flanders, Nathan C.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-2096-4803"

Li, Rebecca L.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-7208-3413"

Chen, Lin X.  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-8450-6687"

Dichtel, William R.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-3635-6119"

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+ Show Author Affiliations

1. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
2. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA, Department of Chemistry and Biochemistry, California Polytechnic State University, San Luis Obispo, California, 93407, USA
3. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA, Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA

Publication Date:

Wed Dec 15 00:00:00 EST 2021

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; U.S. Army Research Laboratory, U.S. Army Research Office (ARO); National Science Foundation (NSF)

OSTI Identifier:

1833455

Alternate Identifier(s):

OSTI ID: 1868931

Grant/Contract Number:  

AC02-06CH11357; DMR-1720139; ECCS1542205

Resource Type:

Published Article

Journal Name:

Chemical Science

Additional Journal Information:

Journal Name: Chemical Science Journal Volume: 12 Journal Issue: 48; Journal ID: ISSN 2041-6520

Publisher:

Royal Society of Chemistry (RSC)

Country of Publication:

United Kingdom

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY