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In Situ Monitoring of Mechanochemical Covalent Organic Framework Formation Reveals Templating Effect of Liquid Additive

preprint
submitted on 22.09.2020 and posted on 23.09.2020 by Sebastian Emmerling, Luzia S. Germann, Patrick Julien, Igor Moudrakovski, Martin Etter, Tomislav Friscic, Robert E. Dinnebier, Bettina Lotsch
Covalent organic frameworks (COFs) have emerged as a new class of molecularly precise, porous functional materials characterized by a broad structural and chemical versatility, leading to a diverse range of applications. Despite the increasing popularity of COFs, fundamental aspects of their formation are poorly understood and profound experimental insights into their formation processes are still lacking. Here we use a combination of in situ X-ray powder diffraction and Raman spectroscopy to elucidate the reaction mechanism of mechanochemically synthesized imine COFs, leading to the observation of key reaction intermediates. Real-time monitoring provides experimental evidence of templating effects by the liquid additive for the subsequent pore formation and layer assembly. Moreover, the solid-state catalyst scandium triflate Sc(OTf)3 is revealed to be instrumental in directing the reaction kinetics and mechanism, resulting in products with crystallinity and porosity en par with solvothermally synthesized COFs. This work highlights the potential of mechanochemistry as a green synthetic route towards COF synthesis, and emphasizes the subtle interplay between choice of liquid additives, catalysts, and activation procedure.

Funding

Deutsche Forschungsgemeinschaft 358283783, SFB 1333

ERC Starting grant 639233

Cluster of Excellence e-conversion (EXC 2089)

Swiss National Science Foundation P2SKP2_187638

Center for Nanoscience

NSERC Discovery Grant (RGPIN-2017-06467)

NSERC Discovery Accelerator award (RGPAS 507837-17)

History

Email Address of Submitting Author

luzia.germann@gmail.com

Institution

McGill University

Country

Canada

ORCID For Submitting Author

0000-0003-1760-5842

Declaration of Conflict of Interest

no conflict of interest

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