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Amine-linked Covalent Organic Frameworks as a Powerful Platform for Post-Synthetic Modification: Structure Interconversion and Combined Linkage- and Pore-Wall-Modification

preprint
submitted on 21.09.2020 and posted on 22.09.2020 by Lars Grunenberg, Gökcen Savasci, Maxwell Terban, Viola Duppel, Igor Moudrakovski, Martin Etter, Robert E. Dinnebier, Christian Ochsenfeld, Bettina Lotsch
Covalent organic frameworks have emerged as a powerful synthetic platform for installing and interconverting dedicated molecular functions on a crystalline polymeric backbone with atomic precision. Here, we present a novel strategy to directly access amine-linked covalent organic frameworks, which serve as a scaffold enabling pore-wall modification and linkage-interconversion by new synthetic methods based on Leuckart-Wallach reduction with formic acid and ammonium formate. Frameworks connected entirely by secondary amine linkages, mixed amine/imine bonds, and partially formylated amine linkages are obtained in a single step from imine-linked frameworks, or directly from corresponding linkers in a one-pot crystallisation-reduction approach. The new, 2D amine-linked covalent organic frameworks, rPI-3-COF, rTTI-COF, and rPy1P-COF, are obtained with high crystallinity and large surface areas. Secondary amines, installed as reactive-sites on the pore wall, enable further post-synthetic functionalisation to access tailored covalent organic frameworks, with increased hydrolytic stability, as potential heterogeneous catalysts.

Funding

Fuel from sunlight: Covalent organic frameworks as integrated platforms for photocatalytic water splitting and CO2 reduction

European Research Council

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SFB 1333:  Molecular Heterogeneous Catalysis in Confined Geometries

Deutsche Forschungsgemeinschaft

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EXC 2089:  e-conversion

Deutsche Forschungsgemeinschaft

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Max Planck Society

Center for Nanoscience (CeNS)

History

Email Address of Submitting Author

l.grunenberg@fkf.mpg.de

Institution

Max Planck Institute for Solid State Research

Country

Germany

ORCID For Submitting Author

0000-0002-6831-4626

Declaration of Conflict of Interest

The authors declare no competing interests.

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