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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, 22:07 and posted on 22.09.2020, 11:20 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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