Crystalline and Stable Benzofuran-Linked Covalent Organic Frameworks from Irreversible Cascade Reactions

We report the synthesis
of crystalline two-dimensional covalent
organic frameworks (COFs) by connecting hydroxybenzene-aldehyde and
acetonitrile building blocks to form cyano-substituted benzofuran
linkages. Unlike the majority of COFs that were synthesized based
on condensation reactions, the COFs in this report are crystallized
from irreversible cascade reactions involving consecutive cyanide
migration, ring-closure, and oxidation reactions. The irreversible
property endows the COFs with high chemical stability in both acid
and base and allows them to be postsynthetically modified to install
predesigned functionality under harsh conditions. We highlight that
the functionalized COFs serve as exceptional vehicles for superprotonic
conductions.