Sculpting Mesoscopic Helical Chirality into Covalent Organic Framework Nanotubes from Entirely Achiral Building Blocks

The diversification of chirality in covalent organic frameworks (COFs) holds immense promise for expanding their properties and functionality. Herein, we introduce an innovative approach for imparting helical chirality to COFs and fabricating a family of chiral COF nanotubes with mesoscopic helicity from entirely achiral building blocks for the first time. We present an effective 2,3-diaminopyridine-mediated supramolecular templating method, which facilitates the prefabrication of helical imine-linked polymer nanotubes using unprecedented achiral symmetric monomers. Through meticulous optimization of crystallization conditions, these helical polymer nanotubes are adeptly converted into imine-linked COF nanotubes boasting impressive surface areas, while well preserving their helical morphology and chiroptical properties. Furthermore, these helical imine-linked polymers or COFs could be subtly transformed into corresponding more stable and functional helical beta-ketoenamine-linked and hydrazone-linked COF nanotubes with transferred circular dichroism via monomer exchange. Notably, despite the involvement of covalent bonding breakage and reorganization, these exchange processes overcome thermodynamic disadvantages, allowing mesoscopic helical chirality to be perfectly preserved. This research highlights the potential of mesoscopic helicity in conferring COFs with favourable chiral properties, providing novel insights into the development of multifunctional COFs in the field of chiral materials chemistry. A series of imine-, beta-ketoenamine-, and hydrazone-linked covalent organic frameworks (COFs) with unique mesoscopic helical chirality were constructed from entirely achiral building blocks using helical amorphous imine-linked polymers as raw materials based on dynamic covalent chemistries. The crystallinity and helicity of the resulting COFs could be well balanced despite the whole process involved the covalent bonding breakage and reorganization.image

Automated summary

This study introduces an innovative method to impart helical chirality to covalent organic frameworks (COFs) and fabricate a family of chiral COF nanotubes. The helical polymer nanotubes are effectively converted into COF nanotubes with impressive surface areas while preserving their helical morphology and chiroptical properties. These COFs can be further transformed into more stable and functional COF nanotubes through monomer exchange, preserving the mesoscopic helical chirality. This research highlights the potential of mesoscopic helicity in conferring COFs with favorable chiral properties and provides novel insights into the development of multifunctional COFs in the field of chiral materials chemistry.