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

The diversification of chirality in covalent organic frameworks (COFs) holds immense promise for expandingtheir 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 thefirst time. We present an effective 2,3-diaminopyridine-mediated supramolecular templating method, which facilitatesthe prefabrication of helical imine-linked polymer nanotubes using unprecedented achiral symmetric monomers.Through meticulous optimization of crystallization conditions, these helical polymer nanotubes are adeptly convertedinto imine-linked COF nanotubes boasting impressive surface areas, while well preserving their helical morphology andchiroptical properties. Furthermore, these helical imine-linked polymers or COFs could be subtly transformed intocorresponding more stable and functional helical β-ketoenamine-linked and hydrazone-linked COF nanotubes withtransferred circular dichroism via monomer exchange. Notably, despite the involvement of covalent bonding breakageand reorganization, these exchange processes overcome thermodynamic disadvantages, allowing mesoscopic helicalchirality to be perfectly preserved. This research highlights the potential of mesoscopic helicity in conferring COFs withfavourable chiral properties, providing novel insights into the development of multifunctional COFs in the field of chiralmaterials chemistry.

Xinlin Zha, Guilin Xu, Niaz Ali Khan, Zhong Yan, Mengjuan Zuo, Yi Xiong, Ying Liu, Haining You, Yi Wu, Ke Liu, Mufang Li, and Dong Wang, Sculpting Mesoscopic Helical Chirality into Covalent Organic Framework Nanotubes from Entirely Achiral Building Blocks, Angew. Chem. Int. Ed. 2023, e202316385