Post-synthetic Transformation of Imine- into Nitrone-linked Covalent Organic Frameworks for Atmospheric Water Harvesting at Decreased Humidity

Herein, we report a facile post-synthetic linkage conversion method giving synthetic access to nitrone-linked covalent organic frameworks from imine- and amine-linked COFs. The new, 2D nitrone-linked covalent organic frameworks, NO-PI-3-COF and NO-TTI-COF are obtained with high crystallinity and large surface areas. Nitrone-modified pore channels induce capillary condensation of water vapor at 20% lower humidity compared to their amine- or imine-linked precursor COFs. Thus, the topochemical transformation to nitrone linkages constitutes an attractive approach to post-synthetically fine-tune water adsorption properties in framework materials.