Postsynthetic Transformation of Imine- into Nitrone-Linked Covalent Organic Frameworks for Atmospheric Water Harvesting at Decreased Humidity

Herein, we reporta facile postsynthetic linkage conversionmethodgiving synthetic access to nitrone-linked covalent organic frameworks(COFs) from imine- and amine-linked COFs. The new two-dimensional(2D) nitrone-linked covalent organic frameworks, NO-PI-3-COF and NO-TTI-COF,are obtained with high crystallinity and large surface areas. Nitrone-modifiedpore channels induce condensation of water vapor at 20% lower humiditycompared to their amine- or imine-linked precursor COFs. Thus, thetopochemical transformation to nitrone linkages constitutes an attractiveapproach to postsynthetically fine-tune water adsorption propertiesin framework materials.