Covalent Organic Frameworks and Supramolecular Nano-Synthesis

Abstract

Covalent organic frameworks (COFs) prevail as diverse forms of solids in bulk, e.g., powders, monoliths, thin films, etc. These architectures constructed from a similar net design at the molecular to framework level differ in their hierarchical assembly laid upon the nano- to mesoscale structures. However, even after a decade and a half of research, the primary focus of the field lies on the covalent reticular structure, and the chemistry of COFs in the nano regime is often overlooked. The COF nanostructures (nanosheets, nanofibers, and nanospheres) are quite distinct from the bulk forms and often influence the properties of their bulk counterparts. Although the reticular chemistry of strong directional covalent bonds generates these nanostructures from molecular building blocks, divergent chemical and supramolecular interactions assemble these nanomotifs into the macroscale solids. We believe that the synthetic design can be extended beyond the molecule → framework to the nano → meso → macroscale hierarchy in COFs. In this review, we take a closer look at this “supramolecular nanosynthesis” and discuss how the properties of the nanostructures reciprocate in the bulk forms.