Steric effect of intermediates induces formation of three-dimensional covalent organic frameworks

Constructing three-dimensional covalent organic frameworks (3D COFs) remains a significant challenge compared to other areas of reticular chemistry. Most existing methods for constructing 3D COFs emphasize the necessity of at least one precursor being extended into 3D space. As a result, designing and synthesizing precursors with specific stereoconformations has become a dominant strategy for discovering new 3D COFs. In this study, we leverage the principle that the steric hindrance of intermediates during COF formation is inherently greater than that of the precursors. We demonstrate a strategy utilizing multinode porphyrin blocks with eight rotatable knots to create intermediates with steric hindrance-confined rigid stereoconformations, which can be viewed as active precursors for guiding 3D formation of COFs with high crystallinity. This approach paves an avenue to self-adaptive COF growth towards diverse 3D topologies that may circumvent obstacles for traditional precursor synthesis.