All sp2 carbon covalent organic frameworks

sp2 carbon covalent organic frameworks (COFs) are a unique class of crystalline 2D polymers of all sp2 carbon atoms, which can be designed via topology diagrams and synthesized by polycondensation. sp2 carbon COFs comprise conjugated but planar polymers and periodically ordered π columns across materials, offering a molecular platform for the design of semiconducting 2D polymers. The ordered 2D π-conjugated polymers provide a chemical basis to explore a diversity of properties and functions that are specific to sp2 carbon organic architectures. Covalent organic frameworks (COFs) are a class of crystalline polymers that integrate organic units into 2D and 3D skeletons to achieve ordered yet extended structures via topology-directed polymerization. Recent progress in chemistry over the past 4 years has greatly raised the ability to design the frameworks to attain fully π-conjugated all sp2 carbon structures. In this Opinion article, we summarize the chemistry to explore sp2 carbon frameworks by highlighting their design principles and synthetic strategies to show the structural scope and diversity. We scrutinize the properties and functions of sp2 carbon frameworks to elucidate their structural origins. We predict key fundamental issues for sp2 carbon frameworks and future directions from chemistry, physics, and materials perspectives. Covalent organic frameworks (COFs) are a class of crystalline polymers that integrate organic units into 2D and 3D skeletons to achieve ordered yet extended structures via topology-directed polymerization. Recent progress in chemistry over the past 4 years has greatly raised the ability to design the frameworks to attain fully π-conjugated all sp2 carbon structures. In this Opinion article, we summarize the chemistry to explore sp2 carbon frameworks by highlighting their design principles and synthetic strategies to show the structural scope and diversity. We scrutinize the properties and functions of sp2 carbon frameworks to elucidate their structural origins. We predict key fundamental issues for sp2 carbon frameworks and future directions from chemistry, physics, and materials perspectives. the degree of structural order in materials. In a compound with crystallinity, its atoms or structural units are arranged in a periodic manner. the delocalization of π electrons via the overlap of aligned sp2 hybrid orbitals of carbon atoms across the whole structure. the organic unit at the branching point of polygons in COFs. the organic unit at the edge site that links knots in COFs. chemical reactions in which the polymer is originated by successive bonds between monomers by emitting condensed molecules during the bonding process. carbon atom that adopts sp2 hybridization (the 2s orbital mixes with only two of the three available 2p orbitals) to enable sigma and π bonds. the scheme in which monomers are designed to possess specific geometries so that their connections enable the growth of extended polygonal architectures.