Covalent Organic Frameworks: Organic Chemistry Extended into Two and Three Dimensions

Covalent organic framework (COF) synthesis has achieved a new level of design through topological, geometric, and chemical control. 2D and 3D COF crystallinity no longer relies entirely on reversible linkage dynamics due to extensive development in the control of stacking interactions, highly directional bonding motifs, in situ tautomerization and cyclization strategies, and postsynthetic linkage modifications. The precision of molecular organic chemistry and the power of single-crystal X-ray diffraction of molecules are extended to 2D and 3D COFs, thereby expanding the scope of organic chemistry and its advantages beyond discrete molecules. The fact that COFs can be made as architecturally and chemically stable structures allows for chemical reactions to be carried out within their pores, creating structures that are molecularly precise in their functionality and metrics. Covalent organic frameworks are constructed by covalently linking organic molecules into crystalline 2D and 3D networks. Their architectural and chemical stability, coupled with their porosity, has allowed them to be used as starting materials and products of molecular organic reactions. Increasingly sophisticated structural and chemical design strategies have enabled the synthesis of complex 3D, 2D, and 1D (weaving) structures from geometrically predefined building blocks. Like small molecules, these materials allow for precise spatial organization of chemical functionalities but do so at length scales ranging from a few angstroms to several microns. Covalent organic frameworks are constructed by covalently linking organic molecules into crystalline 2D and 3D networks. Their architectural and chemical stability, coupled with their porosity, has allowed them to be used as starting materials and products of molecular organic reactions. Increasingly sophisticated structural and chemical design strategies have enabled the synthesis of complex 3D, 2D, and 1D (weaving) structures from geometrically predefined building blocks. Like small molecules, these materials allow for precise spatial organization of chemical functionalities but do so at length scales ranging from a few angstroms to several microns. a chemical coupling involving the generation of water as a byproduct. the regular ordering of atoms in a solid with translational symmetry. the length scale on which a material exhibits translational symmetry. a process by which linkages that do not contribute to the thermodynamically preferred crystalline phase of a COF are either exchanged or broken and remade to obtain the appropriate connectivity. a unit of a COF that links two vertices. an analytical technique conceptually similar to SXRD, but using an electron beam and capable of analysis of submicron crystallites too small for analysis with SXRD. to link geometrically well-defined building units into an ordered 2D or 3D network. an analytical technique that uses the diffraction of incident X-rays to determine the structure of a crystal with atomic precision. a reaction taking place in a closed system, in which the solvents are heated above their atmospheric pressure boiling points. This is often useful in COF synthesis, as byproducts of condensation reactions are kept in the system, maintaining the reversibility of the linkage. a chemical reaction interconverting two constitutional isomers. a unit of a COF that contains at least three points of extension. This is usually an individual linker, but can also be a linkage moiety for linkages that involve cyclotrimerization.