Structural design and determination of 3D covalent organic frameworks

The challenging synthesis of 3D covalent organic frameworks (COFs) strongly restrains their structural diversity, which is highly important to develop the chemistry of 3D COFs. Substantial development of the structural diversity of 3D COFs has been achieved through topology evolution, building block expansion, linkage development, and post-synthetic functionalization. The structural elucidation of 3D COFs is an important but complex task during the extension of their structural diversity to build accurate structure–property relationships. On growing large-sized single-crystal and high-quality microcrystalline powders, single-crystal X-ray diffraction and 3D electron diffraction techniques have been successfully applied to determine 3D COFs with atomic resolution. Considering the uncertainties in structural modeling and challenges in powder X-ray diffraction techniques, single-crystal X-ray diffraction and electron diffraction techniques are suggested techniques to determine the structure of 3D COFs. 3D covalent organic frameworks (COFs) represent a unique class of crystalline porous materials that allow the precise integration of organic molecular building blocks into 3D networks through the formation of covalent bonds. Considering their numerous open sites and hierarchical pore structures, 3D COFs have shown interesting potential in many areas, especially gas adsorption and catalysis. However, the chemistry of 3D COFs has been restrained largely due to their limited structural diversity and complicated structural determination. In this review, we summarize the key strategies and techniques used to diversify and determine the structure of 3D COFs. Finally, the remaining challenges and prospects concerning the structural design and determination of 3D COFs are presented. 3D covalent organic frameworks (COFs) represent a unique class of crystalline porous materials that allow the precise integration of organic molecular building blocks into 3D networks through the formation of covalent bonds. Considering their numerous open sites and hierarchical pore structures, 3D COFs have shown interesting potential in many areas, especially gas adsorption and catalysis. However, the chemistry of 3D COFs has been restrained largely due to their limited structural diversity and complicated structural determination. In this review, we summarize the key strategies and techniques used to diversify and determine the structure of 3D COFs. Finally, the remaining challenges and prospects concerning the structural design and determination of 3D COFs are presented. the state or extent of the building block that is connected or interconnected. the experimental science that deals with the arrangement of atoms in the structures of crystals. the sizes, shapes, positions angles, and dimensions of the building blocks. an analytical technique similar to SCXRD. It uses the diffraction of electron beams to determine the structure of a submicrometer crystal. a language used to describe COFs based on their connectivity. It is described by a set of vertices and the edges that link them. These topologies are named as a three-letter lowercase, bolded symbol, which represents a prototypical solid-state structure with this topology or an arbitrary designation. defined as the linking of molecular building units by strong bonds into crystalline extended structures. an analytical technique that uses the diffraction of incident X-rays to determine the structure of a crystal with atomic precision. the effects describing nonbonding interactions that influence the shape (conformation) and reactivity of ions and molecules.