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.

Emerging porous organic polymers for biomedical applications

“…Many systematic reviews have been published on the design and synthetic strategies for different types of POPs. 41,42,48,54,77,175,190–192 Finding suitable synthetic conditions to generate different forms of POPs is of great importance for targeted biomedical applications. In the early stage, most POPs were prepared as insoluble powders or polycrystalline aggregates, which were difficult to process to other forms and challenging for many applications.…”

Norbornane-based covalent organic frameworks for gas separation

“…Unlike polymers, COFs are well known for their crystalline and porous structures, which are generated through a covalent-bond-linked assembly of organic linkers arranged in an ordered form. 6–8 Owing to their ordered pore structure, uniform porosity, high crystallinity, high accessible surface area, and tunable pore chemistry, COFs have diverse applications, including in optoelectronics, separation, energy storage, sensing, catalysis, and biomedicine. 9 Conventionally, COFs are synthesized from commercially available symmetric planar organic precursor materials.…”

Crystallizing Sub 10 nm Covalent Organic Framework Thin Films via Interfacial–Residual Concomitance

“…This process leads to COF crystallization at the solid–liquid interface to form one-dimensional (1D) COF fibers. The COF fibers further endure supramolecular interaction to generate 2D COF thin films . A parallel interfacial crystallization of TpAzo and TpDPP COF thin films occurs in the liquid–liquid interface.…”

“…In the second method (S–F), 100 mL of the as-synthesized COF nanosphere solution , (containing 3.5 mg of COF nanospheres) in dichloromethane is employed (Figures S1, S5, S6, S11, S17, and S20). The liquid–liquid interfacial crystallization is integrated with the residual crystallization by dropwise addition of 100 mL of deionized water on top of the COF nanosphere solution in dichloromethane.…”