Editorial: Materials for Electroanalysis Based on Advanced Frameworks.

Abstract

Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) are two emerging classes of extended porous structures, which seek to develop the reticular chemistry beyond molecules and open up new horizons for compositions, structures, properties, and applications (Yaghi, 2019; Lyu et al., 2020). Like MOFs that extend inorganic metal complexes into 2D and 3D frameworks, COFs extend organic chemistry from molecules and polymers into 2D and 3D organic structures (Diercks and Yaghi, 2017). MOFs/COFs are built with the aim of extending porous frameworks through strong bonds (coordinate/covalent interactions) between molecular building blocks (metal-containing unit-organic linker/organic-organic monomer) based on topological guides. The advantages of these approaches include controllable synthesis, pre-designable structures, and manageable functionality (Geng et al., 2020). In addition to possessing high surface area and tunable pores, both MOFs and COFs display a lot of intriguing properties including layered crystalline structures through π-π stacking and high stability which is only exhibited in graphene (Fritz and Coskun, 2020) owing to the presence of strong covalent bonds. However, metal-free COFs far from meet the growing demands of numerous fields where the role of metal in the framework structure is emphasized. This includes applications such as gas adsorption and separation, heterogeneous catalysis, electronics, electrocatalysis, and electrochemical energy storage. An effective way to address these challenges is to introduce targeted metal ions into COFs frameworks to form metal-covalent organic frameworks (MCOFs) (Dong et al., 2020). Compared with metal-free COFs, MCOFs not only have superior electrocatalytic activity but also display higher intrinsic conduction due to the involvement of the metal component. Developing distinctive synthesis methods/strategies to achieve novel MOFs and COFs holds much promise toward promoting their application. For instance, flexible and free-standing pure COFs membranes were prepared by liquid-liquid interfacial polymerization at room temperature and atmospheric pressure, which solves a major problem since COFs are generally insoluble and unprocessable powders (Liu et al., 2020). A vast number of organic monomers have been reported to date with infinite possibilities of functionalization in their resulting structures. This leads to “digital reticular chemistry” based on laboratory robotics and artificial intelligence (AI), which could achieve high-throughput experiments involving synthesis and characterization. This approach is poised to make the discoveries in MOFs and COFs more significant and easily achievable (Lyu et al., 2020).