Covalent organic frameworks (COFs) are organic porous materials with many potential applications, which very often depend on the presence of chemical functionality at the organic building blocks. Functionality that cannot be introduced into COFs directly via de novo syntheses can be accessed through post-synthetic modification (PSM) strategies. Current strategies for the post-synthetic modification of COFs involve (i) incorporation of a variety of active metal species by using metal complexation through coordination chemistry, (ii) covalent bond formation between existing pendant groups and incoming constituents and (iii) chemical conversion of linkages. (iv) The post-synthetic modification is sometimes assisted by a monomer truncation strategy for the internal functionalization of COFs. (v) Even more intriguing methods that go beyond PSM are herein termed building block exchange (BBE) which encompasses framework-to-framework transformations taking advantage of the fact that reversible bond formation is a characteristic feature of COFs. This strategy allows the use of protoCOF structures (i.e., the utilization of a parent COF as a template) for the evolution of new COF structures with completely new components.

Dipyrazino[2,3-f:2′,3′-h]quinoxaline also known as 1,4,5,8,9,12-hexaazatriphenylene (HAT) is an electron deficient, rigid, planar, aromatic discotic system with an excellent π–π stacking ability. Because it is one of the smallest two-dimensional N-containing polyheterocyclic aromatic systems, it has been used as the basic scaffold for larger 2D N-substituted polyheterocyclic aromatics. Furthermore, it is the building block of choice in a plethora of molecular, macromolecular and supramolecular systems for a variety of applications. This review is aimed to critically review the research performed during the almost three decades of research based on HAT from the synthetic, theoretical and application points of view. The design principles and synthetic strategies towards HAT derivatives will be established and their use in n-type semiconductors, sensors, nonlinear optical chromophores, liquid crystals, microporous polymers for energy storage and nano and microstructures will reveal the relevance of HAT as a basic scaffold in the areas of organic materials and nanoscience.

A novel naphthalene diimide-based covalent organic framework (NDI-COF) has been synthesized and successfully exfoliated into COF nanosheets (CONs) to provide an efficient electrocatalyst for the oxygen reduction reaction.

In this study, we present a novel approach for the synthesis of covalent organic frameworks (COFs) that overcomes the common limitations of non‐scalable solvothermal procedures. Our method allows for the room‐temperature and scalable synthesis of a highly fluorinated DFTAPB‐TFTA‐COF, which exhibits intrinsic hydrophobicity. We used DFT‐based calculations to elucidate the role of the fluorine atoms in enhancing the crystallinity of the material through corrugation effects, resulting in maximized interlayer interactions, as disclosed both from PXRD structural resolution and theoretical simulations. We further investigated the electrocatalytic properties of this material towards the oxygen reduction reaction (ORR). Our results show that the fluorinated COF produces hydrogen peroxide selectively with low overpotential (0.062 V) and high turnover frequency (0.0757 s⁻¹) without the addition of any conductive additives. These values are among the best reported for non‐pyrolyzed and metal‐free electrocatalysts. Finally, we employed DFT‐based calculations to analyse the reaction mechanism, highlighting the crucial role of the fluorine atom in the active site assembly. Our findings shed light on the potential of fluorinated COFs as promising electrocatalysts for the ORR, as well as their potential applications in other fields.