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.

An imine-linked covalent organic framework ([HCC]_0.5-TPB-DMTP-COF), endowed with reactive ethynyl groups on the walls of one-dimensional pores, has been used as a platform for pore-wall surface engineering with triazole and thiol groups to yield TPB-DMTP-COF-SH, which is suitable to interact very efficiently with mercury ions. The evaluation of the carefully designed TPB-DMTP-COF-SH is addressed as an effective and selective system for mercury sorption. The obtained results reveal an extraordinary capacity and a great efficiency of the polymeric material with a very high distribution coefficient value K_d = 3.23 × 10⁹. Thus, the level of mercury of a highly concentrated aqueous solution, 10 mg L⁻¹ of Hg(II), is dramatically decreased, below the limits of what is considered to be drinking water, upon treatment with TPB-DMTP-COF-SH for a few minutes. The TPB-DMTP-COF-SH retention value of Hg(II) from water is 99.98% within 2 minutes and its record uptake capacity is 4395 mg g⁻¹ which represents the highest value reported so far. Besides TPB-DMTP-COF-SH captures other extremely toxic heavy metal ions such as Sn(II) and Pb(II) being quite selective versus Cd(II) or As(III). These results suggest that TPB-DMTP-COF-SH constitutes a realistic alternative for the remediation of contaminated spaces from an environmental perspective.

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.

Covalent organic frameworks (COFs) possess intrinsic nanoscale pores, limiting mass transport and impacting their utility in many applications, such as catalysis, supercapacitors, and gas storage, demanding efficient diffusion throughout the material. Hierarchical porous structures, integrating larger macropores with inherent micro‐/meso‐pores, facilitate rapid mass transport. Recently, the fabrication of aerogel monoliths is reported exclusively from imine‐linked COFs, offering flexibility in aerogel composition. However, challenges in synthesizing robust β‐ketoenamine‐based COFs with comparable surface areas prompted innovative synthetic approaches. Leveraging the dynamic nature of COF bonds, in this work efficient monomer exchange from imine to partially β‐ketoenamine‐linked COFs within the gel phase is demonstrated. These aerogels can be transformed into electrodes using the compression technique. The new flexible electrodes‐based β‐ketoenamine‐linked COF composites with C super P exhibit superior durability and redox activity. Through supercapacitor assembly, the β‐ketoenamine‐linked COF electrodes outperform their imine‐based counterparts, showcasing enhanced capacitance (88 mF cm⁻²) and stability at high current densities (2.0 mA cm⁻²). These findings underscore the promise of β‐ketoenamine‐linked COFs for pseudocapacitor energy storage applications.

A new imine-based covalent organic framework (COF) functionalized in its cavities with moieties of the chromophore Nile Red has been synthesized and characterized. Using mechanical (ultrasonics) and chemical (acid-self-exfoliation) methods, exfoliation of the COF powder has been explored in water and water/organic media. In the latter, the obtained colloids exhibit dual emission originating from the Nile Red units (red) and the COF framework (green) that can be employed to prepare ratiometric sensors of polarity and acidity. Thus, taking advantage of the in situ exfoliation of the material in methacrylic monomers, free-standing polymeric films that preserve the optical properties of the exfoliated COF have been prepared. Finally, 3D liquid crystal display (LCD) additive manufacturing has been employed to prepare the dual emissive composites as tailored 3D-printed objects.