“Covalent Organic Frameworks-POlymers” COlloids: from macromolecular design to responsive self-assemblies – COPOCO

"Covalent organic frameworks" (COFs) are an emerging class of crystalline organic materials, showing tunable porosity, with a periodic structure over several dimensions. They are based on the formation of dynamic bonds, formed by condensation reactions between their molecular precursors using modular chemistry concepts. No other multi-dimensional polymerization strategy allows for today to predict and adjust the structure of the network to such a level. Although their recent development, almost 650 different chemical structures are now reported, attracting increasing interest from different fields (storage, molecular separation, catalysis, sensing, optoelectronics, encapsulation and delivery of bioactive molecules). However, COFs suffer from significant limitations: they are by nature crosslinked materials, insoluble or even sparingly dispersible in solution and often produced as polycrystalline powders or films. Despite much effort having been devoted towards the design of the physical and/or chemical properties of these materials by selecting their initial building blocks, the importance of processability for their applications has only recently emerged. The COPOCO project proposes an original “win-win” combination of responsive polymers and COFs. It aims at producing well defined COF nanoparticles (NPs) with macromolecular chains covalently attached on their surface. The polymer chains will have several roles: 1) acting as a modulator to chemically control the nucleation and growth of COFs, 2) ensuring colloidal stability of the COF NPs, 3) bringing stimuli-sensitive properties to drive on demand self-assembly between the COFs. Colloidal assembly, dealing with interactions between particles of a few nanometers to a few micrometers, provides an interesting strategy to organize the matter from the molecular level, up to the macroscopic level. Crystalline COF NPs offer a means of organizing the orientation of the polymer chains and will be used as building blocks to form nanostructured materials. Since self-assembling processes of colloidal particles are dependent upon particle size, dispersity, and shape, the organization of the resulting structures should positively correlate with COF NPs uniformity. Such an approach could pave new ways for designing macroscopic materials with oriented and tunable porosity over long distances with sensing and capture properties.