Enhanced covalent organic frameworks processability: Synthesis of COF-polymer hybrid materials with plastic behavior

Covalent Organic Frameworks (COFs) are usually obtained as non-soluble powders that lack plasticity, making it difficult to form them into complex shapes or layouts. This inherent lack of processability limits their applicability despite their intriguing display of properties. The combination of COFs with polymeric materials represents a promising approach to make them more processable. In this work, hybrid COF-polymer materials have been prepared both through melt-blending and in situ reactions, combining imine-based COFs with polylactic acid (PLA), resulting in hybrid materials with good plastic behavior. In situ reactions enable covalent bonding of the polymeric chains to the COF backbone, promoting favorable interactions between the two phases, but tolerating only relatively low COFs loadings. On the other hand, in melt-blended hybrids, the polymeric matrix tolerates even relatively high COFs loadings (up to 5% w/w), but the properties of the final materials are less influenced by the COF concentration with respect to the in situ samples. The comparison of melt-blended and in situ COF-PLA hybrids shows the potential of the two approaches towards fully processable materials and highlights the different interactions between the COFs and the polymeric chains. 3D printing tests have been successfully carried out on the materials, to confirm the processing capabilities.