Synthesis and characterization of covalent organic frameworks (COFs) with interlayer hydrogen bonding

Covalent organic frameworks (COFs) are crystalline, porous polymers which are made up of light elements (C, H, O, N) with organic monomers that are linked together via covalent bonds. These polymers grow either 2D or 3D fashion. In 2D-COFs, the sheets can be held together by noncovalent forces including van der Waals, aromatic stacking, and hydrogen bonding interactions. Non-covalent interactions play a critical role in the formation of 2D-COFs as well as influencing the bulk properties of the resultant materials such as electrical conductivity, pore size control, and even their hydrolytic stability. In this research, we selected a tritopic aldehyde linker having three amide hexyl groups as the H-bonding monomer. Different imine COFs were synthesized using difunctionalized amine linkers. COFs were synthesized using solvothermal conditions and activated with super critical carbon dioxide (scCO₂). Synthesized COFs were characterized with FT-IR spectroscopy, powder X-ray diffraction (PXRD), and computer modeling. Surface area of COFs was determined using N₂ adsorption−desorption experiments. In this study we observed variation in crystallinity and surface area of synthesized COFs with change in the interlayer interactions. This study expands the scope of COF chemistry with interlayer H-bonding towards different applications.