Effect of solvent and acid on the morphology of the β-ketoenamine-linked covalent organic frameworks (COFs)

Covalent organic frameworks (COFs) have proclaimed as an advanced class of porous materials with large surface area, high thermal and chemical stability, tunable molecular functionalities and porosity (micro- or mesoporosity) etc. Owing to their peculiar advantages, COFs are the materials of attraction for many researchers in several fields. The synthetic methods influence the certain properties that may result into a significant effect on the applications of these materials. The present study reports the synthesis of β-ketoenamine linked phenylene diamine based COF via solvothermal method and the effect of solvent and acid on the morphology and porosity of the synthesized COF. Reactions of phenylene diamine with 2,4,6-triformylphloroglucinol in mesitylene/dioxane solvent mixture under moderate acidic conditions at 120 °C for three days provided the crystalline powder. However, replacement of solvent with DMSO and high acidic conditions resulted into the formation of xerogels under same temperature and time conditions. The xerogel gave foam like material upon freeze drying. FE-SEM, HR-TEM, PXRD analysis revealed the difference in morphology and porosity of the COFs prepared by two methods. The synthesized COFs were studied for the dye adsorption applications and a significant difference in the efficiency was observed indicating their different morphology and porosity.