(576f) Process Optimization for Controlling the Morphology of Cof-5 Crystals

Covalent Organic Frameworks (COFs) have gained significant attention in the field of material science over last two decades. 2D boronate-ester linked frameworks like COF-5, are porous, crystalline, organic polymers with low density, that can be used for numerous applications such as gas storage and as membranes for various industrial purification applications. COF-5 exhibits high thermal stability, high surface area and permanent porosity widening the scope of its applicability. To maximize its applicability, it is essential to optimize and control the morphology of the crystallites by tweaking appropriate processing conditions. COF-5 can be synthesized by evaporative crystallization using 1,4-diboronic acid (PBBA) and Hexahydroxy Triphenylene (HHTP), in an equimolar solvent mixture of Dioxane and Mesitylene. This process is heterogenous, uncatalyzed and slow, needing three days to reach a considerable and acceptable yield. Researchers have previously made efforts to reduce the reaction barrier and reaction time to 20 hrs. However, a systematic understanding of the effects of alterations in processing conditions on crystallite yield and morphology remain unanswered. Effective and accelerated crystallization of COF-5 while controlling the structure of these crystals is the prime focus of our research. This study has addressed the optimization of processing conditions, catalyst content, and solvent environment to synthesize and control the morphology of COF-5 at a higher rate. Additionally, these conditions were utilized to grow COF-5 films on substrates, while ensuring that their crystallite properties remained intact. Experimentally derived kinetic models using the optimized conditions, have been coupled with population balance equations to get a deeper insight on the crystal growth mechanisms of COF-5.