Mohamad Hmadeh
American University of Beirut, Lebanon
Title: Synthesis and structural evolution of MOFs and ZIFs via a reaction diffusion process at room temperature
Biography
Biography: Mohamad Hmadeh
Abstract
MOF-199, ZIF-8 and ZIF67 crystals were successfully prepared through the diffusion of the outer electrolytes (metal cations or organic linkers) into an agar gel matrix, in which the inner electrolytes were immobilized. As the electrolytes diffuse into the gel, crystals were shown to precipitate. This novel method for synthesizing MOFs and ZIFs is rapid, scalable, and environmentally friendly. Due to the reactants being initially separated and poured on the top of each other, a supersaturation gradient was established starting at the gel-solution interface and extending down the reaction tube. Nucleation, growth, and ripening of the crystalline solid is highly dependent on supersaturation, such that nucleation dominates near the interface resulting in smaller crystals whereas further down the reaction tube, growth dominates leading to larger crystals. Accordingly, the supersaturation gradient produced various crystal sizes at different heights along the reaction tube. Furthermore, by varying the temperature, the concentrations of the reagents, and the thickness of the gel matrix, control of the size and morphology of the crystals was achieved and several key parameters in the mechanism of crystal growth are discussed.