(601g) A Generalized Approach for Rapid Aqueous MOF Synthesis By Controlling Solution pH

Metal organic frameworks (MOFs) are a promising class of crystalline materials with potential to significantly advance the fields of catalysis, separations, biotechnology, and sensing, amongst others. Comprised of metal ion nodes and organic linkers, lab-based syntheses have excelled at producing novel MOFs with tuned pore size and chemical activity. However, developing a crystallization technique that meets high throughput scaling requirements and is environmentally benign remains a challenge. Currently, applying classical crystallization techniques to MOF formation are limited due to the multi-component nature. In this work, we approach understanding MOF formation through a reaction-based perspective to better understand the non-classical crystallization pathway. We demonstrate that tuning the reactant speciation, namely labile metal ion nodes and deprotonated organic acid linkers, via pH has a significant effect on MOF yield. Using this approach, we develop a generalizable technique to rapidly produce a range of MOFs, including UiO-66-NH₂, UiO-66, HKUST-1, and ZIF-L, under ambient, aqueous conditions. We further this understanding by tuning the labile metal node and deprotonated linker concentrations to produce space-time yields (STY) exceeding 2250 kg m^-3 day^-1, which is among the highest reported STYs for HKUST-1 and ZIF-L and an order of magnitude higher for aqueous zirconium-based MOF synthesis. Finally, we demonstrate UiO-66-NH₂ completes crystallization in 5 minutes at room temperature with 70% of crystallization of UiO-66-NH₂ occurs within 30 seconds, which is among the fastest reported reaction times in literature. With this work, we demonstrate a generalizable pathway for scaling MOF crystallization to high STY under mild and benign synthesis conditions and lay ground work for understanding the complex multi-step crystallization kinetics of MOFs.