(701c) Process Elucidation and Hazard Analysis of Metal-Organic Framework Scale-up Synthesis: A Case Study of ZIF-8

Benefitting from their unique porous structure and components at the atomic level, metal-organic frameworks (MOFs) have attracted increased attention for use in various applications, including catalysis, separation, environment, food, and medicine. Guidelines for efficient and safe scale-up synthesis of MOFs are significant to industry, therefore, a detailed process kinetics and hazard analysis can provide an inherently safe design before actual implementation. In this work, from a perspective of reaction engineering and process safety, zeolitic imidazolate framework-8 (ZIF-8) is selected as a case example to study MOF scale-up synthesis in a solvothermal RC1e reactor coupled with in-situ FTIR spectroscopy under room temperature. Various stages of ZIF-8 formation at room temperature, including nucleation, growth, and stationary, were investigated to identify the 2-methylimidazole concentration evolution over time. Avrami’s equation was then used to correlate reaction kinetics based on the obtained concentration results. The reaction temperature and heat release behaviors were also simultaneously identified to prevent inconsistent product properties from resulting in thermal runaway when scaling up the ZIF-8 production from the milliliter scale to liter scale. Product properties were compared among varied ZIF-8 products using PXRD, N₂ adsorption, and DLS. A group of biological toxicity tests and process HAZOP analysis were conducted, and it was determined that the hazards present in the MOF scale-up synthesis process can be efficiently managed using the prevention-mitigation-response strategy.