The Mechanism of Rapid and Green Metal-Organic Framework Synthesis by In Situ Spectroscopy and Diffraction

Room-temperature aqueous synthesis provides facile access to metal-organic frameworks (MOFs) through green routes, avoiding the use of toxic solvents at high temperatures that are typical for common solvothermal MOF synthesis routes. Nevertheless, mechanisms of green aqueous MOF syntheses remain unexplored, hindering their further development. In this work, we for the first time report a comprehensive investigation of the synthesis of a MOF, Zn-MOF-74 (also known as CPO-27-Zn), in aqueous phase at room temperature. Using a unique combination of in situ infrared spectroscopy (IR) and high-energy X-ray diffraction (XRD), we reveal mechanistic insights into the fast synthesis (2-10 min) of Zn-MOF-74 from different sources, zinc acetate, and zinc perchlorate, at six different temperatures from 5 to 40 degrees C. A 5-fold acceleration was observed when using the noncoordinating perchlorate ion, making it an alternative precursor to decrease synthesis time. Furthermore, a correlation between IR and XRD data was established, allowing to monitor nucleation and growth processes individually with both techniques. Last, the particle size and shape distribution was linked to the differences in mechanistic kinetic parameters, allowing for their control by the choice of synthesis temperature and precursors.