Kinetics and mechanisms of ZnO to ZIF‐8 transformations in supercritical CO2 revealed by in situ X‐ray diffraction

ZIF-8 was synthesized in supercritical carbon dioxide (scCO 2 ). In situ powder X-ray diffraction, ex situ microscopy, and simulations provide a encompassing view of the formation of ZIF-8 and intermediary ZnO@ZIF-8 composites in this nontraditional solvent. Time-resolved imaging exposed divergent physicochemical reaction pathways from previous studies of the growth of anisotropic ZIF-8 core@shell structures in traditional solvents. Synthetically relevant physiochemical properties of scCO 2 were integrated into classical nucleation theory, relating interfacial forces, calculated through DFTB+ based MD, with 3D nucleation outcomes. The kinetics of crystallization were examined and displayed a characteristic signature of time- and temperature-dependent mechanisms over the extent of the reaction. Lastly, we show that subtle factors, such as the extent of reaction and the size/shape of sacrificial templates can tailor ZIF-8 composition and size, eliciting control over hierarchical porosity in a nonconventional green solvent.