(424c) Evaporation Governs the Formation of Thin-Film Metal Organic Frameworks: An in-Situ Experiment Combined Microkinetic Study

Thin-film metal-organic frameworks (MOFs) are gaining popularity due to their numerous applications in catalysis, sensing, storage, and separation. They have been made using a variety of methods, one of which is the synthesis using solution shearing-based evaporative crystallization. Although the impact of various variables was investigated experimentally, a theoretical understanding is essential to optimize the synthesis of MOFs and achieve better control over their properties. There haven't been any prior reports on the theoretical underpinnings of the synthesis of thin-film MOFs. In this study, a microkinetic model with multiple parameters was created to better understand the nucleation and growth mechanisms of the thin film MOF UiO-66 using data from time-resolved in-situ X-ray scattering experiments. Parameters such as temperature, rate constants, the number of available sites for the attachment of metal-ligand and organic linkers in the bulk solution, and the sites on adsorbed growth units on the substrate govern the reaction dynamics. Additionally, we noticed that the first layer created on this substrate has different reaction dynamics from the subsequent layers. Temperature-induced competition between evaporation and rates ultimately controlled the crystalline fraction and thickness, while the size distribution was controlled by the dynamics of the first layer. In conclusion, a micro-kinetic model was developed that can provide insights into the growth of MOF thin films and predict the optimal conditions for their synthesis. This model can be used to design new MOF thin films with specific properties for various applications.