(77a) Controlling Metal Organic Framework Thin Film Crystallization Using Confinement and Interface Engineering

Metal organic frameworks (MOFs) are periodic, highly porous materials that are made by combining metal ion clusters with organic linkers. The diversity available in metal ions as well as organic linkers can be used to create numerous MOFs, with thousands of structures already synthesized over the past two decades. Due to their chemical tunability as well as the control over pore size, shape and volume, MOFs have been studied for a wide variety of applications, including gas storage, separations, catalysis, energy storage, sensing and drug delivery. However, most of the research on MOFs have focused on controlling the chemical structure, and there is comparatively less work available on controlling the crystalline morphology of MOFs. For example, for many of the applications mentioned above, such as sensing, separations and charge/ion transport, it is beneficial for the MOF to be grown as thin films. These thin films can be created using numerous methods, layer-by-layer (LBL) being the most commonly used.

Our work utilizes chemical understanding of MOF growth and kinetic crystallization processes to accelerate MOF thin films and control MOF morphology and polymorphism. By controlling the interfacial conditions used during MOF growth, highly dense MOF films can be created on various surfaces. Controlling the nucleation density can also control the orientation of the MOF thin films, as shown with the NU-1000 MOF. We also show that thin films of UiO-66 can be created using interface engineering, at a time scale of seconds compared to conventional LBL methods, which take hours. Finally, these MOF thin films will be utilized as filtration devices and electrocatalysts due to the controllable diffusional characteristics.