Adsorption-Induced Optical Modulation in ZIF Thin Film Stacks with Distinct Order for Photonic Crystal Applications

Due to their high chemical and thermal stability, zeolitic imidazolate frameworks (ZIFs) are interesting materials for various applications. To adapt ZIFs for new applications, such as optics, it is necessary to achieve precise shaping and control over film formation. Thin films are ideal for this purpose, as several of them are commonly used in optical devices. Here, we present a variety of different ZIF thin films that are accessible by applying a ZIF-8 seeding layer approach. High-quality ZIF-8 thin films are used as a seeding layer for the rapid production of other ZIF layers. All ZIFs are provided in high optical quality and have been characterized with respect to their optical properties. The presented thin films can also be fabricated as stacked layers with the desired order of different ZIFs to form photonic crystal structures, such as Bragg-stacks. Depending on the system, the fabrication of the stacked layers takes only a few hours. Finally, the thin films are loaded with guest molecules to influence their optical properties. Subsequent selective loading of the pores in ZIF 8/ZIF 90 stacks was achieved by using guest molecules of different polarity.