This dissertation deals with the syntheses, optical characterization and optical application of metal-organic frameworks (MOFs). In the first part of this thesis, different MOF single crystals were synthesized. Different structures were investigated in which either the metal cations or the organic linker molecules were varied. The organic linker molecules were also modified by post-synthetic variation. In order to obtain precise refractive indices of these MOF single crystals, the immersion method was used. To the best of our knowledge, this method has not yet been used in the characterization of MOFs. Consequently, besides the measurements itself, the investigation of the suitability of the method was also part of the work. The second part of this thesis deals with the syntheses of Ce(IV)bdc CsPbBr3 SiO2 materials for use in light-emitting devices (LEDs). For this purpose, different synthesis routes were investigated and the materials obtained were subsequently tested for their stability and performance. For stability testing, the materials were processed into films and exposed to high-intensity illumination as well as elevated temperature and humidity. The aim is to increase the stability of perovskite while still maintaining their highly luminescent performance by embedding them into a MOF-material.