Luminescent, porous, metal-organic crystals: Design, synthesis, and applications

The work presented in this thesis is focused on the design and discovery of new luminescent, porous, crystalline materials for targeted applications. In particular, we focus on luminescent Metal-Organic Frameworks (MOFs) and Organic Molecules of Intrinsic Microporosity (OMIMs), both belonging to emerging classes of synthetic materials that are particularly promising due to their porosity, modularity, and the many dynamic photophysical processes that can be exploited within them. While there is great potential for these types of materials, their relatively recent discovery, less than two decades prior to the writing of this thesis, means that they are still in early stages of development and so very few examples exist that demonstrate the potential for real-world applicability. Challenges persist in achieving targeted design, high stability, or processing for integration into devices. The aim of this thesis is consider new ways of strategically designing MOFs and OMIMs that may be carried a step closer to real-world application. With problems like excess energy consumption and the depletion of clean air and water supplies on the rise in today’s world, applications that can have a positive impact on the environment are of particular interest. We present a luminescent MOF that is capable of detecting trace amounts of fluoride contaminations in drinking water down to the parts per billion (ppb) range. The interactions of this MOF with fluoride in aqueous solutions are simultaneously electrostatic and specific in nature because of the carefully designed structure of its active site. This allows the material to be easily regenerated and used over 10 cycles, setting it apart from most existing molecular and polymeric fluoride sensors. We combined our MOF with a portable prototype sampling device that was designed and built in-house to measure fluoride concentrations in natural groundwater samples taken from three different countries, with the results showing excellent agreement with ion chromatography analysis. The strategy that we use to obtain this reversible yet selective interaction can be applied to the design of new MOFs that work on a similar principle. In addition, we present a new OMIM that exhibits broad spectrum, tuneable white light emission. The structural components and pore environment of the OMIM contribute to it having a high quantum yield in addition to tuneability that can be controlled by guest molecules. Using this material, we obtain the highest thus-far reported value of photoluminescence quantum yield for a single-species white-light emitter, with a nearly pure-white emission colour. This has promising implications for the fabrication of new, energy-efficient Organic Light-Emitting Diode (OLED) devices. In addition, introducing structural changes to the base ligand of this OMIM will allow us to obtain a greater range of colour tuneability as well as new features of guest-host chemistry.