Phase Control and Transformations of Azole-Based Metal Organic Framework Composites

Abstract

Zinc-azole-based metal organic frameworks (MOFs) have been demonstrated to exist in a wide variety of structural states, with applications in different fields such as gas separation. In this dissertation, we explore the phase control and dynamics of zinc-azolebased MOFs in crystalline, liquid, and glassy states. We first study ZIF-7 phase control using mechanochemical synthesis. Ammonium nitrate was found to be a good catalyst in mechanochemical ZIF formation, with the usage of DMF and H2O favouring ZIF-7-I and ZIF-7-III formation, respectively. New phases of ZIF-7 variations not accessible using the solvothermal method were also obtained mechanochemically indicating the possibility of a new mechanochemical synthesis route. The mechanochemical ZIF-7 mixed matrix membrane (MMM) demonstrates good CO2- based selectivity improvements. Next, we demonstrate the formation of a new meltable zinc-azole framework (ZnCP) with liquid crystal behaviour by the addition of orthophosphate. ZnCP was able to melt at a low temperature while retaining and orienting its crystallinity into transparent liquid, thus showing promising use in optical-based applications. This material can also be obtained using a top-down approach by adding phosphoric acid to ZIF-7. Controlling phosphoric acid incorporation results in different melted ZnCP particle ratios, which was explored as a gas separation membrane. We then explore the effect of silver (Ag) composite presence on the thermal dynamics of another zinc-azole framework (ZIF-62). The benzimidazole amount within the Ag-doped ZIF-62 structure affects its thermal conversion, forming either Ag-doped ZIF-zni or Agdoped ZIF glass. The thermal dynamics of Ag-doped structures were explored using both in-situ (thermal) and ex-situ techniques. Both Ag-doped phases were demonstrated to have good MMM separation improvements for CO2 and light hydrocarbon, indicating the accessibility of the silver composite. Lastly, a quick demonstration of new methods (dip and spin coating) to process ZIF-62 and ZIF-62 composite successfully forms continuous particle dispersion, allowing the formation of a continuous glass layer. Different compositions such as sandwiched structure and layer by layer were explored, with advantages outlined. The novelty of this dissertation lies within the exploration of new synthetic methods and thermal dynamics to form structurally diverse zinc-azole MOFs which will be beneficial in the understanding of phase transformations in MOFs