Many solids are heterogeneous on the half to one nanometer scale and are composed of disparate building blocks, layers, or frameworks containing pores or channels. Zeolites and mesoporous materials represent one such group and many others feature a strongly bonded or geometrically continuous "host" confining "guest" species. This project addresses the common energetic features of such confinement in unconventional frameworks containing Germanium, Phosphorous, and transition metals in clathrates such as silica clathrasils and Zintl-type intermetallic semiconductors. The materials have applications as catalysts, ion exchangers, thermoelectrics, and optical materials. They are important in the environmental transport of heavy metals and radionuclides. The unique Thermochemistry Facility welcomes collaborations and is active in educating students and postdoctoral scholars in applying thermodynamics to their own work. Calorimetry will provide the core of special topics courses, often with a hands-on component. The PI will host an international conference on high temperature materials chemistry. The research group is diverse in gender and ethnic, cultural and scientific background, and the PI is a role model as a successful senior woman scientist.
Many solids are composed of disparate building blocks, layers, or frameworks containing chemically reactive pores or channels. They feature a strongly bonded or geometrically continuous "host" confining "guest" species. By measuring the stability of these materials through advanced calorimetric techniques which measure the heat effects associated with structural and chemical changes in the solids, this project will advance both fundamental knowledge and applications of these materials. The materials have applications as catalysts, ion exchangers, thermoelectrics, and optical materials, and they are important in the environmental transport of heavy metals and radionuclides. The PI will host an international conference on high temperature materials chemistry. The research group is diverse in gender and ethnic, cultural and scientific background, and the PI is a role model as a successful senior woman scientist.
Normal solids are dense, with little free space between their atoms. In contrast, zeolites, mesoporous materials, and recently discovered metal organic frameworks (MOFs) possess structures with large interconnected pores: sometimes the unoccupied space increases the volume by an order of magnitude. These pores are used to confine guest molecules and carry out reactions such as the cracking of petroleum to gasoline. This grant ( DMR 0601892, titled "Energetics of Spatially Confined Solids", Principal Investigator: Alexandra Navrotsky) addresses the fundamental questions of energetics of such porous materials: how is their stability affected by their structure, how are guest molecules confined, and are many different porous structures energetically competitive and accessible? Using specialized and unique high temperature calorimetric techniques, Navrotsky’s group has measured the heat effects associated with formation and transformation of a number of porous materials containing silicon, aluminum, boron, phosphorus, gallium, germanium, and other metals and, recently, of one MOF. In all cases, the structures are only slightly less stable than dense materials, and many different structures have simlar energies, creating a rich energy landscape of possible materials for new applications. Water in the structures plays an important role in their stabilization. These techniques and concepts are being extended to other porous materials, including carbon nanotubes.
