Development and illustration of a unified conceptual framework for the design of extended metal -organic structures.

This thesis reports the analysis of all 3-dimensional metal-organic frameworks (MOFs) in the Cambridge Structure Database (CSD) that has led to the development of the overarching principles which provide a conceptual foundation for understanding existing MOF structures to aid in synthetic design future MOF materials. These concepts aid in choosing the components necessary to achieve a precise framework or to tailor a given MOF material for a specific application. The utility of these concepts in the design, synthesis, and characterization of several new materials is presented throughout this thesis. The use building units which do not impart directional information (iron (II) and formate ions) in MOF structures illustrates that highly variable synthetic systems are impacted by non-framework components such as the identity of the guest species, resulting different MOF structures, Fe3(OOCH) 6·1NMP (MOF-187) and Fe3(OOCH)6·0.5DEF (MOF-188). This effect, while significant here, may only be crucial in systems with high degrees of freedom. In contrast, when more rigid building units are employed, as is the case with BPTC-4 and Co2(CO2)4 clusters, the number of potential structures decreases, allowing for estimation of the MOF structure(s). The exchange labile Co2(CO2) 4 clusters in Co2(BPTC)(H2O)5 • Gx (MOF-501) give rise to a non-reversible transformation from the kinetic product to the thermodynamically favored product of Co2(BPTC)(H 2O)(DMF)2 • Gx (MOF-502). Neither of these materials showed significant nitrogen sorption capacities, a property which is dependent on structural integrity upon guest removal. However, by capitalizing on the more rigid Cu2(CO2)4 paddle-wheels building units imparts structural rigidity and ultimately gives rise to permanent microporosity upon removal of the guest species in Cu2(BPTC)(H 2O)2·(DMF)3(H2O) (MOF-505). Indeed, sorption isotherms of MOF-505 reveal the presence of permanent microporosity and a significant H2 uptake capacity of 2.46 wt%. The synthesis and characterization of these materials; Co2(BPTC) (MOF-501 & 502) and Cu2(BPTC) (MOF-505), are presented. The final contribution of this thesis highlights the utility of reticular chemistry in the synthesis and more importantly characterization of Zn 4O(BBC)2·Gx (MOF-200) which is isoreticular with Zn4O(BTB)2·Gx (MOF-177). This isoreticular metal-organic framework (IRMOF) has shown record breaking microporosity of 5,090 m2/g and an unprecedented primitive unit cell of nearly 100,000 A3 which rivals that of small macromolecular structures.Ph.D.Inorganic chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125462/2/3192741.pd

Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.

The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ({sup 129}I) and technetium ({sup 99}Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research & Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for {sup 129}I and {sup 99}Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix and thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable isotopes I and Re as analogs to {sup 129}I and {sup 99}Tc. The results have confirmed our original finding that nanoporous Al oxide and its derivatives have high I sorption capabilities due to the combined effects of surface chemistry and nanopore confinement. We have developed a suite of techniques for the fixation of radionuclides in metal oxide nanopores. The key to this fixation is to chemically convert a target radionuclide into a less volatile or soluble form. We have developed a technique to convert a radionuclide-loaded nanoporous material into a durable glass-ceramic waste form through calcination. We have shown that mixing a radionuclide-loaded getter material with a Na-silicate solution can effectively seal the nanopores in the material, thus enhancing radionuclide retention during waste form formation. Our leaching tests have demonstrated the existence of an optimal vitrification temperature for the enhancement of waste form durability. Our work also indicates that silver may not be needed for I immobilization and encapsulation

Exploiting Interfacial Water Properties for Desalination and Purification Applications

Sandia is a multiprogram laboratory operated by Sandia Corporation