Metal-Organic Framework Polymer Hybrid Materials for Chemical Warfare Agent Degradation
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Metal-Organic Framework Polymer Hybrid Materials for Chemical Warfare Agent Degradation

  • Author(s): Kalaj, Mark
  • Advisor(s): Cohen, Seth M
  • et al.
Abstract

Since first discovered some two decades ago, metal-organic frameworks (MOFs) have shown interesting properties with regard to storage, separation, and catalysis applications. While MOFs have shown promise in these arenas over the years, a major shortcoming of these materials is their inherently crystalline form factor which hinders their applicational. To circumvent this issue, we have turned to the hybridization of MOFs with polymers in an effort to form a material that has the desired properties of the MOF and the flexibility of the polymer. In particular, we seek to develop novel textile based (nylon based or spray coated) MOF-polymer hybrid materials that are catalytically active against harmful organophosphorus chemical warfare agents (CWAs). Chapter 2 describes the synthesis of a MOF-nylon hybrid material through and interfacial postsynthetic polymerization (PSP) method. The hybrid material contains 29 weight percent MOF and shows catalytic activity against a CWA simulant. Importantly, the covalent MOF-nylon material displays about a seven-fold increase in activity compared to physically mixed controls. In Chapter 3, we screened a wide range of MOFs with varying organic functional groups to establish structure activity relationships (SAR) between MOF functional groups and CWA simulant degradation. The Zr-based MOF UiO-66 (UiO = University of Oslo) was synthesized with either mixed ligand functional groups or halogenated functional groups. We determined that the mixed ligand approach improves CWA activity by three-fold whereas the UiO-66-Iodine MOF displays a fourfold increase in activity. Through theoretical calculations, the increased activity in UiO-66-I was determined to be an artifact of halogen bonding with the CWA simulant. In Chapter 4, we combined the approaches from Chapter 2 and 3, by using the commonly known pseudohalogen isothiocyanate (NCS) functional group in UiO-66 to improve the catalytic activity against CWAs and covalent PSP sites. The UiO-66-NCS MOF was synthesized via postsynthetic modification (PSM) and displayed a ~20 fold increase in activity compared to the presynthetic MOF. More importantly, using amine terminated polypropylene oxides, MOF-polymer material was formed, and spray coated onto textile fibers. This material showed great durability and catalytic activity compared to physically mixed controls. Chapter 5 describes the room temperature synthesis of the commonly used UiO-66 MOF as well as a few functional groups derivatives. Starting from a UiO-66-F4 MOF with relatively labile ligands, postsynthetic exchange (PSE) with four different MOF ligands at room temperature in aqueous conditions was performed with almost complete ligand exchange. These MOFs were thoroughly characterized after PSE and maintained desired properties such as crystallinity and particle size or shape.

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