The design of Zr metal-organic frameworks in the detection and neutralization of organophosphorus based nerve agents and pesticides

Abstract

Organophosphates are ubiquitous in uses ranging from chemical warfare agents (CWA’s) to detergents. In between these two extreme uses lie organophosphorus-based agrichemicals, primarily pesticides, which are applied in multi-tonne amounts each year. Metal-organic frameworks, especially the UiO-6x family, are known to interact, sequester, and/or break down organophosphate nerve gases. This thesis presents the synthesis and characterization of UiO-6x MOFs, comparing standing solvothermal with microwave methods, which appear (by powder Xray diffraction, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance (SS-NMR) analysis) to give equally high-quality products. Preparation of the UiO-6x MOFs were conducted using 1 molar equivalent of ZrCl4 to 1 equivalent of organic ligand in the presence of equal volumes of dimethyl formamide (DMF) and glacial acetic acid (GAA) for both solvothermal and microwave methods. Yields ranged from 41-63% for our synthesized MOFs (UiO-66, UiO-67 and UiO-67-bipy). The prepared MOFs are then reacted with organophosphate nerve agent simulants and agrichemicals in reactions followed by GC or HPLC; it appears that the studied agrichemicals are less-reactive than their chemical warfare agent equivalents with only (2-chloroethyl) phosphonic acid and glyphosate showing reactivity with UiO-67 and UiO-66 respectively whereas UiO-67-bipy was shown to nearly completely degrade/sequester dimethyl methylphosphonate. Also presented are preliminary SSNMR spectra on UiO-66 post-reaction with glyphosate. The line-broadening and restricted rotation that occurs on the combined spectrum suggests the pesticide is incorporated whole into the MOF without degrading.