The Study of Zirconium Hydroxide and Zirconium (IV) Metal-Organic Frameworks as Reactive Substrates for the Decomposition of Chemical Warfare Agents
Date of Award
Master of Science in Chemical Sciences (MSCB)
Dr. Mark Mitchell
Dr. Heather Abbott-Lyon
Dr. Michael Van Dyke
Nerve agents have been described by the Center for Disease Control and Prevention to be the most toxic and rapidly acting of chemical warfare agents. The present study investigates the efficacy of zirconium hydroxide, Zr(OH)4, and Zr(IV) Metal-Organic Frameworks (MOFs) in the uptake and decomposition of the gas phase nerve agent simulant dimethyl methylphosphonate, DMMP. This investigation was carried out using two different methods: 1) with the use of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) to examine the surface reaction between DMMP and the solid; and 2) using a flow reactor system that monitored gas phase reaction products produces by the surface reaction. The results show that Zr(OH)4, an amorphous, amphoteric substrate with a Brunauer-Emmeet-Teller (BET) surface area 462 m2/g greatly outperforms the MOFs, which have 2-6 times the surface area of Zr(OH)4, in both uptake and decomposition of DMMP. Zr(OH)4 acts as a reactive adsorbent which irreversibly binds the phosphorous-containing products from the reaction, in a manner similar to other solid oxides. However, Zr(OH)4 arguably shows the highest reactivity to date, especially for simple metal oxide substrates, in terms of the yield of gas phase products per unit area as well as showing a novel decomposition product containing a P-H moiety. Further investigation of Zr(OH)4 showed that pretreatment of the material by heating either with a flow of ultra-high purity N2 or under vacuum reduced both adsorption capacity and reactivity; and that post exposure heating led to further reaction including loss of phosphorous containing species from the surface.