Zirconia-Based Aerogels for Sorption and Degradation of Dimethyl Methylphosphonate
Jeffrey W. Long, Christopher N. Chervin, Robert B. Balow, Seokmin Jeon, Joel B. Miller, Maya E. Helms, Jeffrey C. Owrutsky, Debra R. Rolison, Kenan P. Fears
Abstract
Inspired by recent breakthroughs with Zr(OH)4-type materials that decompose chemical warfare agents (CWAs), we explore aerogel forms of zirconium oxyhydroxide (ZrOxHy) as reactive sorbents for dimethyl methylphosphonate (DMMP), a common simulant for organophosphorous CWAs. Zirconia gels were synthesized using propylene oxide and aqueous ZrCl4, followed by supercritical-CO2 extraction to yield monolithic ZrOxHy aerogels. Subsequent calcination at temperatures ≥350 °C removes organic byproducts of the epoxide-based synthesis while preserving high specific surface area (up to 234 m2 g–1) and the aerogel-like, cocontinuous pore-solid structure. Infrared (IR) spectroscopy and 1H nuclear magnetic resonance spectroscopy confirm that ZrOxHy aerogels retain a high concentration of surface hydroxyls, even when heated to 600 °C and converted to nanocrystalline cubic/monoclinic ZrO2. We used in situ IR spectroscopy to probe the interactions of DMMP with a series of ZrOxHy aerogel powders, showing that DMMP rapidly decomposes by reacting with the hydroxyl-rich aerogel to form surface-bound Zr–OCH3 and bridging O–P–O species. We compare these results to those of related zirconia-type materials and discuss prospects and advantages of ZrOxHy aerogels for CWA mitigation.