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Synthetics lead to new ways to destroy nerve agents


This news story was published on January 12, 2014.
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Illustration of a portion of the porous structure of the MOF material NU-1000 (left) with a zoom in of the hexa-zirconium(IV)-cluster node (middle) that catalyzes the hydrolysis of methyl paraoxon (right). Source: Dr. Joseph Hupp, Northwestern University

Illustration of a portion of the porous structure of the MOF material NU-1000 (left) with a zoom in of the hexa-zirconium(IV)-cluster node (middle) that catalyzes the hydrolysis of methyl paraoxon (right). Source: Dr. Joseph Hupp, Northwestern University

FORT BELVOIR, Va. – New, rugged functional synthetic polymers could soon be available to better destroy nerve agents, saving the lives of warfighters, first responders and civilians. DTRA CB/JSTO-sponsored research at Northwestern University in Illinois has led to the design and construction of nanostructured materials that catalyze the destruction of molecular simulants of organophosphorous nerve agents (such as sarin).

These agents are deadly, in part, because they block neural signal transmissions (including transmissions to essential muscles, such as those responsible for breathing) that lead to immediate and long-term effects that are broad and complex and could end in a coma or death. Therefore, materials are needed that can act similarly rapidly to destroy these agents. In a recently published Angewendte Chemie International Edition article titled “Simple and Compelling Biomimetic Metal-Organic Framework Catalyst for the Degradation of Nerve Agent Simulants,” the researchers at Northwestern report polymeric catalysts that could be useful for destruction of these agents.

The work was done by postdocs Michael Katz and Joseph Mondloch under the joint direction of Drs. Joseph Hupp and Omar Farha. The team initially set out to build chemical structures resembling the active sites of enzymes known to be active for the hydrolytic degradation of nerve agents. The aim was to mimic the desirable activity of these sites, but with catalysts that are much more stable than typical enzymes. In particular, the team sought to design materials that could withstand extremes of temperature and pH (both acid and base), while retaining their effectiveness even after years of storage.

The team’s initial efforts yielded materials having good stability but poor activity. Many hours and high temperatures were required to achieve simulant decomposition. Acting on a hunch that the catalysts might perform better if positioned in a more porous environment, the team turned to a class of materials known as metal-organic frameworks (MOFs). While MOFs had previously been considered as candidate catalysts, they were considered too fickle structurally to survive under the chemical conditions used for simulant destruction. Fortunately, new chemistry and new design rules had yielded advanced MOFs having the ability to withstand temperatures as high as 450 degrees Celsius and as harsh as boiling solutions at pH zero. Initial work focused on a known class of compounds (the “UiO” series) developed in Norway and yielded reaction times of less than an hour half-lives at room temperature, as described in more detail in the recent publication cited above.

The team also realized that the observed catalysis must be occurring by a distinctly different molecular mechanism than used by conventional hydrolase enzymes. The salient features (open pores, exposed metal sites, bound water and hydroxide units) could all be improved upon by turning to a new MOF material, NU-1000, that the Northwestern researchers themselves had developed. This material yielded the as-yet-unpublished half-lives of 3 minutes at room temperature for hydrolytic destruction of the agent simulants.

A key question going forward is how effective the catalysts will be when tasked with destroying real nerve agents. This work is planned to be conducted by scientists at the U.S. Army Edgewood Chemical Biological Center (ECBC), since the handling of the nerve agents requires the use of special facilities along with the collaboration of technical experts, as the nerve agents are too dangerous to be handled in academic settings. Nevertheless, if NU-1000 or its successors prove similarly effective for degradation of real nerve agents, the materials might merit evaluation in field-deployable test systems.

Read more: http://www.dvidshub.net/news/119018/new-synthetics-lead-new-ways-destroy-nerve-agents#.UtI_zij3M20#ixzz2qALP0CY1

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