Northwestern scientists have developed a robust new material, inspired by biological catalysts, that is extraordinarily effective at destroying toxic nerve agents that are a threat around the globe.
First used 100 years ago during World War I, deadly chemical weapons continue to be a challenge to combat. The material, a zirconium-based metal-organic framework (MOF), degrades in minutes one of the most toxic chemical agents known to mankind, Soman (GD), a more toxic relative of sarin. Computer simulations show the MOF should be effective against other easy-to-make agents, such as VX.
The catalyst is fast and effective under a wide range of conditions, and the porous MOF structure can store a large amount of toxic gas as the catalyst does its work.
These features make the material promising for use in protective equipment worn by soldiers, such as gas masks, and for destroying stockpiles of chemical weapons. This designed material is very thermally and chemically robust, and it doesn’t matter what conditions it is in. It can be in water or in a very humid environment, at a temperature of 130 degrees or minus 15, or in a dust storm. A soldier need not worry under what conditions his protective mask will work. We can put this new catalyst in rugged conditions, and it will work just fine.
MOFs are very porous, so they can capture, store and destroy a lot of the nasty material, making them very attractive for defense-related applications. Simple changes to the nerve agent’s molecular structure can change something that can kill a human into something harmless. GD and VX are not very sophisticated agents, but they are very toxic. With the correct chemistry, we can render toxic materials nontoxic.
Metal-organic frameworks are well-ordered, lattice-like crystals. The nodes of the lattices are metals, and organic molecules connect the nodes. Within their very roomy pores, MOFs can effectively capture gases, such as nerve agents.
The Northwestern MOF, called NU-1000, has nodes of zirconium, the active catalytic site where all the important chemistry takes place. The organic ligand gives the material its important structure by connecting the nodes, but it does not participate in the catalysis of the nerve agent. The zirconium node selectively clips the phosphate-ester bond in the nerve agent, rendering it innocuous. With the critical bond broken, the rest of the molecule is left alone. The bond is broken through the process of hydrolysis, a reaction involving the breaking of a molecule’s bond using water. The MOF can use the humidity in the air.
In their study, the researchers first tested their catalyst against a GD simulant, called DMNP, and found the MOF degraded half of the target in less than 90 seconds.
Next, they tested the MOF against GD and found the catalyst degraded half of the nerve agent in less than three minutes.
These half-lives are very impressive, and show how well the catalyst is working.
For more information please visit: www.northwestern.edu
