Determining Diffusion Coefficients of Chemical Warfare Agents in Metal–Organic Frameworks

Metal–organic frameworks (MOFs) have shown potential
for
selective capture of chemical warfare agents (CWAs). To determine
characteristic adsorption times, the kinetics of CWA uptake in MOFs
must be known. Here, we calculate diffusion coefficients of the CWA
sarin and simulants in prototypical MOFs using classical molecular
simulations. Sarin can diffuse throughout a one micrometer crystal
in less than a second in MIL-47 and Cu-BTC, but this process takes
more than 3 h in ZIF-8 and UiO-66. A simple estimate based on Knudsen
diffusion is able to describe diffusion of sarin in MIL-47 but fails
to do so in other MOFs. This work has implications in designing devices
to detect and capture CWAs.