Detection of iodine species is important for the safety of the population in cases of nuclear accidents or advanced nuclear fuel reprocessing. Here we leverage the selective sorption of I₂ by metal organic framework (MOF) ZIF-8 to create an impedance spectroscopy-based sensor for the real-time detection of gaseous I₂. Methanolic ZIF-8 suspensions were cast onto interdigitated electrodes, dried, and exposed to gaseous I₂ at 25, 40, or 70 °C. Equivalent circuit models were developed to separate the response of the extremely resistive ZIF-8 from that of the underlying glass substrate. While high fidelity measurements enable electrical characterization of pure ZIF-8, such precision is woefully unnecessary to detect I₂; a >10⁵× decrease in ZIF-8 resistance was observed upon sorption of 116 wt% I₂ by ZIF-8 at 70 °C. Such large changes in impedance open the door for I₂ detection schemes using inexpensive electronics. Tests for interfering gases such as air, argon, methanol, and water revealed minimal changes in impedance and equivalent circuit response. Using an unoptimized sensor geometry, I₂ was readily detected at 25 °C in air. Further optimization of sensor geometry, decreasing MOF film thicknesses and maximizing sensor capacitance, will enable faster detection of trace I₂, providing a rapid, robust, and reliable iodine sensor for the safety of the populace.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.