Iodine Adsorption in Metal Organic Frameworks in the Presence of Humidity

Abstract

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of 85 Kr and 129 I 2 due to their volatility and long half-life. Efficient capture of 129 I 2 ( t 1/2 = 15.7 × 10 6 years) from the nuclear waste stream can help reduce the risk of releasing I 2 radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I 2 adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I 2 in the presence of water vapor are thus of great interest. Herein, we report on the I 2 adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I 2 within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine.