The Impact of Structural Defects on Iodine Adsorption in UiO-66

Abstract

Radioactive I2 (iodine) produced as a by-product of nuclear fission poses a risk to public health if released into the environment, and it is thus vital to develop materials that can capture I2 vapour. Materials designed for the capture and storage of I2 must have a high uptake capacity and be stable for long-term storage due the long half-life of 129I. UiO-66 is a highly stable and readily tuneable metal-organic framework (MOF) into which defect sites can be introduced. Here, a defective form of UiO-66 (UiO-66-FA) was synthesised and the presence of missing cluster moieties confirmed using confocal fluorescence microscopy and gas sorption measurements. The uptake of I2 vapour in UiO-66-FA was measured using thermal gravimetric analysis coupled mass spectrometry (TGA-MS) to be 2.25 g g−1, almost twice that (1.17 g g−1) of the pristine UiO-66. This study will inspire the design of new efficient I2 stores based upon MOFs incorporating structural defects.

Capture of Gaseous Iodine in Isoreticular Zirconium‐Based UiO‐n Metal‐Organic Frameworks: Influence of Amino Functionalization, DFT Calculations, Raman and EPR Spectroscopic Investigation

“…The addition of a second amino group holds that highest iodine content within the pores of UiO‐67‐(NH 2 ) 2 for the present series, with the value of 1211 mg/g, still without reaching the saturation after t =48 h. These uptake values are comparable to that measured under static conditions, of ZIF‐8 (1250 mg/g), [14] or that reported by Maddock et al. in the pristine UiO‐66 (1170 mg/g), [22] but lower to that of HKUST‐1 (1750 mg/g) [19] . The kinetic rates are identical for these two amino‐decorated UiO‐67 compounds, with k LDF values of ≈ 0.0320(2) h −1 .…”

“…This gain is drastically further enhanced when the biphenyl-dicarboxylate linkers are decorated by a simple amino group (À NH 2 ), with a value of 1071 mg/g without reaching saturation at t = 48 h, and a k LDF value of 0.0920(8) h À 1 (twice smaller that than of UiO-67). The addition of a second amino group holds that highest iodine content within the pores of UiO-67-(NH 2 ) 2 for the present series, with the value of 1211 mg/g, still without reaching the saturation after t = 48 h. These uptake values are comparable to that measured under static conditions, of ZIF-8 (1250 mg/g), [14] or that reported by Maddock et al in the pristine UiO-66 (1170 mg/g), [22] but lower to that of HKUST-1 (1750 mg/g). [19] The kinetic rates are identical for these two amino-decorated UiO-67 compounds, with k LDF values of � 0.0320(2) h À 1 .…”

“…In our study, a significant difference iodine mass uptake of + 45 % was observed for the UiO-66-NH 2 sample, despite of close S BET values for both our solids. Moreover, other studies dealing with the gaseous iodine sorption in a close cell (static conditions with an iodine excess) for the pristine UiO-66 reported much higher capacities ranging from 660 [24] up to 1170 mg/g after 72 h. [22] Such a disparity could be explained by the variable quantities of iodine used in the different studies. In fact, we worked with a total iodine amount of 38 mg (iodine rate of 0.8 mg I 2 h À 1 ) for about 30 mg of UiO-n sample (mass ratio close to 1), whereas the other authors reported larger iodine contents, with a mass ratio of 10 for I 2 related to UiO-n sample.…”

“…The redox I 2 !I 3 À conversion was unexpected in our system and was observed in a few previous studies, [24] but was not mentioned in other works. [22,26] This reaction will be further characterized by Raman and EPR spectroscopies.…”

Coordination Polymers and Metal-Organic Frameworks: Structures and Applications—A Themed Issue in Honor of Professor Christoph Janiak on the Occasion of His 60th Birthday

“…The metal-organic framework UiO-66 is formed from ZrCl 4 and terephthalic acid, and is a highly stable assembly. Yang, Schröder and coworkers have demonstrated the ability of a defective form of UiO-66 to take up I 2 , and this investigation is relevant to the uptake and storage of radioactive I 2 [2]. Additionally related to adsorption of toxic small molecules (in this case CS 2 ), Li and coworkers have described the conjugate bases of 4 ,4 ,4 ,4 [3].…”