Structural Features of Zirconium-Based Metal–Organic Frameworks Affecting Radiolytic Stability

Abstract

Metal–organic frameworks (MOFs) NU-1000 and UiO-66 are herein exposed to two different gamma irradiation doses and dose rates and analyzed to determine the structural features that affect their stability in these environments. MOFs have shown promise for the capture and sensing of off-gases at civilian nuclear energy reprocessing sites, nuclear waste repositories, and nuclear accident locations. However, little is understood about the structural features of MOFs that contribute to their stability levels under the ionizing radiation conditions present at such sites. This study is the first of its kind to explore the structural features of MOFs that contribute to their radiolytic stability. Both NU-1000 and UiO-66 are MOFs that contain Zr metal-centers with the same metal absorption cross section. However, the two MOFs exhibit different linker connectivities, linker aromaticities, node densities, node connectivities, and interligand separations. In this study, NU-1000 and UiO-66 were exposed to high (423.3 Gy/min, 23 min, and 37 s) and low (0.78 Gy/min, 4320 min) dose rates of 60Co gamma irradiation. NU-1000 displayed insignificant radiation damage under both dose rates due to its high linker connectivity, low node density, and low node connectivity. However, low radiation dose rates caused considerable damage to UiO-66, a framework with lower aromaticity and smaller interligand separation. Results suggest that chronic, low-radiation environments are more detrimental to Zr MOF stability than acute, high-radiation conditions.

Pyrene-based metal organic frameworks: from synthesis to applications

“…Since the use of pyrene-based MOFs can be advantageous for the capture of radioactive gases, their stability under radiation conditions at nuclear energy reprocessing sites is highly important. Hanna et al 225 investigated the radiolytic stability of NU-1000 by exposing gamma irradiation. The PXRD pattern of NU-1000 showed no change after both high and low irradiation dose, confirming the structural stability of the MOF.…”

Beyond structural motifs: the frontier of actinide-containing metal–organic frameworks

“… 137,142–146 Farha and coworkers recently studied radiation-induced damage on the example of two Zr-based MOFs as well as factors that could potentially affect the radiolytic stability such as ligand aromaticity and connectivity, metal node density and connectivity, as well as interligand distance. 146 The authors proposed that differences in the MOF's radiolytic stability could be applied for specific radiological applications ( e.g. , long-term storage versus scintillation sensors).…”

Stability and radioactive gaseous iodine-131 retention capacity of binderless UiO-66-NH2 granules under severe nuclear accidental conditions

“…Therefore, the UiO-66-NH 2 compound shows an improved stability versus gamma irradiation compared to the nonfunctionalized phase. 16,17 This resistance toward irradiation could be assigned to the ability of scavenger groups, such as amines, to neutralize radicals formed by ionizing radiation 34 and to stop radical reactions accelerating the three dimensional network break. The compressive mechanical strength of UiO-66-NH 2 granules was also unchanged (0.2±0.1 N) after gamma irradiation (Fig.…”

“…15 Finally, recent studies also proved the very good stability of selected MOFs versus ionizing radiations such as gamma ray. 16,17 In this last case, the resistance is assigned to the very low density of MOFs, limiting the interaction with the electromagnetic radiation. Several studies already proved the great efficiency of some MOFs for the capture and the immobilization of molecular iodine.…”