Effects of High Gamma Doses on the Structural Stability of Metal–Organic Frameworks

Abstract

Four different MOFs were exposed to γ rays by a cobalt-60 source reaching a maximum dose of 5 MGy. The results showed that the MIL-100 (Cr) and MIL-100 (Fe) did not exhibit obvious structural damage, suggesting their excellent radiation stability. MIL-101 (Cr) showed good radiation stability up to 4 MGy, but its structure started degrading with increasing radiation dose. Furthermore, the results showed that the structure of AlFu MOFs started to decompose at a gamma dose of 1 MGy, exhibiting a much lower tolerance to γ radiation. At this radiation energy, the dominant interaction of the gamma-ray with MOFs is the Compton effect and the radiation stability of MOFs can be improved by prolific aromatic linkers, high linker connectivity, and good crystallinity. The results of this study indicate that MIL-100 and MIL-101 MOFs have a good potential to be employed in nuclear applications, where relatively high radiation doses play a role, for example, nuclear waste treatment and radionuclides production.

Role of Metal Selection in the Radiation Stability of Isostructural M-UiO-66 Metal–Organic Frameworks

“…This conclusion is also supported by the findings of Gilson et al. , Elsaidi et al , and Ma et al In our system, the cross-section prediction would place Ce-UiO-66 right behind Zr-UiO-66 as the strongest in the stability trend, which disagrees with our experimental results showing Ce-UiO-66 to be the weakest of the series. Energy losses by gamma rays are through Compton interactions, which are described by the photon adsorption cross sections, but the majority of the radiation damage is due to the cascading secondary electrons that interact with the medium through electronic interactions in the same manner as occurs with He ions.…”

“…While the metal absorption cross section is likely a contributing factor, alone it is inadequate as a determinant for MOF radiation stability. This conclusion is also supported by the findings of Gilson et al, 29 Elsaidi et al, 2 and Ma et al 41 In our system, the cross-section prediction would place Ce-UiO-66 right behind Zr-UiO-66 as the strongest in the stability trend, which disagrees with our experimental results showing Ce-UiO-66 to be the weakest of the series. Energy losses by gamma rays are through Compton interactions, which are described by the photon adsorption cross sections, but the majority of the radiation damage is due to the cascading secondary electrons 56,58 Zr > Ce > Hf > Th > Pu 1.202 > 1.266 > 1.601 > 1.628 > 1.704 metal ionic radius, CN = 8 (Å) 86 Hf > Zr > Pu > Ce > Th 0.83 > 0.84 > 0.96 > 0.97 > 1.05 Pauling electronegativity of metal 87,88 Zr > Hf ∼ Th > Pu > Ce that interact with the medium through electronic interactions in the same manner as occurs with He ions.…”

“…Pinpoint studies of irradiated MOFs have observed general reduction in crystallinity, surface roughening, and, where accessible, changes in the apparent surface area. 18,28,33,41 Volkringer et al 18 describe a gamma irradiation study of model MOFs�ZIF-8, HKUST-1, MILs (MIL-53, MIL-100, and MIL-120), and UiO-66. These are composed of different metals, Zn 2+ , Cu 2+ , Al 3+ , and Zr 4+ , respectively, and while there is some overlap of linkers between structures, the ultimate nodal connectivities, ergo topologies, are different.…”

“…Many reports discuss thermal, chemical, and mechanical stability of MOFs, yet relatively few examine their radiation stability. ,− Furthermore, results of previous studies are difficult to compare as they are collectively scattered in both MOF selection and irradiation methodology (see Table S1) and could benefit from more systematic approaches with well-defined variables. Pinpoint studies of irradiated MOFs have observed general reduction in crystallinity, surface roughening, and, where accessible, changes in the apparent surface area. ,,, Volkringer et al describe a gamma irradiation study of model MOFsZIF-8, HKUST-1, MILs (MIL-53, MIL-100, and MIL-120), and UiO-66. These are composed of different metals, Zn 2+ , Cu 2+ , Al 3+ , and Zr 4+ , respectively, and while there is some overlap of linkers between structures, the ultimate nodal connectivities, ergo topologies, are different.…”

Selective Crystallization of a Highly Radiation-Resistant Isonicotinic Acid-Based Metal–Organic Framework as a Primary Actinide Waste Form

“…Both particle morphology (Figure c) and elemental composition of irradiated samples (Figure S8) are consistent with those in the pristine specimen. This is one of the highest β- or γ-irradiation doses, to our knowledge, that any MOF material can so far tolerate, − despite that they are a few magnitudes lower than the estimated absorbed dose (10 8 –10 11 Gy) for spent nuclear fuel in a geological repository after 10 6 years . Such remarkable radiation resistance is ascribed to its structural feature: (i) geometrically close highly Lewis acidic thorium hexamer connected by the prolific aromatic linker per volume unit and (ii) radiations adsorbed by the Th 6 node will propagate to dangling INA, DMF, or H 2 O located at metal hexamers.…”