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

Robust and versatile metal–organic frameworks
(MOFs) have
emerged as sophisticated scaffolds to meet the critical needs of the
nuclear community, but their performance depends on their underexplored
structural integrities in high- radiation fields. The contributions
of selected metal nodes in the radiation stability of MOFs within
the isostructural M-UiO-66 series (where M = Zr, Ce, Hf, Th, and Pu;
Zr-UiO-66 experiments were executed in a previous work) have been
determined. Ce-, Hf-, and Th-UiO-66 MOF samples were irradiated via
gamma and He-ion methodologies to obtain doses up to 3 MGy and 85
MGy, respectively, the latter strikingly higher than that obtained
in most other studies. Appreciable self-irradiation constituted the
total absorbed doses, up to 31 MGy of the gamma-irradiated Pu-UiO-66
samples. Structural degradation was ascertained by powder X-ray diffraction,
X-ray total scattering, vibrational spectroscopy, and, where possible,
N2 physisorption isotherms. Diffuse reflectance infrared
Fourier transform spectroscopy provided atomic-level mechanistic insights
to reveal that the node-linker connection was most susceptible to
radiation damage. Density functional theory calculations were performed
on cluster models to evaluate the binding energy of the linkers to
each metal node. While the isostructures disclosed the same breakdown
signatures, distinct radiation sensitivity as a function of metal
selection was evident and followed the trend Hf-UiO-66 ∼ Zr-UiO-66
> Th-UiO-66 > Pu-UiO-66 > Ce-UiO-66. We anticipate that these
endeavors
will contribute to the rational design of radiation-resistant materials
for targeted applications.