Heterometallic Ce IV /M oxo clusters are underexplored yet and can benefit from synergistic properties from combining cerium and other metal cations to produce efficient redox catalysts. Herein, we designed and synthesized a series of new Ce 12 V 6 oxo clusters with different capping ligands: Ce 12 V 6 -SO 4 , Ce 12 V 6 -OTs (OTs: toluenesulfonic acid), and Ce 12 V 6 -NBSA (NBSA: nitrobenzenesulfonic acid). Single crystal X-ray diffraction (SCXRD) for all three structures reveals a Ce 12 V 6 cubane core formulated [Ce 12 (VO) 6 O 24 ] 18+ with cerium on the edges of the cube, vanadyl capping the faces, and sulfate on the corners. While infrared spectroscopy (IR), ultraviolet−visible spectroscopy (UV− vis), electrospray ionization mass spectrometry (ESI-MS), and proton nuclear magnetic resonance ( 1 H NMR) proved the successful coordination of the organic ligands to the Ce 12 V 6 core, liquid phase 51 V NMR and small-angle X-ray scattering (SAXS) confirmed the integrity of the clusters in the organic solutions. Furthermore, functionalization of the Ce 12 V 6 core with organic ligands both provides increased solubility in term of homogeneous application and introduces porosity to the assemblies of Ce 12 V 6 -OTs and Ce 12 V 6 -NBSA in term of heterogeneous application, thus allowing more catalytic sites to be accessible and improving reactivity as compared to the nonporous and less soluble Ce 12 V 6 -SO 4 . Meanwhile, the coordinated ligands also influenced the electronic environment of the catalytic sites, in turn affecting the reactivity of the cluster, which we probed by the selective oxidation of 2-chloroethyl ethyl sulfide (CEES). This work provides a strategy to make full use of the catalytic sites within a class of inorganic sulfate capped clusters via organic ligand introduction.
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 highradiation 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 Heion 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, N 2 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.
Metal-organic polyhedra (MOPs) are discrete molecules made of metal ions/clusters and organic ligands, and their crystal packing leads to the generation of intrinsic and extrinsic porosity. Due to their structural...
Metal-organic polyhedra (MOPs) are discrete molecules made of metal ions/clusters and organic ligands, and their crystal packing leads to the generation of intrinsic and extrinsic porosity. Due to their structural versatility, porosity, and nanoscale size, MOPs are considered an attractive platform for catalysis. In this study, we report for the first time the use of three zirconium(IV)-based MOPs for the degradation of trace concentrations of the nerve agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP). All three MOPs degraded DMNP instantaneously, with half-lives ranging from t1/2 = 17 to 130 s. The catalytic activity of MOPs is thought to be due to (1) their periodic packing resulting in long-range order that creates extrinsic porosity, allowing DMNP to diffuse in and interact with the pore surface and Lewis acids (Zr(IV) centers) of MOPs, and (2) the lability of Zr-Cp (Cp = cyclopentadienyl) bond, allowing Cp ligands to rearrange and make space for DMNP to interact with the Zr(IV). The catalytic activity of MOPs is not deteriorated by increasing the concentration of the nerve agent simulant nor in consecutive catalytic experiments, highlighting their robustness as catalysts. Our study showcases the promise of MOPs as one of the fastest active catalysts for the instantaneous degradation of nerve agents.
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