Structural determination of a highly stable metal-organic framework with possible application to interim radioactive waste scavenging: Hf-UiO-66

Abstract

High resolution synchrotron radiation x-ray powder diffraction (HR-XRPD) combined with Hf L3edge extended x-ray absorption fine structure (EXAFS) allowed to determine the structure of Hf-UiO-66 metal-organic framework (MOF) showing that it is iso-reticular to Zr-UiO-66 MOF [J. Am. Chem. Soc. 130, 13850 (2008)]. Thermal gravimetric measurements (coupled with mass spectroscopy) and temperature dependent synchrotron radiation XRPD proved the high thermal stability of the new MOF. The Langmuir surface area (849 m 2 /g) combined with the high stability of the UiO-66 framework and with the high neutron absorption cross section of Hf suggest that among all microporous crystalline materials the new Hf-UiO-66 MOF possesses the physical and chemical requirements for the interim storage of radioactive waste in a much safer way than is currently available. The first results proving the synthesis of a MOF material with UiO-66 topology realized by B-containing linker are also reported, allowing a further improvement of the neutron shielding power of these class of materials.

Cerium-based metal organic frameworks with UiO-66 architecture: synthesis, properties and redox catalytic activity

“…23 Complete substitution of zirconium in the structure has also been reported. 16,24 MOFs containing the hexanuclear [M 6 O 4 (OH) 4 ] 12+ cluster are in fact known for a range of metal(IV) 55 cations, including Hf, U and Th. 25 For cerium(IV), the molecular hexanuclear cluster has been previously reported with sulfate, 26 acetylacetonate, 27 benzoate 28 and 1,2-phenyldiphosphonate ions.…”

Tuning Defects to Facilitate Hydrogen Storage in Core-shell MIL-101(Cr)@UiO-66(Zr) Nanocrystals

“…This indicates that there may be a competitive role between BDC linkers and HCOOH modulator, and the creation of too many defects would lower the BET surface area and pore volume, resulting in lower hydrogen storage capacities. Several approaches have been undertaken to identify the structural defects within UiO-66, such as the presence of symmetry forbidden reflections in PXRD patterns [27], less weight loss than expected during thermal decomposition [28], higher surface area and pore volume than theoretically expected [29], more O-H stretching bands from FTIR spectrum [30], unexpected split and weakened fingerprints in Raman spectrum [31]. In line with the weight loss approach, thermogravimetric analysis (TGA) has been employed to identify MOF structural defects [32][33][34].…”

5. Structural and electronic characterization of nanosized inorganic materials by X-ray absorption spectroscopies

“…For the three systems, this combined XRPD, EXAFS and DFT approach allowed a full interpretation of the EXAFS data in both hydroxylated and dehydroxylated forms [101,102,104,105]. Please note that IR spectroscopy was crucial to confirm this model as it allowed to observe the disappearance of the O-H stretching band in these materials.…”

“…Part (g): N 2 adsorption/desorption isotherm for Hf-UiO-66 at 77 K. Unpublished figure reporting data from [100-102, 104, 105]. try studies reported in Figure 5.12c,f, UiO-67 [102] and Hf-UiO-66 [104] show thermal and chemical stability similar to that of UiO-66 and exhibit the expected surface area, as determined by low temperature volumetric N 2 adsorption isotherms ( Fig. 5.12d,g).…”