Incorporating Transition Metal Ions into Uranium Oxide Hydrates: The Role of Zn(II) and the Effect of the Addition of Cs(I) Ions.

The synthesis of two zinc-bearing uranium oxide hydrate (UOH) materials has been achieved, and their crystal structures, obtained via single-crystal X-ray diffraction using synchrotron radiation, and additional structural and spectroscopic properties are reported herein. Although both structures incorporate Zn cations, the two differ significantly. The compound Zn(OH)(HO)[(UO)UO(HO)] (), forming a framework-type structure in the 1̅ space group, was composed of β-UO layers pillared by uranyl polyhedra, with the Zn cations incorporated within the framework channels.

Uranium Oxide Hydrate Frameworks with Dy(III) or Lu(III) Ions: Insights Into the Framework Structures With Lanthanide Ions.

Two uranium oxide hydrate frameworks (UOHFs) with either Dy or Lu ions, Dy(HO)[(UO)UO(OH)] (UOHF-Dy) or Lu(HO)[(UO)UO(OH)] (UOHF-Lu), were synthesized hydrothermally and characterized with a range of structural and spectroscopic techniques. Although SEM-EDS analysis confirmed the same atomic ratio of ~5.5 for U : Dy and U : Lu, they displayed different crystal morphologies, needles for UOHF-Dy in the orthorhombic C222 space group and plates for UOHF-Lu in the triclinic P-1 space group.

Filling the gaps of uranium oxide hydrates with magnesium(II) ions: unique layered structures and the role of additional sodium(I) ions.

Alkaline earth metal ions play an important role in the formation of secondary uranium minerals due to their abundance in the Earth's crust. Although uranium oxide hydrate (UOH) minerals and synthetic phases with calcium, strontium and barium ions have been investigated, their counterparts with magnesium ions are much less studied. In this work, synthetic UOH materials with magnesium ions have been investigated with three new compounds being synthesised and characterised.

Exploring the influence of pH on the structural intricacies of uranium oxide hydrates containing both Cd(II) and K(I) ions.

We report the synthesis of two new dual-cation uranium oxide hydrate (UOH) materials, containing both Cd and K ions, along with their characterisation by means of single-crystal X-ray diffraction and a range of other structural and spectroscopic techniques. The materials were found to differ in structures, topology and uranium to cation ratios, with the layered UOH-Cd crystallising in a plate morphology and containing a U : Cd : K ratio of 3 : 1.5 : 1.

Uranium oxide hydrate frameworks with Er(III) or Y(III) ions: revealing structural insights leading to the low symmetry.

Two new mixed-valence uranium oxide hydrate frameworks (UOFs), incorporating either Er or Y ions, were successfully synthesised under hydrothermal conditions and characterised with single-crystal X-ray diffraction and a variety of other structural and spectroscopic techniques. Both frameworks are isostructural and crystallise in the triclinic 1̄ space group, consisting of β-UO type layers pillared by additional uranyl centres, with the Er/Y ions lying in the channels of the framework. SEM-EDS analysis found that both materials existed in plate-like morphologies, with a U:Er/Y ratio of 5.

Synthetic uranium oxide hydrate materials: Current advances and future perspectives.

Uranium oxide hydrate (UOH) materials, a group of minerals and synthetic phases, have attracted recent attention due to their high structural flexibility and diversity as well as their primary relationship with natural weathering of the mineral uraninite and the alteration of spent nuclear fuel (SNF) in geological disposal. Due to the limited structural and chemical understanding of UOH minerals, synthetic UOH phases provide a unique opportunity to fill existing knowledge gaps through the exploration of further structural diversity and distinctive properties, as well as potential applications. Some of the latest developments of synthetic UOH phases include the incorporation of 3d transition metal and lanthanide ions, the evolution of uranyl oxide hydroxide layers driven by interlayer charge, the structural diversity of uranyl oxide hydrate frameworks, and the intrinsic driving force for the formation of diversified structural types.

Hydrothermal Syntheses of Uranium Oxide Hydrate Materials with Sm(III) Ions: pH-Driven Diversities in Structures and Morphologies and Sm-Doped Porous Uranium Oxides Derived from Their Thermal Decompositions.

We report the hydrothermal syntheses of three uranyl oxide hydroxy-hydrate (UOH) materials containing Sm(III) ions () by controlling the solution pH and a new way to make Sm-doped porous uranium oxides with different U-to-Sm atomic ratios via their thermal decompositions. While layer-structured phases with U-to-Sm atomic ratios of 1 () and 4 () were obtained from the reaction of schoepite and samarium nitrate with final solution pH values of over 4, similar reactions without pH adjustment with final solution pH values of less than 4 led to the formation of a uranyl oxide framework () with a U-to-Sm atomic ratio of 5.5.

Uranyl oxide hydrate frameworks with lanthanide ions.

Two uranyl oxide hydrate frameworks (UOFs) incorporating either Eu(iii) or Gd(iii) ions were synthesized hydrothermally and structurally studied. The uranyl oxide hydroxide layers similar to those in β-U3O8 with both tetragonal and pentagonal bipyramidal uranium polyhedra are connected with pairs of pentagonal bipyramidal uranium polyhedra through uranyl cation-cation interactions to form three-dimensional frameworks with Eu(iii) or Gd(iii) ions inside the channels. Both SEM and TEM examinations revealed needle crystal morphologies and a U:Eu/Gd ratio of 5.

[U(HO)]{[(UO)O(OH)][(UO)(HO)]}: A Mixed-Valence Uranium Oxide Hydrate Framework.

A uranium oxide hydrate framework, [U(HO)]{[(UO)O(OH)][(UO)(HO)]} (), was synthesized hydrothermally using schoepite as a uranium precursor. The crystal strucutre of was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron miscroscopy. The typical uranyl oxide hydroxide layers similar to those in β-UO are further connected via double-pentagonal-bipyramidal uranium polyhedra to form a three-dimensional (3D) framework structure with tetravalent uranium species inside the channels.

Layer-structured uranyl-oxide hydroxy-hydrates with Pr(iii) and Tb(iii) ions: hydroxyl to oxo transition driven by interlayer cations.

We report the hydrothermal synthesis and characterization of two uranyl-oxide hydroxy-hydrate compounds with Pr(iii) (U-Pr) and Tb(iii) (U-Tb) ions prepared via direct hydrothermal reactions of lanthanide (Ln = Pr or Tb) ions with a uranyl-oxide hydroxy-hydrate phase, schoepite. Both compounds U-Pr and U-Tb show thin plate morphologies with atomic ratios of 2 (U : Pr) and 6 (U : Tb) and have been characterized by multiple techniques. The layered structures with interlayer hydrated Pr(iii) or Tb(iii) ions formed via uranyl-Pr/Tb interactions have been confirmed by synchrotron single crystal X-ray diffraction studies.