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

Abstract

Two new mixed-valence uranium oxide hydrate frameworks (UOFs), incorporating either Er3+ or Y3+ ions, were successfully synthesised under hydrothermal conditions and characterised with single-crystal X-ray diffraction and a variety of...

Exploring the influence of pH on the structural intricacies of uranium oxide hydrates containing both Cd(ii) and K(i) ions

“…Some of the previously published UOFs have been reported as existing in a mixed phase system, with the UOF present as the major phase. 23 In exploring the possible reason as to why the frameworktype structure was favoured during the UOF-Cd synthesis, the most apparent conclusion is the solution pH. Past research has shown the influence the solution pH has on the formation of UOH compounds.…”

“…Some of the previously published UOFs have been reported as existing in a mixed phase system, with the UOF present as the major phase. 23…”

“…30,43 Interestingly, the β-U 3 O 8 topology is overwhelming favoured in UOF materials, 20,23–26,44 likely due to the fact that the β-U 3 O 8 anion topology can accommodate multiple valence states of uranium, a necessity in UOFs which contain mixed U 5+ /U 6+ sites within their structure. 23–25 Moreover, in the studies by Zhang et al 43 and Rivenet et al , 30 wherein the uranyl polyhedra layers take on the β-U 3 O 8 layout, the interlayer cations (Tb 3+ /Ni 2+ ) act as pillars which separate the uranyl polyhedra sheets. Each cation ‘pillar’ exists as an isolated species with channels in between, creating a pseudo-UOF material.…”

“…18,19,39,43,45 The β-U 3 O 8 topology has been observed in a number of UOH minerals, [46][47][48][49][50] but much less in layered synthetic structures. 30,43 Interestingly, the β-U 3 O 8 topology is overwhelming favoured in UOF materials, 20,[23][24][25][26]44 likely due to the fact that the β-U 3 O 8 anion topology can accommodate multiple valence states of uranium, a necessity in UOFs which contain mixed U 5+ /U 6+ sites within their structure. [23][24][25] Moreover, in the studies by Zhang et al 43 and Rivenet et al, 30 wherein the uranyl polyhedra layers take on the β-U 3 O 8 layout, the interlayer cations (Tb 3+ /Ni 2+ ) act as…”

“…UOF materials containing Eu, Gd and Er, which have ionic radii comparable to those of Cd 2+ , have all been reported as singlecation systems. 23,25 The obvious difference is therefore the oxidation state of the secondary cation species. With the presence of the secondary cations also driven by charge balance, the monovalent K + is therefore required to stabilise the framework structure.…”