NEW DEVELOPMENTS IN URANIUM-OXIDE CRYSTAL CHEMISTRY: MINERALS AS INSPIRATION FOR NOVEL SOLID-STATE COMPOUNDS

Several new uranyl (UO₂²⁺ containing) compounds have been synthesized based on inspiration from structural themes found in uranium oxide minerals. The novel uranyl molybdate, (C₂H₃N₃)UO₂Mo₂O₇, is found to have a sheet structure identical to that of iriginite [(UO₂)Mo₂O₇(H₂O)₂](H₂O), yet differs in its interlayer composition as a result of replacing bound H₂O molecules with a coordinated organic structure directing agent, 1,2,4-triazole (C₂H₃N₃).  Further, controlled oxidization of such organic species under hydrothermal conditions has been shown to influence uranium valency in Zn_0.5[(U⁵⁺)_2-x(U⁶⁺)_x(UO₂)₄(OH)₂(H₂O)_4-x(O_8+x)]·3.2H₂O. This material is a rare example of a U(V) compound and has a sheet structure related to that found in wyartite (CaU⁵⁺(UO₂)₂(CO₃)O₄(OH)(H₂O)₇).  Lastly, several new metal-organic-frameworks (MOFs) have been synthesized by tethering [(UO₂)O₆] hexagonal bipyramids, the fundamental building blocks of uranyl carbonate minerals, through dibasic carboxylic acids.