ic7b02019_si_001.pdf (226.42 kB)
Porous Uranium Diphosphonate Frameworks with Trinuclear Units Templated by Organic Ammonium Hydrolyzed from Amine Solvents
journal contribution
posted on 2017-10-17, 18:48 authored by Zhi-Hui Zhang, Ganna A. Senchyk, Yi Liu, Tyler Spano-Franco, Jennifer E. S. Szymanowski, Peter C. BurnsBy varying solvent systems, the solvothermal
treatment of uranyl nitrate and methylenediphosphonic acid (H4PCP) afforded three new porous uranyl-organic frameworks (UOFs).
All were structurally characterized by single-crystal X-ray diffraction
and formulated as (Et2NH2)2[(UO2)3(PCP)2](H2O)2.5 (1), (MeNH3)(H3O)[(UO2)3(PCP)2(H2O)3] (2), and [Na(H2O)4](H3O)[(UO2)3(PCP)2(H2O)2](H2O)5 (3). These compounds crystallize with three-dimensional
anionic frameworks containing U(VI) and distinct cationic species
due to in situ solvent hydrolysis. The solvent systems diethylformamide (DEF), N-methyl-2-pyrrolindone
(NMP), and the additive sodium vanadate (Na3VO4) significantly impact the resultant structures, affording diethyl
ammonium, methyl ammonium, and sodium cations captured in channels
of the anionic frameworks of 1–3.
In 1, a trinuclear U3O18 unit formed
by three uranyl polyhedra that share edges is connected into a three-dimensional
framework. Compound 2 has a three-dimensional framework
formed from a uranyl-methylenediphosphonate layer that is pillared
by UO7 pentagonal bipyramids. With the inclusion of sodium
cations, 3 is a porous framework containing UO7 pentagonal bipyramids within a layer, with sodium cations and UO6 square bipyramids linking the adjacent layers. Compounds 1–3 feature the uranyl/ligand ratio of
3:2, but present diverse structural building units ranging from edge-shared
trinuclear to heteronuclear assemblies. The compounds have been characterized
by infrared (IR), Raman, and UV–vis spectroscopies, X-ray diffraction,
and thermogravimetric analysis.
