AUTHOR=Juillerat Christian A. , Kocevski Vancho , Besmann Theodore M. , zur Loye Hans-Conrad 

TITLE=Observation of the Same New Sheet Topology in Both the Layered Uranyl Oxide-Phosphate Cs11[(UO2)12(PO4)3O13] and the Layered Uranyl Oxyfluoride-Phosphate Rb11[(UO2)12(PO4)3O12F2] Prepared by Flux Crystal Growth

JOURNAL=Frontiers in Chemistry

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00583

DOI=10.3389/fchem.2019.00583

ISSN=2296-2646

ABSTRACT=<p>Single crystals of four new layered uranyl phosphates, including three oxyfluoride-phosphates, were synthesized by molten flux methods using alkali chloride melts, and their structures were determined by single-crystal X-ray diffraction. Cs<sub>11</sub>[(UO<sub>2</sub>)<sub>12</sub>(PO<sub>4</sub>)<sub>3</sub>O<sub>13</sub>] (<bold>1</bold>) and Rb<sub>11</sub>[UO<sub>2</sub>)<sub>12</sub>(PO<sub>4</sub>)<sub>3</sub>O<sub>12</sub>F<sub>2</sub>] (<bold>2</bold>) contain uranyl phosphate layers exhibiting a new sheet topology that can be related to that of β-U<sub>3</sub>O<sub>8</sub>, while Cs<sub>4.4</sub>K<sub>0.6</sub>[(UO<sub>2</sub>)<sub>6</sub>O<sub>4</sub>F(PO<sub>4</sub>)<sub>4</sub>(UO<sub>2</sub>)] (<bold>3</bold>) and Rb<sub>4.4</sub>K<sub>0.6</sub>[(UO<sub>2</sub>)<sub>6</sub>O<sub>4</sub>F(PO<sub>4</sub>)<sub>4</sub>(UO<sub>2</sub>)] (<bold>4</bold>) contain layers of a known isomer of the prominent phosphuranylite topology. The location of the fluorine in structures <bold>2</bold>-<bold>4</bold> is discussed using bond valence sums. First principles calculations were used to explore why a pure oxide structure is obtained for the Cs containing phase (<bold>1</bold>) and in contrast an oxyfluoride phase for the Rb containing phase (<bold>2</bold>). Ion exchange experiments were performed on <bold>1</bold> and <bold>2</bold> and demonstrate the ability of these structures to exchange approximately half of the parent alkali cation with a target alkali cation in an aqueous concentrated salt solution. Optical measurements were performed on <bold>1</bold> and <bold>2</bold> and the UV-vis and fluorescence spectra show features characteristic of the <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>UO</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> uranyl group.</p>