6 research outputs found
Multiple Fluorine-Substituted Phosphate Germanium Fluorides and Their Thermal Stabilities
Anhydrous compounds
are crucially important for many technological applications, such
as achieving high performance in lithium/sodium cells, but are often
challenging to synthesize under hydrothermal conditions. Herein we
report that a modified solvo-/hydro-fluorothermal method with fluoride-rich
and water-deficient condition is highly effective for synthesizing
anhydrous compounds by the replacement of hydroxyl groups and water
molecules with fluorine. Two anhydrous phosphate germanium fluorides,
namely, Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] and K<sub>4</sub>[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)], with chainlike
structures involving multiple fluorine substitutions, were synthesized
using the modified solvo-/hydro-fluorothermal method. The crystal
structure of Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] is constructed
by the common single chains <sub>ā</sub><sup>1</sup>{[GeF<sub>4</sub>(PO<sub>4</sub>)]<sup>3ā</sup>} built from alternating
GeO<sub>2</sub>F<sub>4</sub> octahedra and PO<sub>4</sub> tetrahedra.
For K<sub>4</sub>[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)], it
takes the same single chain in Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] as the backbone but has additional flanking GeOF<sub>5</sub> octahedra via an O-corner of the PO<sub>4</sub> groups, resulting
in a dendrite zigzag single chain <sub>ā</sub><sup>1</sup>{[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)]<sup>4ā</sup>}. The multiple
fluorine substitutions in these compounds not only force them to adopt
the low-dimensional structures because of the ātailor effectā
but also improve their thermal stabilities. The thermal behavior of
Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] was investigated by
an in situ powder X-ray diffraction experiment from room temperature
to 700 Ā°C. The modified solvo-/hydro-fluorothermal method is
also shown to be effective in producing the most germanium-rich compounds
in the germanophosphate system
Multiple Fluorine-Substituted Phosphate Germanium Fluorides and Their Thermal Stabilities
Anhydrous compounds
are crucially important for many technological applications, such
as achieving high performance in lithium/sodium cells, but are often
challenging to synthesize under hydrothermal conditions. Herein we
report that a modified solvo-/hydro-fluorothermal method with fluoride-rich
and water-deficient condition is highly effective for synthesizing
anhydrous compounds by the replacement of hydroxyl groups and water
molecules with fluorine. Two anhydrous phosphate germanium fluorides,
namely, Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] and K<sub>4</sub>[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)], with chainlike
structures involving multiple fluorine substitutions, were synthesized
using the modified solvo-/hydro-fluorothermal method. The crystal
structure of Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] is constructed
by the common single chains <sub>ā</sub><sup>1</sup>{[GeF<sub>4</sub>(PO<sub>4</sub>)]<sup>3ā</sup>} built from alternating
GeO<sub>2</sub>F<sub>4</sub> octahedra and PO<sub>4</sub> tetrahedra.
For K<sub>4</sub>[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)], it
takes the same single chain in Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] as the backbone but has additional flanking GeOF<sub>5</sub> octahedra via an O-corner of the PO<sub>4</sub> groups, resulting
in a dendrite zigzag single chain <sub>ā</sub><sup>1</sup>{[Ge<sub>2</sub>F<sub>9</sub>(PO<sub>4</sub>)]<sup>4ā</sup>}. The multiple
fluorine substitutions in these compounds not only force them to adopt
the low-dimensional structures because of the ātailor effectā
but also improve their thermal stabilities. The thermal behavior of
Na<sub>3</sub>[GeF<sub>4</sub>(PO<sub>4</sub>)] was investigated by
an in situ powder X-ray diffraction experiment from room temperature
to 700 Ā°C. The modified solvo-/hydro-fluorothermal method is
also shown to be effective in producing the most germanium-rich compounds
in the germanophosphate system
Dimensional Reduction From 2D Layer to 1D Band for Germanophosphates Induced by the āTailor Effectā of Fluoride
The ātailor effectā
of fluoride, exclusively as a terminal rather than a bridge, was applied
successfully to design low-dimensional structures in the system of
transition metal germanophosphates for the first time. Two series
of new compounds with low-dimensional structures are reported herein.
KĀ[<i>M</i><sup>II</sup>GeĀ(OH)<sub>2</sub>(H<sub>0.5</sub>PO<sub>4</sub>)<sub>2</sub>] (<i>M</i> = Fe, Co) possess
flat layered structures built from single chains of edge-sharing <i>M</i><sup>II</sup>O<sub>6</sub> and GeO<sub>6</sub> octahedra
interconnected by HPO<sub>4</sub> tetrahedra. Their fluorinated derivatives,
K<sub>4</sub>[<i>M</i><sup>II</sup>Ge<sub>2</sub>F<sub>2</sub>(OH)<sub>2</sub>Ā(PO<sub>4</sub>)<sub>2</sub>(HPO<sub>4</sub>)<sub>2</sub>]Ā·2H<sub>2</sub>O (M = Fe, Co), exhibit band structures
of two four-membered ring germanium phosphate single chains sandwiched
by M<sup>II</sup>O<sub>6</sub> octahedra via corner-sharing. Both
of these structures contain anionic chains of the condensation of
four-membered rings built from alternating GeO<sub>4</sub>Ī¦<sub>2</sub> (Ī¦ = F, OH) octahedra and PO<sub>4</sub> tetrahedra
via sharing common GeO<sub>4</sub>Ī¦<sub>2</sub> (Ī¦ = F,
OH) octahedra, the topology of which is the same as that of the mineral
kroĢhnkite [Na<sub>2</sub>CuĀ(SO<sub>4</sub>)<sub>2</sub>Ā·2H<sub>2</sub>O]. Note that the switch from the two-dimensional layered
structure to the one-dimensional band structure was performed simply
by the addition of a small amount of KFĀ·2H<sub>2</sub>O to the
reaction mixture. This structural alteration arises from the incorporation
of one terminal F atom to the coordination sphere of Ge, which breaks
the linkage between the transition metal and germanium octahedra in
the layer to form the band structure
Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder
Structural assembly from phosphate
to germanophosphate by applying germanate as a binder has been achieved.
Two isotypic porous compounds, K<sub>3</sub>[M<sup>II</sup><sub>4</sub>(HPO<sub>4</sub>)<sub>2</sub>]Ā[Ge<sub>2</sub>OĀ(OH)Ā(PO<sub>4</sub>)<sub>4</sub>]Ā·<i>x</i>H<sub>2</sub>O (<i>M</i><sup>II</sup> = Fe, Cd; <i>x</i> = 2 for Fe and 3 for Cd,
denoted as <b>KFeGePO-1</b> and <b>KCdGePO-1</b>, respectively),
contain a known transition-metal phosphate (TMPO) layer, <sub>ā</sub><sup>2</sup>{[<i>M</i><sub>2</sub>(HPO<sub>4</sub>)<sub>3</sub>]<sup>2ā</sup>}, which is built from chains of trans-edge-sharing <i>M</i>O<sub>6</sub> octahedra bridged by <i>M</i>O<sub>5</sub> trigonal bipyramids that were further linked and decorated by phosphate
tetrahedra. The layers are bound by infinite chains of GeO<sub>5</sub>(OH) octahedra, resulting in a 3D open-framework structure with 1D
12-ring channels that are occupied by K<sup>+</sup> ions and water
molecules. The curvature of the TMPO layers and shape of the 12-ring
windows can be tuned by the transition metals because of their JahnāTeller
effect
Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder
Structural assembly from phosphate
to germanophosphate by applying germanate as a binder has been achieved.
Two isotypic porous compounds, K<sub>3</sub>[M<sup>II</sup><sub>4</sub>(HPO<sub>4</sub>)<sub>2</sub>]Ā[Ge<sub>2</sub>OĀ(OH)Ā(PO<sub>4</sub>)<sub>4</sub>]Ā·<i>x</i>H<sub>2</sub>O (<i>M</i><sup>II</sup> = Fe, Cd; <i>x</i> = 2 for Fe and 3 for Cd,
denoted as <b>KFeGePO-1</b> and <b>KCdGePO-1</b>, respectively),
contain a known transition-metal phosphate (TMPO) layer, <sub>ā</sub><sup>2</sup>{[<i>M</i><sub>2</sub>(HPO<sub>4</sub>)<sub>3</sub>]<sup>2ā</sup>}, which is built from chains of trans-edge-sharing <i>M</i>O<sub>6</sub> octahedra bridged by <i>M</i>O<sub>5</sub> trigonal bipyramids that were further linked and decorated by phosphate
tetrahedra. The layers are bound by infinite chains of GeO<sub>5</sub>(OH) octahedra, resulting in a 3D open-framework structure with 1D
12-ring channels that are occupied by K<sup>+</sup> ions and water
molecules. The curvature of the TMPO layers and shape of the 12-ring
windows can be tuned by the transition metals because of their JahnāTeller
effect
Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder
Structural assembly from phosphate
to germanophosphate by applying germanate as a binder has been achieved.
Two isotypic porous compounds, K<sub>3</sub>[M<sup>II</sup><sub>4</sub>(HPO<sub>4</sub>)<sub>2</sub>]Ā[Ge<sub>2</sub>OĀ(OH)Ā(PO<sub>4</sub>)<sub>4</sub>]Ā·<i>x</i>H<sub>2</sub>O (<i>M</i><sup>II</sup> = Fe, Cd; <i>x</i> = 2 for Fe and 3 for Cd,
denoted as <b>KFeGePO-1</b> and <b>KCdGePO-1</b>, respectively),
contain a known transition-metal phosphate (TMPO) layer, <sub>ā</sub><sup>2</sup>{[<i>M</i><sub>2</sub>(HPO<sub>4</sub>)<sub>3</sub>]<sup>2ā</sup>}, which is built from chains of trans-edge-sharing <i>M</i>O<sub>6</sub> octahedra bridged by <i>M</i>O<sub>5</sub> trigonal bipyramids that were further linked and decorated by phosphate
tetrahedra. The layers are bound by infinite chains of GeO<sub>5</sub>(OH) octahedra, resulting in a 3D open-framework structure with 1D
12-ring channels that are occupied by K<sup>+</sup> ions and water
molecules. The curvature of the TMPO layers and shape of the 12-ring
windows can be tuned by the transition metals because of their JahnāTeller
effect