4 research outputs found
Series of 2D Heterometallic Coordination Polymers Based on Ruthenium(III) Oxalate Building Units: Synthesis, Structure, and Catalytic and Magnetic Properties
A series of 2D ruthenium-based coordination
polymers with hcb-hexagonal
topology, {[KĀ(18-crown-6)]<sub>3</sub>[M<sup>II</sup><sub>3</sub>(H<sub>2</sub>O)<sub>4</sub>{RuĀ(ox)<sub>3</sub>}<sub>3</sub>]}<i><sub>n</sub></i> (M<sup>II</sup> = Mn (<b>1</b>), Fe (<b>2</b>), Co (<b>3</b>), Cu (<b>4</b>), Zn (<b>5</b>)), has been synthesized through self-assembly reaction. All compounds
are isostructural frameworks that crystallize in the monoclinic space
group <i>C</i>2/<i>c</i>. The crystal packing
consists of a 2D honeycomb-like anionic mixed-metal framework intercalated
by [KĀ(18-crown-6)]<sup>+</sup> cationic template. Dehydration processes
take place in the range 40ā200 Ā°C exhibiting two phase
transitions. However, the spontaneous rehydration occurs at room temperature.
Both hydrated and dehydrated compounds were tested as Lewis acids
heterogeneous catalysts in the acetalyzation of benzaldehyde achieving
high yields with the possibility to be recovered and reused. All the
investigated materials do not show any long-range magnetic ordering
down to 2 K. However, the Fe-based compound <b>2</b> presents
a magnetic irreversibility in the ZFC-FC magnetization data below
5 K, which suggest a spin-glass-like behavior, characterized also
by short-range ferromagnetic correlations. The coercive field increases
as the temperature is lowered below 5 K, reaching a value of 1 kOe
at 2 K. Alternating current measurements obtained at different frequencies
confirm the freezing process that shows weak frequency dependence,
being characteristic of a system exhibiting competing magnetic interactions
Series of Metal Organic Frameworks Assembled from Ln(III), Na(I), and Chiral Flexible-Achiral Rigid Dicarboxylates Exhibiting Tunable UVāvisāIR Light Emission
Two series of isoreticular chiral metalāorganic
frameworks
assembled from LnĀ(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), NaĀ(I),
and chiral flexible-achiral rigid dicarboxylate ligands, formulated
as [NaLnĀ(Tart)Ā(BDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S1</b>)
and [NaLnĀ(Tart)Ā(biBDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S2</b>) (H<sub>2</sub>Tart = tartaric acid; H<sub>2</sub>BDC = terephthalic
acid; H<sub>2</sub>biBDC = biphenyl-4,4ā²-dicarboxylic acid),
were obtained as single phases under hydrothermal conditions. The
compounds have been studied by single-crystal and powder X-ray diffraction,
thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR),
scanning electron microscopy (SEM-EDX), elemental analysis, and X-ray
thermodiffractometry. The catalytic activity has been also investigated.
The photoluminescence properties of selected compounds have been investigated,
exhibiting room temperature tunable UVāvisāIR light
emission
Series of Metal Organic Frameworks Assembled from Ln(III), Na(I), and Chiral Flexible-Achiral Rigid Dicarboxylates Exhibiting Tunable UVāvisāIR Light Emission
Two series of isoreticular chiral metalāorganic
frameworks
assembled from LnĀ(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), NaĀ(I),
and chiral flexible-achiral rigid dicarboxylate ligands, formulated
as [NaLnĀ(Tart)Ā(BDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S1</b>)
and [NaLnĀ(Tart)Ā(biBDC)Ā(H<sub>2</sub>O)<sub>2</sub>] (<b>S2</b>) (H<sub>2</sub>Tart = tartaric acid; H<sub>2</sub>BDC = terephthalic
acid; H<sub>2</sub>biBDC = biphenyl-4,4ā²-dicarboxylic acid),
were obtained as single phases under hydrothermal conditions. The
compounds have been studied by single-crystal and powder X-ray diffraction,
thermal analyses (TG-MS and DSC), vibrational spectroscopy (FTIR),
scanning electron microscopy (SEM-EDX), elemental analysis, and X-ray
thermodiffractometry. The catalytic activity has been also investigated.
The photoluminescence properties of selected compounds have been investigated,
exhibiting room temperature tunable UVāvisāIR light
emission
Consequences of Nitrogen Doping and Oxygen Enrichment on Titanium Local Order and Photocatalytic Performance of TiO<sub>2</sub> Anatase
Extended X-ray absorption
fine structure (EXAFS) investigation
of the oxygen-rich titania formed via the thermal treatment of N-doped
TiO<sub>2</sub> has revealed that the removal of N-dopants is responsible
for the creation of defect sites in the titanium environment, thus
triggering at high temperatures (500ā800 Ā°C) the capture
of atmospheric oxygen followed by its diffusion toward the vacant
sites and formation of interstitial oxygen species. The effect of
the dopants on Ti coordination number and TiāO<sub>int</sub> and TiāN<sub>int</sub> bond distances has been estimated.
The photocatalytic <i>p</i>-cresol degradation tests have
demonstrated that the interband states formed by the N-dopants contribute
to a greater extent to the visible-light activity than the oxygen
interstitials do. However, under the UV irradiation the oxygen-rich
titania shows higher efficiency in the pollutant degradation, while
the N-dopants in NāTiO<sub>2</sub> play the role of recombination
sites. The presence of the surface nitrogen species in TiO<sub>2</sub> is highly beneficial for the application in partial photooxidation
reactions, where NāTiO<sub>2</sub> demonstrates a superior
selectivity of 5-hydroxymethyl furfural (HMF) oxidation to 2,5-furandicarboxĀaldehyde
(FDC). Thus, this work underlines the importance of a rational design
of nonmetal doped titania for photocatalytic degradation and partial
oxidation applications, and it establishes the role of bulk defects
and surface dopants on the TiO<sub>2</sub> photooxidation performance