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, {[K­(18-crown-6)]₃[M^II₃(H₂O)₄{Ru­(ox)₃}₃]}<i>_n</i> (M^II = 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 [K­(18-crown-6)]⁺ cationic template. Dehydration processes take place in the range 40–200 °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 UV–vis–IR Light Emission

Two series of isoreticular chiral metal–organic frameworks assembled from Ln­(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), Na­(I), and chiral flexible-achiral rigid dicarboxylate ligands, formulated as [NaLn­(Tart)­(BDC)­(H₂O)₂] (<b>S1</b>) and [NaLn­(Tart)­(biBDC)­(H₂O)₂] (<b>S2</b>) (H₂Tart = tartaric acid; H₂BDC = terephthalic acid; H₂biBDC = biphenyl-4,4′-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 UV–vis–IR light emission

Series of Metal Organic Frameworks Assembled from Ln(III), Na(I), and Chiral Flexible-Achiral Rigid Dicarboxylates Exhibiting Tunable UV–vis–IR Light Emission

Two series of isoreticular chiral metal–organic frameworks assembled from Ln­(III) (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb), Na­(I), and chiral flexible-achiral rigid dicarboxylate ligands, formulated as [NaLn­(Tart)­(BDC)­(H₂O)₂] (<b>S1</b>) and [NaLn­(Tart)­(biBDC)­(H₂O)₂] (<b>S2</b>) (H₂Tart = tartaric acid; H₂BDC = terephthalic acid; H₂biBDC = biphenyl-4,4′-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 UV–vis–IR light emission

Consequences of Nitrogen Doping and Oxygen Enrichment on Titanium Local Order and Photocatalytic Performance of TiO₂ Anatase

Extended X-ray absorption fine structure (EXAFS) investigation of the oxygen-rich titania formed via the thermal treatment of N-doped TiO₂ 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 (500–800 °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 Ti–O_int and Ti–N_int 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 N–TiO₂ play the role of recombination sites. The presence of the surface nitrogen species in TiO₂ is highly beneficial for the application in partial photooxidation reactions, where N–TiO₂ demonstrates a superior selectivity of 5-hydroxymethyl furfural (HMF) oxidation to 2,5-furandicarbox­aldehyde (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 TiO₂ photooxidation performance