Zhen-Gang Sun

Synthesis, crystal structures and luminescence properties of lanthanide oxalatophosphonates with a three-dimensional framework structure

Six new three-dimensional (3D) lanthanide oxalatophosphonates, [Ln(HL)(C2O4)0.5(H2O)2]·H2O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6); H3L = H2O3PCH(OH)CO2H), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction as well as by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Compounds 1–6 are isomorphous and they exhibit a complex three-dimensional (3D) open-framework structure with a one-dimensional channel system along the c-axis. The interconnection of the lanthanide(III) ions by phosphonate ligands results in a lanthanide phosphonate layer, and these layers are further bridged by oxalate anions to form a 3D open-framework. Compound 6 shows strong red luminescence in the solid state at room temperature.

Synthesis, structure, surface photovoltage and magnetic properties of a novel 3D homochiral manganese phosphonate with right-handed helical chains

A novel 3D homochiral manganese phosphonate with right-handed helical chains, [enH2]0.5Mn2[(HL)(L)] (1) (H3L = 2-hydroxyphosphonoacetic acid; en = ethylenediamine) has been synthesized by hydrothermal techniques. X-Ray diffraction analysis indicates that compound 1 consists of A channels with right-handed single helical chains, B channels with right-handed double helical chains and C channels with achiral channels that are connected through manganese centers and L3− ligands to form a homochiral coordination polymer. Surface photovoltage spectroscopy (SPS) of compound 1 indicates that it possesses positive SPV response in the range of 300–600 nm and shows p-type semiconductor characteristic. Magnetic susceptibility studies of compounds 1 reveal that there exist weak antiferromagnetic interactions between the manganese centers.

Effect of Nd3+ doping on photocatalytic activity of TiO2 nanoparticles for water decomposition to hydrogen

Abstract The undoped TiO 2 and Nd 3+ -doped TiO 2 samples were prepared by the sol–gel method and characterized by X-ray diffraction, diffuse reflectance UV-visible spectroscopy, transmission electron microscopy, and N 2 adsorption. The correlation of the photocatalytic activity for hydrogen evolution with the phase composition, BET surface area, and light absorption intensity in the UV region was investigated. For the undoped TiO 2 sample, the particle size and agglomeration increased while the BET surface area and the light absorption intensity in the UV region decreased with increasing calcination temperature. The anatase to rutile phase transformation started at 600°C and completed at 800°C. The photocatalytic activity of undoped TiO 2 decreased with increasing calcination temperature, and the sample calcined at 600°C was the best because of the coexistence of a certain proportion of rutile/anatase mixed phase. For the Nd 3+ /TiO 2 samples, Nd 3+ doping inhibited the crystal phase transformation and the rutile phase appeared at 800°C. Moreover, Nd 3+ doping restrained the growth of grain size, improved the dispersivity of the particles, and raised BET surface area. The more the doping amount, the larger the BET surface area. As the calcination temperature increased, the decreasing extent of the light absorption intensity of Nd 3+ /TiO 2 in the UV region was lower than that of undoped TiO 2 . Nd 3+ doping raised the photocatalytic activity for hydrogen generation, and the optimum amount of Nd 3+ doping was 0.1%, at which the photocatalytic activity of Nd 3+ /TiO 2 was 3.5 times that of undoped TiO 2 .

Synthesis, crystal structures, and surface photovoltage properties of four new metal diphosphonates based on the mixed ligands

By introduction of 2,2′-bipy or 1,10-phen as a second organic ligand, four new metal diphosphonates with mixed ligands, namely, [M(2,2′-bipy)(hedpH3)2]·H2O (M = Co (1), Ni (2)), [M(1,10-phen)(hedpH3)2]·H2O (M = Co (3), Ni (4)) (hedpH4 = 1-hydroxyethylidenediphosphonic acid, 2,2′-bipy = 2,2′-bipyridine, 1,10-phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions. Compounds 1 and 2 are isostructural and adopt a 2D supramolecular network. Each {MN2O4} octahedron and four {CPO3} tetrahedra are interconnected into a {M(2,2′-bipy)(hedpH3)2} (M = Co (1), Ni (2)) unit via corner-sharing. These isolated units are interlinked through hydrogen bonding interactions to form 1D infinite chains, which are further assembled into a 2D supramolecular network through π–π stacking interactions. Compounds 3 and 4 are also isostructural and show a 1D double chain structure constructed from {M(1,10-phen)(hedpH3)2} (M = Co (3), Ni (4)) units. In compounds 3 and 4, the {M(1,10-phen)(hedpH3)2} units are linked to each other through hydrogen bonds to form a 1D infinite chain and then these 1D chains are further extended into 1D double chains by π–π stacking interactions. The surface photovoltage properties of compounds 1–4 have been investigated.

Synthesis, characterization, and MTO performance of MeAPSO-34 molecular sieves

MeAPSO-34 molecular sieves were synthesized successfully with metal ions of Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Ca, Sr, and Ba (Me/Al2O3=0.05). IR, NH3-TPD measurements and fixed bed MTO performances of all the samples were carried out in comparison with SAPO-34. The results illustrated that the incorporation of metal ions had great effects on structure and acidity of the molecular sieves. It was interesting that most MeAPSO-34 molecular sieves exhibited effective enhancement of the MTO performance. Especially, the incorporation of Co2+, Zn2+ and Mg2+ ions showed promising modification effect for the MTO catalysts.

Syntheses, structures, luminescence and molecular recognition properties of four new cadmium carboxyphosphonates with 2D layered and 3D supramolecular structures

Four new cadmium carboxyphosphonates with 2D layered and 3D supramolecular structures, namely, Cd3[(4-cppH)2(4-cppH2)2] (1), Cd[(2,2′-bipy)(4-cppH)] (2), [Cd3(1,10-phen)3(4-cpp)2]·6H2O (3) and [Cd(4,4′-bipy)(4-cppH)(H2O)2]·2H2O (4) (4-cppH3 = 4-carboxyphenylphosphonic acid, 2,2′-bipy = 2,2′-bipyridine, 1,10-phen = 1,10-phenanthroline and 4,4′-bipy = 4,4′-bipyridine), were synthesized under hydrothermal conditions. In compound 1, {Cd(1)O6}, {Cd(2)O6}, {Cd(3)O6} and {CPO3} polyhedra form a layer in the ab plane via edge- and corner-sharing. Neighboring layers assemble into a 3D supramolecular network by hydrogen bonding interactions. The structure of compound 2 shows a new layered structure, in which the interconnection of two {Cd(1)O4N2} and two {CPO3} polyhedra via corner-sharing forms a tetranuclear cluster, and the so-built tetranuclear clusters are bridged by phosphonate ligands into a 2D layer. For compound 3, {Cd(1)O4N2}, {Cd(2)O4N2}, {Cd(3)O3N2} and {CPO3} polyhedra are interconnected by carboxyphosphonate ligands to a 2D layer in the ac plane. Then the adjacent layers are further assembled into a 3D supramolecular structure through π–π stacking interactions. Cd(II) ions in compound 4 are bridged by 4,4′-bipy molecules into layers in the ab plane. These layers are held together by hydrogen bonds into a 3D supramolecular structure. The thermal stabilities and luminescence properties of compounds 1–4 were investigated. Interestingly, compound 1 is selective and reversible for sensing of DMF and acetone.

Mixed-solvothermal synthesis, structures, luminescent and surface photovoltage properties of four new transition metal diphosphonates with a 3D supramolecular structure

Four new transition metal(II) diphosphonates with a 3D supramolecular structure, M(hedpH2)3·3NH2(CH3)2NH(CH3)3·3H2O (M = Mn (1), Co (2), Ni (3), Zn (4); hedpH4 = 1-hydroxyethylidenediphosphonate acid) have been synthesized under mixed-solvothermal conditions and structurally characterized. Compounds 1–4 are isomorphous and adopt a three-dimensional supramolecular network structure containing {M(hedpH2)3}4− cluster units. The interconnection of {MO6} and {CPO3} polyhedra via corner-sharing forms a {M(hedpH2)3}4− cluster, and these isolated clusters are extended by hydrogen bonds to form a two-dimensional layer structure, which are further connected through hydrogen bonding interactions to give rise to a 3D supramolecular structure. Surface photovoltage spectroscopy (SPS) of compounds 1–4 indicates that it possesses positive SPV response in the range of 300–600 nm and shows p-type semiconductor characteristic. Luminescence properties of the four compounds have also been studied.

Synthesis, crystal structure and luminescence properties of eight new lanthanide carboxyphosphonates with a 3D framework structure

By using the carboxyphosphonic acid as the ligand, eight new three-dimensional (3D) lanthanide carboxyphosphonates, namely Ln[L(H2O)2]·2H2O (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Y (7), Tb (8); H3L = H2O3PCH2–NC5H9–COOH) have been synthesized under hydrothermal conditions and structurally characterized by X-ray single-crystal diffraction, X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. The eight isomorphous compounds feature a 3D framework structure. In these compounds, the inorganic chains based on LnO8 and CPO3 polyhedra are interconnected through carboxyphosphonate ligands to form a 3D framework structure with a channel system. The result of connections in this manner is the formation of 40- and 24-atom rings that run in the a- and b-axis directions. The luminescence properties of compounds 5 and 8 have also been studied.

Two fluorescent lead phosphonates for highly selective sensing of nitroaromatics (NACs), Fe3+ and MnO4− ions

Two novel lead(II) phosphonates with a 2D double-layer and a 3D framework structure, namely, [Pb(BPDP)] (1) and [Pb3(BPDP)1.5(OOCC6H4COOH)3] (2) (H2BPDP = 4,4′-biphenyldiphosphonate(monoethyl ester), H2bdc = HOOCC6H4COOH), have been synthesized under hydrothermal conditions. Compounds 1 and 2 are stable in air and insoluble in water. Thermogravimetric analyses reveal that compounds 1 and 2 remain unchanged up to about 233 °C and 212 °C, respectively. Luminescence explorations demonstrated that compounds 1 and 2 exhibit highly selective and sensitive sensing for nitroaromatics (NACs). In ion recognition, the choice of solvent for compounds 1 and 2 has a different effect. Experiments proved that the identification of compounds 1 and 2 in aqueous solution is superior to that in ethanol solution. Moreover, compounds 1 and 2 also exhibit highly selective and sensitive sensing for Fe3+ and MnO4−. These results reveal that compounds 1 and 2 may be excellent fluorescent sensors for p-NP, Fe3+, and MnO4−.

Syntheses, crystal structures, surface photovoltage, luminescence and molecular recognition properties of zinc(II) and iron(II) carboxyphosphonates with 2D and 3D supramolecular structures

Four new transition metal carboxyphosphonates with 2D and 3D supramolecular structures, namely, Fe2[(HL)(H2O)] (1), Fe(H4L)2 (2), Zn(H3L) (3) and Zn2(HL) (4) (H5L = 4-HO2C–C6H4–CH2N(CH2PO3H2)2), have been synthesized under hydrothermal conditions. For compound 1, {FeO5N} and {CPO3} polyhedra are interconnected into a 2D layer in the bc-plane via corner-sharing. Then the adjacent layers are further assembled into a 3D supramolecular structure through π–π stacking interactions. Compound 2 shows a 3D supramolecular structure. {FeO6} and {CPO3} polyhedra are interconnected into a 2D layer in the bc-plane via corner-sharing, which is further linked through π–π stacking interactions to form a 3D supramolecular structure. The overall structure of compound 3 can be described as a 2D supramolecular structure. The {ZnO4} polyhedra are interconnected by {CPO3} tetrahedra via corner-sharing to form a 1D chain. These neighboring metal phosphonate chains are connected through hydrogen bonding interactions to give rise to a 2D supramolecular structure in the ac-plane. In compound 4, {ZnO3N} and {ZnO4} polyhedra are interconnected by {CPO3} tetrahedra via corner-sharing and edge-sharing to form a 2D inorganic layer in the bc-plane, which is further linked through π–π stacking interactions to form a 3D supramolecular structure. The surface photovoltage properties of compounds 1–2 and luminescence properties of compounds 3–4 have been investigated. More interestingly, compound 4 is selective for sensing DMF and acetone.