Wan-Sheng You

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 .

Polarized micropores in a novel 3D metal-organic framework for selective adsorption properties.

A novel 3D porous metal-organic framework with 1D polarized channels was synthesized, and its adsorption properties for gas separation and chemical sensing were studied. The framework shows a preferential adsorption of CO(2) over N(2) with a selectivity of 22:1. It also exhibits a very good sensitivity to water with respect to most of the organic solvents in view of chemical sensing applications.

Two New Armtype Polyoxometalates Grafted on Titanium Dioxide Films: Towards Enhanced Photoelectrochemical Performance.

Two new carboxyethyltin-functionalized polyoxometalates (POMs) were successfully obtained and confirmed with physicochemical and spectroscopic methods including X-ray crystallography. The lowest unoccupied molecular orbitals of both compounds are higher in energy than that of TiO2 , and the optical band gaps of these compounds are smaller than that of TiO2 . Grafting them onto a TiO2 film created two kinds of novel photoanode materials that showed significantly enhanced photovoltaic and photocurrent responses, as well as improved photoelectrooxidation activities for methanol relative to that shown by a single TiO2 film. Further, P2 W15 -Co-SnR produced the largest photocurrent by exploring the photoelectric activities of a series of carboxyethyltin POM derivatives. This work provides new insight into the photoelectrochemical functionalization of POM-based organic-inorganic hybrids.

Two Keggin sandwich-type tungstophosphates modified by open-chain carboxyethyltin groups and transition metals

Two new polyoxometalates containing [PW9O34]9− (abbreviated as PW9) subunits, carboxyltin groups and transition metal ions, namely K10[Mn2{Sn(CH2)2COO}2[(B-α-PW9O34)2]·14H2O (1) and Na8K2 [Zn2{Sn(CH2)2COO}2[(B-α-PW9O34)2]·13H2O (2), were successfully assembled in aqueous solutions by a routine synthetic method, and fully characterized. They represent the first single crystal examples of open-chain carboxyethyltin group-modified Keggin sandwich-type tungstophosphates. Their important structural features are two open-chain carboxyethyltin moieties attached on the PW9 dimer, forming arm-type polyoxometalates. Furthermore, the fluorescence properties, electrocatalytic and oxidation catalytic activities were evaluated. More interestingly, the fluorescence quenching of 1/2-doped TiO2 was clearly observed, which means that the two compounds may be excellent components of photocatalytic materials.

Hydrothermal syntheses and crystal structures of crystalline catalysts based on 3-D Ln3+–pdc2− frameworks and [BW12O40]5− and their heterogeneous photocatalytic oxidation of thiophene

Five [BW12O40]5 − -containing metal-organic frameworks (MOFs), {K[Ln(H2O)4(pdc)]4}[BW12O40]·2H2O (Ln=La 1 and Ce 2, H2pdc = pyridine-2,6-dicarboxylate) and {K[Ln(H2O)3(pdc)]4}[BW12O40]·6H2O (Ln=Tb 3, Dy 4 and Er 5), are synthesized hydrothermally. Ln3+ and pdc2− are built into 3-D MOF segments containing large channels and cavities which are occupied by [BW12O40]5 − . Herein, we report MOF-containing polyoxometalates (POMs) as photocatalysts to oxidize thiophene with O2 as the oxidant. Photo-excited state species ([BW12O40]5−∗) are generated under UV irradiation and then H2O is oxidized into OH˙ radicals and O2 is reduced into O2 2−. The active oxygen species (O2 2−, OH˙) oxidize thiophene in the presence of photocatalysts and SO3, CO2, and H2O are obtained as photoproducts. ESR measurements provide evidence that OH˙ species are generated during photocatalysis.

Synthesis, spectroscopic properties and crystal structure of organophosphoryl polyoxotungstate α-[Bu4N]3H[PhCH2P(O)]2SiW11O39

Reaction of the monovacant heteropolyanions α-[SiW11O39]8− with PhCH2PO(OH)2 leads to the formation of the organophosphoryl derivative α-[Bu4N]3H[PhCH2P(O)]2SiW11O39 (1). Single-crystal X-ray diffraction analysis shows that the crystal is monoclinic with space group P21 /n and the unit cell parameters: a = 14.386 (3) Å, b = 27.015 (5) Å, c = 25.480 (5) Å, α = 90°, β = 91.44 (3)°, γ = 90°, V = 9899 (3) Å3. Z = 4, D c = 2.467 g cm−1, λ (Mo-Kα) = 0.071073 nm, R 1 = 0.0638, wR 2 = 0.1364. The hybrid anion consists of an α-[SiW11O39]8− framework on which two equivalent organophosphoryl groups are grafted through P−O−W bridges; each of the two PhCH2P(O) groups are connected to two terminal oxygen atoms belonging to a triad and a diad, respectively.

Synthesis and spectroscopic characterization of organophosphoryl tungstosilicates α - [RP(O)] 2 SiW 11 O 39 4−

Abstract A series of organophosphoryl tungstosilicates α-[RP(O)]2SiW11O394− have been synthesized and characterized by elemental analysis, IR, 31 P and 183 W NMR. According to the elemental analysis and spectroscopic data, the hybrid anions consist of an α-[SiWn11O39] framework on which are grafted two equivalent organophosphoryl groups through P–O–W bridges.

Hydrothermal synthesis and crystal structures of two new divalent metal phosphonates with layered structure

Two divalent metal phosphonates with a layered structure, Zn(H2L) (1) and Cd2L (2) (H4L = CH3CH2CH2N(CH2PO3H2)2), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. The structure of 1 shows a layered structure in which the 1D zinc(II) phosphonate chains are interconnected by bridging organic groups to form 2D layers. In 2, the interconnection of [CdO5N] and [CdO5] polyhedra via edge-sharing forms a dimer. The dimers are interconected by [CPO3] tetrahedra via corner-sharing to form 2D double layers in the bc-plane.

Hydrothermal syntheses, crystal structures, and thermal stability of two new 3D open-framework metal(II) phosphonates

This article reports the hydrothermal synthesis and characterization of two new phosphonate compounds NaCo[O3PCH(OH)CO2] (1) and NaMn[O3PCH(OH)CO2] (2) based on 2-hydroxyphosphonoacetic acid (H3L). Their structures have been characterized by single-crystal X-ray diffraction as well as with elemental analysis, infrared spectroscopy and thermogravimetric analysis. The two isomorphous compounds crystalline in the orthorhombic, space group Pbca: Crystal data for 1: a = 10.1827(8) Å, b = 9.6673(8) Å, c = 10.7853(9) Å, V = 1061.70(15) Å3, Z = 8, R 1 = 0.0252, wR 2 = 0.0577; Crystal data for 2: a = 10.4309(18) Å, b = 9.7913(17) Å, c = 10.9012(19) Å, V = 1113.4(3) Å3, Z = 8, R 1 = 0.0194, wR 2 = 0.0536. In the two compounds, the metal atoms are octahedrally coordinated; all oxygen atoms from the H3L ligand are involved in coordination. The overall structures can be described as a 3D open framework with channels running along the a axis and the charge-compensating Na+ cations being located at the intersections of these channels.

Synthesis and characterization of organophosphoryl polyoxotungstates [RP(O)]2Xn+W11O39(8−n)− (Xn+ = P5+, Si4+, Ge4+, Ga3+)

In the presence of n-Bu4NBr acting as phase-transfer reagent, n-Bu4N+ salts of organophosphoryl polyoxotungstate derivatives [RP(O)]2Xn+W11O39(8−n)− [R = PhCH2CH2P(O), X = P, Si; R = C6H11P(O); X = Ge, Ga] have been prepared and characterized by elemental analysis, i.r., 31P- and 183W-n.m.r. spectroscopy. According to the elemental analysis and spectroscopic data, the hybrid anions consist of an α-[XW11O39] framework on which are grafted two equivalent organophosphoryl groups through P—O—W bridges; these new species still retain the Keggin structure. The six-line 183W spectrum indicates that hybrid anions possess Cs symmetry in MeCN.