Preparation of paramagnetic ferroferric oxide-calcined layered double hydroxide core-shell adsorbent for selective removal of anionic pollutants.

Adsorption is one of the most common methods of pollution treatment. The selectivity for pollutants and recyclability of adsorbents are crucial to reduce the treatment cost. Layered double hydroxide (LDH) materials are one type of adsorbent with poor recyclability. Prussian blue (PB) is a sturdy and inexpensive metal-organic framework material that can be used as the precursor for synthesizing paramagnetic ferroferric oxide (Fe3O4). It is intriguing to build some reusable adsorbents with magnetic separation by integrating LDH and PB. In this work, paramagnetic Fe3O4-calcined LDH (Fe3O4@cLDH) core-shell adsorbent was designed and prepared by the calcination of PB-ZnAl layered double hydroxide (PB@LDH) core-shell precursor, which exhibits high anionic dyes selectivity in wastewater solutions. The paramagnetism and adsorption capability of Fe3O4@cLDH come from the Fe3O4 core and calcined ZnAl-LDH shell, respectively. Fe3O4@cLDH shows an adsorption capacity of 230 mg g-1 for acid orange and a high selectivity for anionic dyes in cation-anion mixed dye solutions. The regeneration process indicates that the high selectivity for anions is related to the specific hydration recovery process of ZnAl-LDH. The synergistic effect of the paramagnetic Fe3O4 core and calcined ZnAl-LDH shell makes Fe3O4@cLDH an excellent magnetic separation adsorbent with high selectivity to anions.

Three Si-substituted polyoxovanadates as efficient catalysts for Knoevenagel condensation and selective oxidation of styrene to benzaldehyde.

Three new Si-substituted polyoxovanadates (POVs), [Cd2(dien)2][Cd(dien)][Cd(Hdien)2][V15Si6O46(OH)2(H2O)]·7H2O (1), [Co(enMe)2]3[Co2(enMe)2(H2O)2][V16Si4O44(OH)2(H2O)]·6H2O (2), and [Co(teta)]4[V16Si4O42(OH)4(H2O)]·10H2O (3) (dien = diethylenetriamine; enMe = 1,2-diaminopropane; teta = triethylenetetramine) were synthesized by the hydrothermal method and characterized. Structural analysis sheds light on the fact that the {V15Si6O48}/{V16Si4O46} clusters of compounds 1-3 were formed by replacing {VO5} square pyramids in the classical {V18O42} cluster with {Si2O7} units. Compound 1 is a 2D bilayer structure formed by the [V15Si6O46(OH)2(H2O)]10- cluster and two types of bridging Cd complexes containing binuclear groups [Cd2(dien)2]4+. Compound 2 is a 3D framework constructed from the [V16Si4O44(OH)2(H2O)]10- cluster and two types of Co complex fragments including binuclear [Co2(enMe)2(H2O)2]4+. In compound 3, the [V16Si4O42(OH)4(H2O)]8- cluster is connected with bridging [Co(teta)]2+ to expand into a 2D network. Compounds 1 and 3 represent the first 2D assemblies based on a vanadosilicate cluster. 1-3 served as heterogeneous catalysts and exhibited highly efficient catalytic activities for the Knoevenagel condensation under mild ambient conditions with low catalyst loading, featuring the open Lewis base {V15Si6O48}/{V16Si4O46} sites and Lewis acid Cd2+/Co2+ sites. The conversion of benzaldehyde was up to 99.3% in 80 min at room temperature using 1 as a heterogeneous catalyst with only 0.37% catalyst loading. Moreover, compounds 1-3 as catalysts for selective oxidation of styrene to benzaldehyde exhibited excellent catalytic performance, high selectivity and could be readily recycled. Most strikingly, compound 1 showed excellent catalytic performance with 97.6% conversion of styrene and 100% selectivity of benzaldehyde in 15 min. In addition, the catalytic activity of catalyst 1 was well maintained after five cycling reactions.

Preparation of LDO@TiO2 core-shell nanosheets for enhanced photocatalytic degradation of organic pollution.

TiO2-based nanosheet materials with a core-shell structure are expected to be one of the promising photocatalysts for the degradation of organic pollution. It is a challenge to synthesize TiO2 by the desired nucleation and growth process, so most reported TiO2 core-shell photocatalysts are prepared using TiO2 as a core material. Layered double hydroxides (LDHs) are considered ideal platforms to grow TiO2in situ and further serve as additional components to improve the separation of photogenerated charge carriers. In this work, we report the design and fabrication of anatase TiO2-coated ZnAl-layered double oxide (LDO@TiO2) nanosheets, which involve the in situ growth of TiO2 on ZnAl-LDH followed by subsequent calcination treatment. The resulting LDO@TiO2 photocatalyst yields typical core-shell nanosheet morphology with a mesoporous structure, exhibiting excellent photodegradation and mineralization efficiency for organic pollution.

The effect of the photochemical environment on photoanodes for photoelectrochemical water splitting.

Besides photoelectrode materials, realizing the synergy of the photochemical environment and photoelectrodes for high charge carrier utilization is crucial for enhancing the performance of photoelectrochemical (PEC) water splitting systems. However, few researchers have focused on this important aspect. Herein, the effect of the photochemical environment on photoanodes in PEC water splitting, including the redox potential of electrolytes and light direction, is rationally discussed. A combined study of the potential distribution and electrochemical impedance spectroscopy reveals that the low redox potential of electrolytes facilitates the interior charge transfer and surface charge utilization by enlarging the depletion layer. In addition, it is found that the optimum thickness of semiconductors in photoelectrodes is the length of the depletion layer plus diffusion layer.

A Bicadmium-Substituted Polyoxometalate Network Based on a Vanadosilicate Cluster for the Selective Oxidation of Styrene to Benzaldehyde.

A new bicadmium-substituted vanadosilicate, [Cd(en)2]2[(en)2Cd2Si8V12O40(OH)8(H2O)0.5]·5H2O (1; en = ethylenediamine), had been hydrothermally synthesized and characterized. Structural analysis revealed that the kind of new [(en)2Cd2Si8V12O40(OH)8(H2O)0.5]4- polyoxoanionic cluster was derived from the classical {V18O42} cluster by replacing six {VO5} square pyramids with four {Si2O7} and two [Cd(en)]2+ groups. Notably, such mixed substitution of both main-group and transition metals in polyoxovanadates is much less developed. Furthermore, compound 1 displays efficient catalytic activity toward the selective oxidation of styrene to benzaldehyde with a conversion of 97% and a selectivity of 87% in 8 h.

Impact of oxygen vacancies on TiO2 charge carrier transfer for photoelectrochemical water splitting.

Oxygen vacancies are recognized as the most prevalent defects in oxide materials. The effect of oxygen vacancies on the physicochemical properties of metal oxide semiconductors has attracted considerable attention in the photocatalysis field. But so far, the impact of oxygen vacancies on charge carrier transfer for photoelectrochemical water splitting has been unclear. In this work, TiO2 photoanodes with various oxygen vacancy concentrations were studied as metal oxide models to clarify the impact of oxygen vacancies on charge carrier transfer behaviors. The potential distribution and electrochemical impedance spectroscopy results indicate that the oxygen vacancies facilitate charge carrier diffusion in TiO2, but are disadvantageous for the charge carrier drift in the TiO2/electrolyte interface. The TiO2-400 photoanode with intermediate oxygen vacancy concentration exhibits the highest photocurrent density. It is expected that this work will provide reference to design and fabricate oxide semiconductors as photoanodes for higher charge carrier utilization in the field of solar-to-chemical energy conversion.

Reduced Phosphomolybdate Hybrids as Efficient Visible-Light Photocatalysts for Cr(VI) Reduction.

Photocatalytic reduction of hexavalent chromium [Cr(VI)] is a promising technology approach to highly efficiently and environmentally tackle the problem of Cr(VI) pollution, in which the key challenge is in the development of effective photocatalysts. In this work, highly reduced hourglass-type molybdophosphate hybrids with the formulas [Zn(mbpy)(H2O)2]2[Zn(mbpy)(H2O)]2{Zn[P4Mo6O31H7]2}·9H2O (1), [Na(H2O)2]2[Zn(mbpy)(H2O)]2[Zn(mbpy)(H2O)2]2{Zn[P4Mo6O31H6]2}·15H2O (2), and (H2mbpy){[Zn(mbpy)(H2O)]2[Zn(H2O)]2}{Zn[P4Mo6O31H6]2}·10H2O (3) (mbpy = 4,4'-dimethyl-2,2'-bipyridine) have been hydrothermally synthesized and used as photocatalysts for the reduction of Cr(VI) under mild conditions. Structural analysis showed that the inorganic moieties in crystals 1-3 are composed of a unique 0D single cluster form, a 1D chainlike structure, and a 2D-layered structure, respectively, in which polyanions were constructed by hourglass-type molybdophosphates with one Zn(II) ion as the central metal. These hybrids displayed good performance for the photocatalytic reduction of Cr(VI) by virtue of their wide visible-light adsorption, suitable energy band structures, and specific spatial arrangements of polyanionic species. Among them, hybrid 2 exhibits the best photocatalytic performance with a Cr(VI) reduction conversion rate of almost 94.7% within 180 min of reaction time. The photocatalysis mechanism investigation revealed that highly reduced hourglass-type molybdophosphate clusters can be illuminated by visible light. The photoinduced electrons induced by hourglass-type polyanions can directly reduce Cr(VI) to Cr(III), while the photogenerated holes are used to oxidize the sacrificial agent isopropyl alcohol to acetone. This work provides new guidance for the design and preparation of highly efficient photocatalysts for the reduction of Cr(VI).

Crystal structures of hybrid completely reduced phosphomolybdates and catalytic performance applied as molecular catalysts for the reduction of chromium(VI).

The exploration of highly efficient and low-cost catalysts for the treatment of hexavalent chromium CrVI in environmental remediation is currently one of the most challenging topics. Here, three phosphomolybdate hybrid compounds have been successfully isolated by the hydrothermal method and been applied as supramolecular catalysts for the reduction of CrVI. Single-crystal X-ray diffraction revealed their formulae as (H2bpp)2[Fe(H2O)][Sr(H2O)4]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·5H2O (1), (H2bpp)2[Na(H2O)(OC2H5)][Fe(H2O)2][Ca(H2O)2]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·4H2O (2) and (H2bpe)3{Fe[Mo6O12(OH)3(HPO4)3(H2PO4)]2}·8H2O (3) [bpp is 1,3-bis(pyridin-4-yl)propane (C13H14N2) and bpe is trans-1,2-bis(pyridin-4-yl)ethylene (C12H10N2)]. The three hybrids consist of supramolecular networks built up by noncovalent interactions between {Fe[P4Mo6VO31]2}22- polyanions and protonated organic cations. This kind of hybrid polyoxometalate could be applied as heterogeneous molecular catalysts for the reduction of CrVI. It was found that the organic moiety plays a vital role in influencing the catalytic activity of the polyanions. Organic bpp-containing hybrids 1 and 2 are highly active in the catalytic reduction of heavy metal CrVI ions using HCOOH as reductant, while bpe-containing hybrid 3 is inactive to this reaction. This work is significant for the design of new catalysts, as well as the exploration of reaction mechanisms at a molecular level.

Cu-based Polyoxometalate Catalyst for Efficient Catalytic Hydrogen Evolution.

Copper-based complexes have been largely neglected as potential water reduction catalysts. This article reports the synthesis and characterization of a tetra-copper-containing polyoxotungstate, Na3K7[Cu4(H2O)2(B-α-PW9O34)2]·30H2O (Na3K7-Cu4P2). Cu4P2 is a water-compatible catalyst for efficient visible-light-driven hydrogen evolution when coupled to (4,4'-di-tert-butyl-2,2'-dipyridyl)-bis(2-phenylpyridine(1H))-iridium(III) hexafluorophosphate ([Ir(ppy)2(dtbbpy)][PF6]) as a light absorber and triethanolamine (TEOA) as sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of ∼1270 per Cu4P2 catalyst is obtained after 5 h of irradiation (light-emitting diode; λ = 455 nm; 20 mW); a photochemical quantum efficiency of as high as 15.9% is achieved. Both oxidative and reductive quenching pathways are observed by measuring the luminescence intensity of excited state [Ir(ppy)2(dtbbpy)](+*) in the presence of Cu4P2 or TEOA, respectively. Many stability studies (e.g., UV-vis absorption, FT-IR, dynamic light scattering, transmission electron microscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy) show that catalyst Cu4P2 undergoes slow decomposition under turnover conditions; however, both the starting Cu4P2 as well as its molecular decomposition products are the dominant catalytically active species for H2 evolution not Cu or CuOx particles. Considering the high abundance and low cost of copper, the present work provides considerations for the design and synthesis of efficient, molecular, water-compatible Cu-based water reduction catalysts.

Syntheses, Structural Characterization, and Catalytic Properties of Di- and Trinickel Polyoxometalates.

The syntheses, structural characterization, and catalytic properties of two different nickel-containing polyoxometalates (POMs) are presented. The dinickel-containing sandwich-type POM [Ni2(P2W15O56)2](20-) (Ni2) exhibits an unusual αααα geometry. The trinickel-containing Wells-Dawson POM [Ni3(OH)3(H2O)3P2W16O59](9-) (Ni3) shows a unique structure where the [α-P2W15O56](12-) ligand is capped by a triangular Ni3O13 unit and a WO6 octahedron. Ni3 shows a high catalytic activity for visible-light-driven hydrogen evolution, while the activity for Ni2 is minimal. An analysis of the structures of multinickel-containing POMs and their hydrogen evolution activity is given.

Synthesis of MnFe2O4@Mn-Co oxide core-shell nanoparticles and their excellent performance for heavy metal removal.

Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused.

An unprecedented polyoxometalate-based hybrid solid constructed from a neutral metal-organic macrocycle and Dawson polyoxotungstate anions.

The self-assembly procedure of a Dawson-type polyoxotungstate with pyridine-2,6-dicarboxylate (H2pdc) and copper(II) ions produces an exquisite supramolecular aggregation. In the structure, a neutral cucurbit[n]uril-like metal-organic macrocycle is formed of six copper centers and six pdc(2-) ligands, while a pair of Dawson-type polyoxotungstates are linked to the bottom and top portals of this macrocycle at the joint with the alkali metal ions. A control experiment was carried out to produce a different metalloligand-supported hybrid (instead of the metallomacrocycle) to verify the structure-directing role of Dawson polyanions in the title compound. In addition, the photoluminescent and magnetic properties of the hybrid solid have also been investigated.

Controlled solvothermal synthesis of novel organic functionalized polyoxovanadates.

Four novel organic functionalized polyoxovanadates are solvothermally synthesized by altering the reaction temperature and using different organoarsonic acids. These POVs are fully characterized and the phase transitions between different POVs structures are confirmed by X-ray diffraction analyses. Such a transition is temperature-dependent and thus controlled synthesis of new POVs can be achieved.

Cation-induced synthesis of new polyoxopalladates.

Seven polyoxopalladate compounds, [Pd(15)(SeO(3))(10)(µ(3)-O)(10)](10-), with Na(+) (1) and K(+) (2) as counterions, and Na(6)[M(II){Pd(12)(SeO(3))(8)(µ(4)-O)(8)}]·nH(2)O (M = Co (3), Zn (4), Ni (5), Cu (6), Mn (7); n = 7-9), have been prepared and characterized by SXRD, FT-IR, UV-vis, EA, TGA, and ESI-MS. These compounds comprise two distinct cluster configurations, {Pd(15)} and {M(II)Pd(12)}, which reveals the possibility of obtaining desired noble metal clusters with a certain nuclearity by using different cations as potential structural directing or template agents in synthesis. All compounds showed apparent absorptions in the visible light region, while 3 and 7 were found to show paramagnetic behavior typical of mononuclear Co(II) and Mn(II) complexes with zero-field splitting.

Two three-dimensional {V16Ge4}-based open frameworks stabilized by diverse types of Co(II)-amine bridges and magnetic properties.

Two novel three-dimensional (3D) extended vanadogermanate-based frameworks, [Co(pdn)(2)](3)[Co(2)(pdn)(4)][V(16)Ge(4)O(44)(OH)(2)(H(2)O)]·5H(2)O (1), [Co(2)(en)(3)][Co(en)(2)](2)[Co(en)(2)(H(2)O)][V(16)Ge(4)O(44)(OH)(2)(H(2)O)]·10.5H(2)O (2), (pdn = 1,2-propanediamine, en = ethylenediamine) have been synthesized under hydrothermal conditions via changing the organic amine. X-ray crystal structure analyses reveal that both frameworks are built of [V(16)Ge(4)O(44)(OH)(2)(H(2)O)](10-) anions and different Co-amine cations. They represent the first example of incorporating elemental Co into the extended vanadogermanate frameworks. Compound 1 shows a 3D framework with NaCl topology based on {V(16)Ge(4)} clusters as nodes, while compound 2 exhibits a 3D (4,6)-connected network with a Schläfli symbol of (4(6)·6(7)·8(2))(2)(4(2)·6(4)), which is found for the first time in polyoxovanadate chemistry. The diverse types of metal-organoamine subunits play critical roles in the formation on the final structures. Furthermore, variable temperature susceptibility measurements on compounds 1 and 2 demonstrate the presence of anticipated rare ferrimagnetic behavior.

Novel hexagonal {V=O}6-containing sandwich-type cluster accompanied by in situ carbon-carbon bond formation of organic cations.

Two novel sandwich-type polyanions containing hexagonal {V=O}(6) group (H(2)tpy)(Hbpe)(3)H[(VO)(6)(SbW(9)O(33))(2)]·2H(2)O (1) and (H(2)tcy)(6)(Hbpp)(6)H(4)[VW(12)O(40)][(VO)(6)(SbW(9)O(33))(2)](3)·30H(2)O (2) (tpy = 4-(2,3,4-tri(pyridin-4-yl)butyl)pyridine, bpe = 1,2-(4-pyridyl)ethene, tcy = 1,2,4,5-tetra(pyridin-4-yl)cyclohexanol, bpp = 1,3-bis-(4-pyridyl)propane), were reported. Both compounds are built upon the complex hydrogen bonding networks of C-H···O and N-H···O occurred among inorganic anions and organic cations. Unusual in situ organic reactions involving C-C coupling are also observed in 1 and 2 regardless of the rigid bpe or flexible bpp. Compound 2 represents a rare case in which nano-sized α-Keggin [VW(12)O(40)](4-) and sandwich-type [(VO)(6)(SbW(9)O(33))(2)](6-) anionic clusters are present in a common crystal framework.

Introducing organosilicone source into the synthetic system of polyoxovanadates: two novel {V15Si6O48}-based extended chains.

Two novel extended chains based on rare {V(IV)(15)Si(6)O(48)} have been prepared under hydrothermal conditions by introducing an organosilicone source into the synthetic system of the polyoxovanadates. Single-crystal X-ray diffraction analyses show that the neighboring {V(IV)(15)Si(6)O(48)} clusters are linked by a pair of V(V)O(2) fragments via the coordination bonds of (Si-)O-V-O(-Si) to give rise to a zig-zag chain in compound 1, which is the first example of V(iv,v) mixed valence states successfully synthesized in {V(15)Si(6)O(48)}-containing POMs. While in 2 the linkages are changed to [Co(pdn)(2)(H(2)O)](2+) (pdn = 1,3-propanediamine) cations instead of {V(V)O(2)} fragments, to generate another comparable 1-D infinite chain, which demonstrates the first organic-inorganic vanadosilicon hybrid linked by a second transition-metal complex. The possible hydrolysis mechanism of tetraethyl orthosilicate as the Si source is postulated to afford a feasible protocol to synthesize a new type of vanadosilicate cluster. The magnetic properties of the two compounds have also been investigated.

Transformation from [W6O19](2-) to [W6O22](8-) stabilized by Cu(II) complexation.

A rare [W6O22](8-) fragment has been first captured in aqueous solution of [W6O19](2-) by using a transition-metal complex and isolated as a new compound [Cu4(W6O22)(L1)2(H2O)2]·2H2O (1; L1 = 2-amino-4,6-bis(2-pyridyl)pyrimidine), indicating that [W6O19](2-) could also transform to [W6O22](8-) in aqueous solution besides the earlier proven ψ-metatungstates, [W10O32](4-), ß-[(H2)W12O40](6-) and [W7O24](6-).

[Synthesis and fluorescence characteristics of Eu-TB complexes with trimesic acid].

A series of mixed rare earth complexes Eu(1-x)Tb(x) (BTC) x nH2O(H3BTC=1,3,5-H3BTC, x = 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) were synthesized by the reaction of trivalent rare earth chlorides with trimesic acid. The contents of rare earth were mearsured by using EDTA titration method, the element analyses of C and H were performed by Vario EL elemental analyzer. Their infrared spectra were recorded by FTIR-8900 infrared spectrophotometer with KBr pellet, and the fluorescence spectra were recorded by using a Hitachi F-4500 fluorescence spectrophotometer at room temperature. These results show that these complexes Eu(1-x) Tb(x) (BTC) x nH2O can emit intense fluorescence from europium ion, the intensity of the fluorescence of the series complexes is greater in (5)D0-->7F(1,2), and both the positions ((5)D0-->7F(1,2)) show splitting emission peaks, but the peak positions of their emission spectra basically remain unchanged. These may be caused by the different coordinating pattern of the carboxylate groups. Additionally, the fluorescence intensity of europium ions was sensitized by terbium ions and that of terbium ions was quenched by europium ions. in these complexes. It was attributed to efficient energy transfer from the strongly absorbing ligand to the rather poorly absorbing lanthanide ion. and from Tb3+ to Eu3+. Moreover, the fluorescence emission of terbium ions increased markedly in these complexes.

Associations between the CYBA 242C/T and the MPO -463G/A polymorphisms, oxidative stress and cardiovascular disease in chronic kidney disease patients.

Genetic variations in the NADPH/MPO system in chronic kidney disease (CKD) patients might lead to altered activity of these enzymes, and thus to altered risk for oxidative stress (OS) and cardiovascular disease (CVD). We evaluated the impact of 242C/T CYBA and -463G/A MPO polymorphisms on OS and CVD mortality in stage 5 CKD patients starting dialysis. Two hundred and fifty-seven patients were genotyped using Pyrosequencing. Plasmalogen [dimethylacetal (DMA) 16/C16:0] was used as OS marker. CVD was assessed from patient history and clinical symptoms. Prevalence of CVD was higher (35%) in GG patients (MPO) compared to AG (26%) and AA (0%) patients (p < 0.01). Patients with CC genotype (CYBA) had lower levels of DMA 16/C16:0 (ratio 0.071 +/- 0.003) compared to TT patients (0.089 +/- 0.006; p < 0.05). These patients also had increased CVD mortality compared to CT and TT patients (chi(2) 2.19; p < 0.05). We conclude that genetic variations in the NADPH/MPO system are associated with OS, presence of CVD and CVD-related mortality in CKD patients.