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Polyoxovanadates (POVs), as an important subfamily of polyoxometalates (POMs), have been attracting continuous interest due to their rich structural chemistry and unusual properties that make them attractive for applications in catalysis, magnetism, optics and medicine. In parallel with the large number of crystal structures of isopolyoxovanadates reported in the literature, the incorporation of heteroatoms into polyoxovanadate frameworks towards the functional materials has received considerable attention. This mini-review summarizes the recent advances on polyoxovanadates, and particularly highlights achievements that are concerned with organic-functionalized, substituted polyoxovanadium and vanadoniobates. We present the synthetic methods, structural features and applications mainly in catalysis and magnetism. The challenges and prospects of these emerging polyoxovanadates are also discussed. [ABSTRACT FROM AUTHOR]

Two [V15M6(OH)6O42(Cl)]7- (M = Si for 1, Ge for 2) cluster anions with protonated amines as counterions have been synthesized under hydrothermal conditions and characterized by FT-IR, energy dispersive spectroscopy, XPS, powder X-ray diffraction, thermogravimetric analysis (TGA), elemental analysis, and single-crystal X-ray analyses. Both compounds consist of {V15M6O42(OH)6(Cl)} (M = Si for 1, Ge for 2), which are derived from {V18O42} by substitution of three {VO5} square pyramids with three {Si2O5(OH)2/Ge2O5(OH)2} units. It represents the first example of cage-like polyoxovanadates (POVs) containing three (Si/Ge)2O5(OH)2 units. There are extensive hydrogen bonding interactions between POVs and organoamines in 1 and 2. Compound 1 presents a close-packed layer aggregate, while 2 exhibits the packing of six-membered rings with a 1-D channel. Magnetism measurements demonstrate the presence of strong antiferromagnetic interaction between VIV centers in 1. [ABSTRACT FROM AUTHOR]

Abstract: Inorganic–organic hybrid frameworks, namely [Ce(H2O)3(pdc)]4[SiW12O40]·6H2O 1, [M(H2O)4(pdc)]4[SiW12O40]·2H2O (M=Ce for 2a, La for 2b, Nd for 2c; H2pdc=pyridine-2,6-dicarboxylic acid) were assembled through incorporation of Keggin-type heteropolyanion [SiW12O40]4− within the voids of lanthanides-pdc network as pillars or guests under hydrothermal condition. Single-crystal X-ray analyses of these crystals reveal that compound 1 presents 3D pillar-layered framework with the [SiW12O40]4− anions located on the square voids of the two-dimensional Ce-pdc bilayer. Compounds 2a–c are isostructural and constructed from 3D Ln-pdc-based metal-organic framework (MOF) incorporating noncoordinating guests Keggin structure [SiW12O40]4−. Solid-state properties of compounds 1 and 2a–c such as thermal stability and photoluminescence have been further investigated. [Copyright &y& Elsevier]

Abstract: Reaction of in situ generated 4-(6-(pyridin-4-yl)pyridin-3-yl)phenol (pph) from 5-(4-bromophenyl)-2-(pyridin-4-yl)pyridine (bppy) by an aromatic nucleophilic substitution and copper nitrate in hydrothermal conditions led to the formation of a supramolecular framework, formulated as [Cu(pph)2]2MoO4 ·1/2H2O (1). Compound 1 represents a two-dimensional network based on intermolecular O–H⋯O hydrogen bonds, in which Cu(II) is reduced to Cu(I). The formation mechanism of the aromatic nucleophilic substitution was discussed. [Copyright &y& Elsevier]

CuO was synthesized by a simple hydrothermal method and investigated as a heterogeneous activator of persulfate for the degradation of cephalexin and ofloxacin. X-ray photo-electron spectroscopy and hydrogen temperature-programmed reduction measurements reveal that CuO contains two types of Cu2+: one has more electron deficiency (named as Cu2+-h) and the other has relatively higher electron density (named as Cu2+-l). Electron paramagnetic resonance and radical scavenging experiments demonstrate that ·SO4− and ·O2− are responsible for the efficient degradation of cephalexin and ofloxacin, respectively. ·SO4− can be produced through the electron transfer from Cu2+-l to PS and the cleavage of peroxy bond, while ·O2− can be produced via the electron transfer from PS to Cu2+-h and the cleavage of S–O bond. Finally, the degradation intermediates were identified by liquid chromatograph–mass spectrometry. This study proposed a novel mechanism for the activation of persulfate with CuO, which is useful for the rational design of persulfate activator for controlling the production of active species. [ABSTRACT FROM AUTHOR]

CeO 2 was found to be an efficient photocatalyst for the degradation of ciprofloxacin (CIP) under simulated solar light irradiation. The solution pH significantly affected the degradation efficiency and the optimized pH was in the range of 6–9. The scavenger experiment indicates that the photogenerated hole were the main active species for CIP degradation. The interaction between CIP and CeO 2 was investigated by ultraviolet-visible diffuse reflectance, electron paramagnetic resonance and X-ray photoelectron spectra. The results demonstrate the electron transfer from the adsorbed CIP to CeO 2. The activated CIP can be readily degraded by the holes. This suggests that the interaction between pollutants and photocatalyst plays an important role in pollutants removal. Finally, the intermediates were identified and a possible pathway for CIP degradation was proposed. [ABSTRACT FROM AUTHOR]

Review: 155 refs. [ABSTRACT FROM AUTHOR]

Three new polyoxometalate (POM) supramolecular assemblies constructed from phosphotungstate clusters and S-containing pyridine-based cations had been successfully isolated and characterized. Structural analysis revealed that their formula were (H2PySSPy)3[PW12O40]2·6H2O (1), (H3/2PySPy)2[PW12O40]·6H2O (2) and [Ag(HPyS)]4[Ag8(H2O)9][P2W18O62]2·4H2O (3) (PySSPy = 4,4′-dipyridine disulfide; PySPy = 4,4′-thiodipyridine; PySH = pyridine-4-thiol), respectively. The three crystals were assembled by means of multiple weak intermolecular cooperative interactions of hydrogen bonding, S…O, C–H…π, etc. In particular, the peculiar supramolecular bond of the ‘polyanion–π’ binding interaction between the polyanion receptor and the six-membered pyridine ring was described in some detail. These complex and noncovalent contacts efficiently induce the construction of the crystal supramolecular lattices of 1–3. During the formation process of 2 and 3, organic moieties were achieved through the in situ cleavage of S–S chemical bonds in PySSPy. Crystal 3 contains a 3D network constructed from Dawson-like polyanions and Ag–PyS cationic units through Ag–O and Ag–S coordination bonds. One anionic [P2W18O62]6− cluster is bonded to eighteen Ag ions through many Ag–O interactions, presenting an interesting Ag18-supported Dawson structure. [ABSTRACT FROM AUTHOR]

A paramagnetic ferroferric oxide-calcined layered double hydroxide core–shell adsorbent was prepared with high selectivity to anionic pollutions. [Display omitted] • Fe 3 O 4 @cLDH core–shell adsorbent was prepared by the calcination of PB@LDH. • Fe 3 O 4 @cLDH adsorbent exhibits high anionic dye selectivity. • The paramagnetic Fe 3 O 4 @cLDH can be easily collected by a magnet. • The adsorption capability is affected by the pH and soluble CO 2 in aqueous solution. 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 (Fe 3 O 4). It is intriguing to build some reusable adsorbents with magnetic separation by integrating LDH and PB. In this work, paramagnetic Fe 3 O 4 -calcined LDH (Fe 3 O 4 @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 Fe 3 O 4 @cLDH come from the Fe 3 O 4 core and calcined ZnAl-LDH shell, respectively. Fe 3 O 4 @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 Fe 3 O 4 core and calcined ZnAl-LDH shell makes Fe 3 O 4 @cLDH an excellent magnetic separation adsorbent with high selectivity to anions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Fe-Mn oxide was prepared via a new method of redox–precipitation and aging. • Fe was doped in MnO 2 lattice and resulted in structural distortion. • The morphology of MnO 2 material was transformed from nanowires to nanoparticles. • The mechanism of morphological evolution of the material was proposed. • The Fe-Mn oxides showed high activity for o -xylene catalytic oxidation. Fe-MnO 2 nanocomposite was prepared via a redox–precipitation method combined with a subsequent aging treatment at low-temperature. Various characterizations showed that Fe was incorporated into MnO 2 lattice that changed the relative intensity of MnO 2 crystal planes. Thus, the structural defect was formed and the anisotropic growth of the MnO 2 crystallite phase was suppressed. As a result, the morphology of MnO 2 was transformed from nanowires to nanoparticles. In addition, the catalytic property of Fe-MnO 2 was significantly enhanced than that of pristine MnO 2 for the complete oxidation of o -xylene. This work provides a simple and effective strategy for regulating MnO 2 texture and activity. [ABSTRACT FROM AUTHOR]

Photocatalytic CO 2 reduction has drawn widespread attention across all sectors of society. Layered double hydroxides (LDHs) have emerged as promising photocatalysts, renowned for their adjustable bandgaps and reaction sites. As a typical anionic layered material, LDHs exhibit intricate interactions between interlayer anions and brucite-like metal layers, greatly influencing their inherent physicochemical properties. In this work, we synthesized ZnAl-LDH samples intercalated with four distinct anions: carbonate (CO 3 2–), chloridion (Cl–), nitrate (NO 3 –), and dodecyl sulfate (DS–), denoted as LDH-CO 3 , LDH-Cl, LDH-NO 3 , and LDH-DS, respectively. These LDHs samples have comparable crystallinity and morphology but differ in their interlayer spacing. XRD results reveal interlayer spacings of 0.77 nm for LDH-CO 3 , 0.78 nm for LDH-Cl, 0.88 nm for LDH-NO 3 , and 1.24 nm for LDH-DS, between adjacent brucite-like ZnAl hydroxide layers. Remarkably, LDH-NO 3 demonstrates the highest photocatalytic CO 2 reduction performance, with CO as the primary reduction product. Specifically, the average CO production rate of LDH-NO 3 are 3.80 μmol g–1 h–1, surpassing that of LDH-CO 3 , LDH-Cl, and LDH-DS by 1.9, 2.1, and 2.5 times, respectively. This superior performance can be attributed to the intermediate interlayer spacing of LDH-NO 3 , which facilitates strong light absorption and a robust local built-in electric field. Theses properties enhance charge generation and separation abilities, leading to efficient photocatalytic reactions. The obtained results highlight the critical role of controlling small molecules within the interlayer, alongside defects, in the design and fabrication of layered-structure photocatalysts. This study provides valuable insights into optimizing the performance of LDH-based photocatalysts for CO 2 reduction and potentially other photocatalytic applications. [Display omitted] • Four ZnAl-LDH samples with varying anion intercalation were prepared. • ZnAl-LDHs with CO 3 2–, Cl–, NO 3 –, and DS– anions intercalated exhibited increased interlayer spacing. • Among these ZnAl-LDH samples, LDH-NO 3 displayed the highest photocatalytic performance. • The intermediate interlayer spacing of LDH-NO 3 possesses strong local charge separation driving force. [ABSTRACT FROM AUTHOR]

The mismatched interfaces of heterojunction usually have lots of defects, deriving in recombination of generated electron-hole pairs. On the other hand, homojunction interfaces are considered to be beneficial to the separation of charge carriers due to the similar characteristics in two sides of homojunction. TiO 2 have rutile and anatase two typical photoactive phases in nature. In this work, TiO 2 -rutile/anatase (TiO 2 -R/A) homojunction photoanode is fabricated by in situ growth of anatase TiO 2 on TiO 2 -R surface. By contrast with TiO 2 -rutile/rutile (TiO 2 -R/R) photoanode, TiO 2 -R/A displays higher photocurrent density (1.70 mA cm−2 at 0.6 V vs. SCE). Deep insight into the mechanism suggests that TiO 2 -R/A homojunction has intense band bending and enhanced surface area, which facilitate the charge separation and transmission. This study offers some novel insights to design and fabricate semiconductors photoanodes for highly efficient photocatalytic reactions. • TiO 2 -rutile/anatase homojunction photoanode is fabricated by in situ growth method. • TiO 2 -rutile/anatase homojunction interface has less recombination centers of charge carriers. • Photo-induced change of Fermi level suggests the extended depletion layer in TiO 2 -rutile/anatase photoanode. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Two new coordination polymers {[Ag(bpe)] 4 V 6 O 17 } n (1) and {[Ag(bpe)] 10 V 14 O 40 } n ∙3nH 2 O (2) (bpe = 1,2-di(4-pyridyl)ethylene) had been synthesized by hydrothermal methods, and characterized by elemental analysis, IR, UV–vis, TG, XRD and single-crystal X-ray diffraction. Structural analysis revealed that they both consist of {VO 4 }-based chain-like polyanions and {Ag-bpe} cationic units. The structural differences of 1–2 clearly showed that the polyoxovanadates are sensitive to the dosages of NH 4 VO 3 source in synthesis reaction. The aromatic π...π stacking and Ag...Ag weak interactions among {Ag-bpe} cationic units contribute the significant effect on the stability of 3D crystal structures. The catalytic properties of the synthesized crystals were tested. It was found that the photochemical degradation of MB can reach 74.2% in 90 min by using 1 as catalyst. Graphical abstract Two Ag-ligand modified vandates had been synthesized and characterized, which the inorganic moieties present chain-like {VO 4 } ∞ arrangement consisting of four/five-membered {VO 4 } rings bridged by {VO 4 } 2 subunits via oxygen-shared modes. fx1 Highlights • Two new coordination polymers have been synthesized and characterized. • The structures of crystals are stabilized by weak π...π and Ag...Ag interactions. • The formation of V-O clusters is senstitive to the reaction condition. [ABSTRACT FROM AUTHOR]

The development of efficient magnetic adsorbents is highly desirable for water treatment. In this work, MnFe2O4 and Fe3O4 were prepared by a lignosulfonate-assisted hydrothermal method. The structure, surface property and adsorption capacity of the products were investigated. The obtained products have a small amount of carbonaceous materials, mesoporous structure and narrow pore size distribution. In comparison with the samples prepared without lignosulfonate, they have more surface hydroxyl groups and highly negatively charged surface in aqueous solution, which favor the adsorption of cations. Fe3O4 and especially MnFe2O4 exhibited high adsorption capacity towards Pb(II). The maximal removal efficiency of Pb(II) (50mgL) on MnFe2O4 was 100% at pH 6.2. The results demonstrate that this method is promising for the synthesis of magnetic adsorbent. Mesoporous MnFe2O4 and Fe3O4 containing a small amount of carbonaceous materials were successfully prepared by a simple lignosulfonate-assisted hydrothermal method. The as-obtained samples exhibited high adsorption capacity for Pb(II) removal due to their abundant surface hydroxyl groups and highly negatively charged surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag or Cu doped OMS-2 was prepared by a one-step reduction method. • It exhibited excellent low-temperature catalytic activity for o -xylene oxidation. • The doped Ag and Cu had different effects on the structure and property of OMS-2. • The role of oxygen species in the catalytic oxidation of o -xylene was discussed. Ag or Cu doped manganese oxide octahedral molecular sieve (OMS-2) was prepared through the one-step reduction of KMnO 4 , Tollens' reagent, or Fehling' reagent with propionaldehyde. The influences of the dopants on the structure, redox ability and catalytic performance of OMS-2 were investigated. The results indicate that Ag-OMS-2 and Cu-OMS-2 exhibited relatively higher catalytic activity for o -xylene oxidation at higher (>185 °C) and lower temperatures (≤185 °C), respectively. This can be illustrated as follows. The doped Ag increased the content of surface absorbed oxygen and inhibited the adsorption of CO 2. The doped Cu increased the content of lattice oxygen and the surface area of OMS-2, but increased its adsorption capacity toward CO 2. In situ DRIFT study demonstrates that the oxidation of low molecular weight carboxylates (the stable intermediates in the oxidation of o -xylene) is the rate-determining step, which is closely related with the active oxygen species. The doped Ag increased the content of electrophilic oxygen (O 2 −, O− or O 2 2−) and promoted the transformation of O 2 into nucleophilic oxygen (O2−), which facilitated the oxidation of benzene ring and small molecule carboxylate, respectively. [ABSTRACT FROM AUTHOR]

Manganese oxide octahedral molecular sieve (OMS-2) with different microstructures were synthesized via simple wet chemical methods of KMnO 4 /benzyl alcohol and KMnO 4 /Mn(NO 3 ) 2 at room-temperature (the products were denoted as B-OMS-2 and N-OMS-2, respectively). The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o -xylene. It was found that B-OMS-2 presented a loose structure, and contained almost 100% Mn 4+ , while N-OMS-2 possessed a mixture of Mn 4+ and Mn 3+ . H 2 -TPR and O 2 -TPO analyses showed that B-OMS-2 exhibited good low-temperature reducibility and high oxygen exchange ability with gas phase oxygen. The microstructure difference was caused by different reducing reagents used in the synthesis. Benzyl alcohol might adsorb on the surface of MnO 2 nuclei acting as a ligand and/or structure-directing agent, and the desorption of the organic compound led to the formation of bulk oxygen vacancy in B-OMS-2. B-OMS-2 could convert 100% o -xylene into CO 2 at 190 °C at a space velocity of 8000 h −1 , 50 °C lower than N-OMS-2. The excellent catalytic performance of B-OMS-2 might be caused by its bulk oxygen vacancy, potent reducibility and high re-oxidation ability. It is believed that B-OMS-2 is a promising catalyst for the elimination of VOCs from air. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous α-MnO2 and β-MnO2 were prepared using KMnO4 and H2C2O4 (Oxalate) as precursors via aqueous and hydrothermal routes respectively. The morphological and structural evolution of the MnO2 materials were tracked by Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The preparation of MnO2 materials was found to proceed through four steps: well-crystallized α-MnO2 was formed first in aqueous solution, and then translated into microcrystalline α-MnO2 microspheres consisting of nanoparticles and nanowires via a dissolution-recrystallization process. Subsequently, the microcrystalline α-MnO2 microspheres collapsed, and γ-MnOOH nanowires were formed. Finally, β-MnO2 nanowires were obtained after calcining the γ-MnOOH nanowires in air at 400°C for 6h. During the process, oxalate acted as an important reagent and played an important role for the structural and morphological evolution of MnO2. Nitrogen sorption analysis showed that the as-prepared α-MnO2 and β-MnO2 materials all exhibited type IV isotherms, indicating mesoporous characters. In addition, the performance of the MnO2 materials as a catalyst was evaluated in the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene. [Copyright &y& Elsevier]

Nickel and cobalt phosphates as a kind of low-cost inorganic materials are promising electroactive materials. The structure stability and good dispersibility of micro-spherical materials make them popular in the energy storage field. Therefore, the fabrications of Ni–Co phosphate microspheres with some facile and cost-effective methods have attracted lots of attentions. In this work, we present one-step growth of Ni 2 Co(PO 4) 2 microspheres using urea as pH regulator. Urea decomposes into NH 3 and CO 2 during the hydrothermal reaction process, resulting in the precipitation of Ni–Co phosphates. The as-prepared Ni 2 Co(PO 4) 2 microspheres exhibit uniform and well-dispersed spherical morphology. Compared with traditional Ni 2 Co(PO 4) 2 particles, Ni 2 Co(PO 4) 2 microspheres exhibit larger electrochemical specific surface area and smaller resistance of electrons/ions transfer. The specific capacity of Ni 2 Co(PO 4) 2 microspheres reaches as high as 153 mAh g-1 at a current density of 1 A g-1, which is 1.59 times higher than that of traditional Ni 2 Co(PO 4) 2 particles. In addition, this facile one-step synthetic method can be applied to fabricate series of Ni–Co phosphates with different Ni/Co atomic ratios. This work provides a facile synthetic method of fabricating Ni–Co phosphate materials, which has potential applications in large-scale manufacture. [Display omitted] • Ni 2 Co(PO 4) 2 microspheres were prepared by a facile one-step growth method. • No assisted surfactants or templates were added in the preparation process. • The as-prepared Ni 2 Co(PO 4) 2 microspheres present high capacity and good stability. [ABSTRACT FROM AUTHOR]

Abstract: P-doped cryptomelane-type manganese oxide K-OMS-2 materials with three-dimensional structures were easily prepared using KMnO4 and MnPO4 as precursors via hydrothermal route. The scanning electron microscopy (SEM) and Energy dispersive X-ray spectra (EDS) results revealed that the morphology of P-doped K-OMS-2 transformed from hierarchical microspheres assembled from nanosheets and nanoneedles to nest-like structure with the increase of P/Mn molar ratio. Nitrogen sorption analysis showed that the isotherms of P-doped K-OMS-2 materials were typically type-IV with hysteresis loops, which meant that the samples had a mesoporous structure. The surface area and average pore diameter of the as-prepared K-OMS-2 materials were 138–153m2 g−1 and 18–56nm respectively. In addition, the obtained materials showed good catalytic ability for the catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: A novel redox-precipitation method was developed for the preparation of α-MnO2, where Mn(NO3)2 and KOH were titrated into excess KMnO4 solution at pH 8. For comparison, MnO x was also prepared using a conventional precipitation method. These materials were characterized by XRD, BET, SEM/EDS, XPS, and H2-TPR techniques, and their catalytic activities were evaluated for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene. The novel method produced open porous hierarchically structured microcrystalline α-MnO2 containing almost 100% Mn4+ ion on its surface. Whereas, the conventional precipitation method produced a mixture of MnO2 and Mn3O4 with a closely packed spherical morphology containing only 31% Mn4+ ion on its surface. It was found that α-MnO2 exhibited good low-temperature reducibility, and that it could convert 100% o-xylene into CO2 at 220°C at a space velocity of 8000h−1, 50°C lower than the MnO x prepared by the conventional method. The surface concentration of Mn4+ ion in α-MnO2 played a key role for its high catalytic activity for the complete oxidation of o-xylene. In addition, the open porous structure and the presence of small amount of potassium ion in the microcrystalline α-MnO2 channel may also be responsible for its excellent catalytic performance. Effects of pH and calcination temperature on its catalytic activity were investigated, and optimal preparation conditions were found. Durability of the α-MnO2 was also studied. [Copyright &y& Elsevier]

Abstract: Uniform mesoporous β-Ni(OH)2 and NiO nanospheres with hierarchical structures were synthesized by a facile complexation–precipitation method. The effects of ammonia and citrate on the structure and morphology of the products were thoroughly investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements. The results indicated that ammonia played an important role for the formation of flowerlike spheres assembled from nanosheets. The addition of citrate could remarkably reduce the particle sizes and increase the specific surface areas of flowerlike spheres. A possible formation mechanism based on the experimental results was proposed to understand their growing procedures. β-Ni(OH)2 and NiO nanospheres prepared with the addition of citrate showed excellent capacitive properties due to their mesoporous structures and large surface areas, suggesting the importance of controlled synthesis of hierarchical nanostructures for their applications. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Various MnO structures have been synthesized in this study by a facile method through the manipulation of KMnO concentration. The effect of KMnO concentration on the structure and morphology has been thoroughly investigated by X-ray powder diffraction, field-emission scanning electron microscopy, and nitrogen adsorption-desorption measurements. Birnessite-type MnO flower-like microsphere can be obtained at a lower concentration, while α-MnO nanorods can be obtained at a higher concentration. By increasing the KMnO concentration further, α-MnO nanorods can assemble into urchin-like microspheres and spherical aggregates. The possible formation mechanism based on the experimental results has been proposed to understand their growth procedures. The electrochemical properties of the synthesized materials evaluated by cyclic voltammetry and constant-current charge-discharge cycling techniques are dependent on their pore size distribution and nanostructures. Birnessite-type MnO microsphere showed excellent capacitive behavior with a maximum specific capacitance of 185 F g. [ABSTRACT FROM AUTHOR]

Abstract: Molecular assembly processes by utilizing the template-directing effect of anionic polyoxometalate clusters and the flexible organic cation have achieved three hybrids: (H2bpp)(Hbpp)[PMo12O40]·3DMF (1), (H2bpp)(Hbpp)(bpp)2 [PMo9V3O40(VO)2]2 (2), and (H2bpp)2[β-Mo8O26] (3) (bpp=1,3-bis(4-pyridyl)propane). Three compounds were characterized using single crystal X-ray crystallography, elemental analysis, IR, XPS, EPR, voltammetric behavior and TGA. Crystal structural analyses revealed that compounds 1–3 were all constructed from protonated organic bpp cations with different POM clusters: isolated α-Keggin P–Mo cluster in 1; dimer of bi-capped α-Keggin P–Mo–V anions linked through a {V2O2} unit in 2; β-octamolybdate isopolyanion in 3, respectively. All three assemblies demonstrated a higher thermal stability. The protonated bpp cations lost at temperature higher than 300°C that the strong intermolecular interactions may account for the high initial temperature of weight loss. The electrochemistry property of compound 2 modified carbon paste electrode was also studied in 1M H2SO4 aqueous. [Copyright &y& Elsevier]

Layered double hydroxides (LDHs) are a class of 2D structure anionic clays with tunable structure, which has high theoretic faradaic capacitance. However, self-aggregation of LDHs nanosheet usually restricts their energy storage performances. Microspheres materials possess high specific surface area and structure stability, which provide a promising method to address the issue of aggregation in LDHs nanosheet. In this work, we present the one-step fabrication of NiCoAl-LDH microspheres with well-dispersed morphology and high electrochemically active surface area. The fabricated Ni 1 Co 2 Al 1 -LDH microspheres present specific capacitance of 451 F g−1 at current density of 5 A g−1, which is 1.92 times higher than that of conventional lamellar Ni 1 Co 2 Al 1 -LDH. Based on the Ni 1 Co 2 Al 1 -LDH microspheres, an all-solid-state asymmetric supercapacitor device was fabricated, giving high energy density, power density and long term cycling stability. This one-step growth of NiCoAl-LDH microspheres method has potential applications in large-scale manufacture of energy storage materials. Image 1 • Self-aggregation of LDHs nanosheet restricts their energy storage performances. • LDHs microspheres materials draw lots of attention due to the high specific surface area and structure stability. • NiCoAl-LDH microspheres were prepared by one-step growth method. • This one-step growth method has potential applications in large-scale manufacture. [ABSTRACT FROM AUTHOR]

Abstract: Mn–Co oxide hierarchical structure assembled from nanosheets was prepared by a simple method. The structure, surface property and adsorption capacity of the product were investigated. The characterization results confirm that the Co ions are incorporated into the structure of MnO2. In comparison with MnO2, the obtained composite oxide has a more highly negatively charged surface in aqueous solution, thus enhancing its adsorption capacity for heavy metal ions. The maximal adsorption capacities of Mn–Co oxide are 656 and 762mgg−1 for Pb2+ and Cu2+, respectively. The results demonstrate that the Mn–Co oxide is a promising adsorbent for the removal of heavy metals from aqueous solution. [Copyright &y& Elsevier]

Abstract: Mesoporous α-MnO2 nanorods were easily prepared using KMnO4 and MnCO3 as precursors via hydrothermal route without any template. The transmission electron microscopy (TEM) observations revealed that the obtained α-MnO2 had three-dimensional frameworks. Nitrogen sorption analysis showed that the α-MnO2 nanorods exhibited a type IV isotherm, indicating a mesoporous character with adsorption average pore diameter of 18.0nm, mesoporous volume of 0.16cm3 g−1, and Brunauer–Emmett–Teller specific surface area of 176m2 g−1. The obtained nanorods showed superior catalytic ability for the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene, which can be due to its mesoporous structure and large surface area. [Copyright &y& Elsevier]

Abstract: Mesoporous α-Ni(OH)2 was synthesized by a facile method and investigated as an electrochemical pseudocapacitor material. Structural characterizations reveal that the mesoporous α-Ni(OH)2 has a narrow pore size distribution of 16nm and a large surface area of 349m2 g−1. The α-Ni(OH)2 sample exhibits excellent electrochemical performance at different current densities and good cycling ability, which can be due to its mesoporous structure and large surface area. A maximum specific capacitance of 1718Fg−1 can be achieved at a scan rate of 5mVs−1. These results indicate that the mesoporous α-Ni(OH)2 is a promising candidate for the supercapacitor electrodes. [Copyright &y& Elsevier]

• CuO-persulfate exhibited high activity for the removal of ciprofloxacin. • Bicarbonate had positive effect on the CuO-persulfate process. • The active species for ciprofloxacin degradation were dependent on solution pH. CuO synthesized by a hydrothermal method was used to activate persulfate (PS) for removing ciprofloxacin (CIP) in water. The influences of reaction parameters and coexisting substances on this process were studied. Under the optimal conditions ([CuO] 0 = 6.3 mmol L−1, [PS] 0 = 1 mmol L−1, pH 8), CIP was completely degraded and the total organic carbon removal efficiency was 84.2%. Ca2+, Mg2+ and Cl− had little effect on CIP removal, while fulvic acid showed a slight inhibitory effect. By contrast, bicarbonate enhanced CIP degradation and significantly suppressed Cu leaching. Subsequently, the reactive species for CIP degradation were identified by electron paramagnetic resonance and radical scavenging experiments. Although the decomposition efficiency of PS was significantly accelerated by increasing pH, similar amounts of O 2 −, OH, SO 4 − and 1O 2 were detected at different pH, suggesting the formation of more surface activated PS at higher pH. The reactive species for CIP degradation were found to be dependent on solution pH. CIP was mainly degraded by SO 4 − and 1O 2 at acidic conditions. The activated PS might have high selectivity towards CIP and its amount might be higher than that of radicals at pH 8. In addition, the uncharged surface of CuO at pH 8 facilitated the adsorption of CIP, which is beneficial to the surface reaction between CIP and activated PS. Hence, the activated PS was the dominated species for CIP degradation at this pH. [ABSTRACT FROM AUTHOR]

The sandwich-type polyoxometalate Na8Li12 [Ni2(P2W15O56)2] ·74H2O (I) is obtained by slow evaporation of a solution containing NiCl2 and Na3PO4 in 4 M LiCl at pH 8 to which Na12[α-P2W15O56] is added (60 °C, 1 h, 40% yield). [ABSTRACT FROM AUTHOR]