Adsorption Behavior of Rhodamine B on UiO-66

The adsorption characteristics of UiO-66 (a Zr-containing metal–organic framework formed by terephthalate) for Rhodamine B (RhB), such as isotherms, kinetics and thermodynamics, were investigated systematically. The batch adsorption data conform well to the Langmuir and Freundlich isotherms. The adsorption kinetics of UiO-66 for RhB can be well described by the pseudo first-order model, and the adsorption thermodynamic parameters ΔG₀, ΔH₀ and ΔS₀ at 273 K are − 6.282 kJ·mol^− 1, 15.096 kJ·mol^− 1 and 78.052 J·mol^− 1·K^− 1, respectively. The thermodynamic analyses show that the adsorption process of RhB on UiO-66 is more favorable at higher temperatures. UiO-66 can be regenerated by desorbing in DMF solution with ultrasonic for 1 h. UiO-66 can keep good performance for at least six cycles of sorption/desorption.     

Mesoporous CuO/TixZr1 − xO2 catalysts for low-temperature CO oxidation

Mesoporous CuO/Ti_xZr_1 − xO₂ catalysts were prepared by a surfactant-assisted method, and characterized by N₂ adsorption/desorption, TEM, XPS, in-situ FTIR and H₂-TPR. The catalysts exhibited high specific surface area (S_BET = 241 m²/g) and uniform pore size distribution. XPS and in-situ FTIR displayed that Cu⁺ and Cu²⁺ species coexisted in the catalysts. The CuO/Ti_xZr_1 − xO₂ catalysts presented obviously higher activity in CO oxidation reaction than the CuO/TiO₂ and CuO/ZrO₂ catalysts. Effect of molar ratios of Ti to Zr and calcination temperature on catalytic activity was investigated. The CuO/Ti_0.6Zr_0.4O₂ catalyst calcined at 400 °C exhibited excellent activity with 100% CO conversion at 140 °C.     

Hydrazine hydrate-induced hydrothermal synthesis of MnFe2O4 nanoparticles dispersed on graphene as high-performance anode material for lithium ion batteries

Herein, a MnFe₂O₄/graphene (MnFe₂O₄/G) nanocomposite has been synthesized via a facile N₂H₄·H₂O-induced hydrothermal method. During the synthesis, N₂H₄·H₂O is employed to not only reduce graphene oxide to graphene, but also prevent the oxidation of Mn²⁺ in alkaline aqueous solution, thus ensuring the formation of MnFe₂O₄/G. Moreover, MnFe₂O₄ nanoparticles (5–20 nm) are uniformly anchored on graphene. MnFe₂O₄/G electrode delivers a large reversible capacity of 768 mA h g⁻¹ at 1 A g⁻¹ after 200 cycles and high rate capability of 517 mA h g⁻¹ at 5 A g⁻¹. MnFe₂O₄/G holds great promise as anode material in practical applications due to the outstanding electrochemical performance combined with the facile synthesis strategy.     

Low-temperature synthesis of copper oxide (CuO) nanostructures with temperature-controlled morphological variations

We demonstrate low-temperature formation of copper oxide (CuO) nanostructures as well as temperature-controlled variation of morphology by applying hydrothermal methods with copper(II) acetate Cu(CH₃COO)₂·H₂O and 2-piperidinemethanol (2PPM) as starting materials. Monoclinic CuO nanostructures produced at 25 °C were of dendritic morphology with short nanorod-like substructures and exhibited a consequently large surface area (179 m² g⁻¹). Cyclic voltammetry measurements confirmed pseudocapacitive behavior of these dendritic CuO nanostructures giving specific capacitance ca. 28.2 F g⁻¹ at a scan rate of 5 mV s⁻¹. Oxide nanomaterials prepared in this investigation were characterized using powder X-ray diffraction, scanning and transmission electron microscopies, and nitrogen adsorption/desorption techniques. It is expected that these materials exhibit improved sensing and catalytic properties due to the increased availability of surface adsorption sites.     

Synthesis and characterization of nickel phosphonopropionate hybrid materials

Hydrothermal reaction of nickel acetate with 3-phosphonopropionic acid and 4,4′-bipyridine resulted in two novel phosphonate compounds Ni(HO₃PC₂H₄COO)(4,4′-bpy)(H₂O) · 0.5(4,4′-bpy) (bpy = bipyridine) (I) and Ni(O₃PC₂H₄COOH)(4,4′-bpy)(H₂O)₃ · H₂O (II). Single-crystal X-ray studies reveal that self-assemblies between the ligands and metal ion result in layer (I) and chain (II) structures. Magnetic measurement of I indicate there are ferromagnetic couplings between adjacent Ni²⁺ ions (C = 1.29 cm³ mol⁻¹ K and θ = 2.25 K).     

Synthesis,crystal structure,luminescence and thermal behavior of a new energetic zinc(II) compound

An energetic material [Zn₂(btzphda)₂(H₂O)₄(dpp)₂]·2DMF·4H₂O with high decomposition enthalpy of − 748.35 J/g was prepared by the reaction of H₂btzphda, dpp and Zn(NO₃)₂·6H₂O under solvothermal conditions, where btzphda = 1,4-bis(tetrazol-5-yl)benzene-N2,N2′-diacetato, dpp = 1.3-di(4-pyridyl)propane and DMF = N,N′-dimethylformamide. The luminescence properties of H₂btzphda and [Zn₂(btzphda)₂(H₂O)₄(dpp)₂]·2DMF·4H₂O were investigated at room temperature in the solid state (Hitachi F4600 spectrofluorometer). Furthermore, the thermal decomposition behavior of the compound is characterized by differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses. The entropy of activation (ΔH), enthalpy of activation (ΔS) and the free energy of activation (ΔG) for the decomposition temperature were ΔH = 250.64 kJ/mol, ΔS = 222.75 J·mol^− 1·K^− 1 and ΔG = 134.10 kJ/mol.     

The effects of the surface oxidation of activated carbon,the solution pH and the temperature on adsorption of ibuprofen

A commercial microporous–mesoporous granular activated carbon was modified by oxidation with either H₂O₂ in the presence or absence of ultrasonic irradiation, or NaOCl or by a thermal treatment under nitrogen flow. Raw and modified materials were characterized by N₂ adsorption–desorption measurements at 77 K, Boehm titrations, pH measurements and X-ray photoelectron spectroscopy. Ibuprofen adsorption kinetic and isotherm studies were carried out at pH 3 and 7 on raw and modified materials. The thermodynamic parameters of adsorption were calculated from the isotherms obtained at 298, 313 and 328 K. The pore size distribution of carbon loaded with ibuprofen brought out that adsorption occurred preferentially into the ultramicropores. The adsorption of ibuprofen on pristine activated carbon was found endothermic, spontaneous (ΔG° = −1.1 kJ mol⁻¹), and promoted at acidic pH through dispersive interactions. All explored oxidative treatments led mainly to the formation of carbonyl groups and in a less extent to lactonic and carboxylic groups. This then helped to enhance the adsorption uptake while decreasing adsorption Gibbs energy (notably −7.3 kJ mol⁻¹ after sonication in H₂O₂). The decrease of the adsorption capacity after bleaching was attributed to the presence of phenolic groups.     

Optimization of desulphurization of Artvin–Yusufeli lignite with acidic hydrogen peroxide solutions

In this study in which the Taguchi method was used, the optimization of sulphur removal by H₂O₂/H₂SO₄ solutions was carried out over lignite with higher content of sulphur from Artvin/Yusufeli, Turkey. In experiments, the ranges of experimental parameters were between 0.25 and 6.0 mol L⁻¹ for H₂O₂ concentration, 0.25–4 mol L⁻¹ for H₂SO₄ concentration, 10–60 °C for reaction temperature, 0.01–0.08 g mL⁻¹ for solid-to-liquid ratio, 15–120 min for reaction time, 200–300 rpm for stirring speed and 710–120 μm for particle size. The optimum conditions for these parameters have found to be 60 °C of temperature, 0.06 g mL⁻¹ of solid-to-liquid ratio, 60 min of reaction time, 250 rpm of stirring speed and −250 + 180 μm of particle size.A statistical experimental arrangement, L₂₅(5⁶) was prepared to determine optimum sulphur removal and ash removal ratios. The obtained yields were 97.85% in removal of total sulphur, 56.54% in removal of pyritic sulphur, 21.33% in removal of organic sulphur and 61.52% in removal of ash. According to variance analysis, it was seen that all parameters were effective in removal of pyritic and total sulphur, reaction temperature, solid-to-liquid ratio, reaction time, stirring speed, H₂O₂ and H₂SO₄ concentrations in removal of organic sulphur, and other parameters except acid concentration in removal of ash.     

Synthesis and ethanol sensing properties of CuO nanorods coated with In2O3

CuO/In₂O₃ core–shell nanorods were fabricated using thermal evaporation and radio frequency magnetron sputtering. X-ray diffraction and transmission electron microscopy showed that both the cores and shells were crystalline. The multiple networked CuO/In₂O₃ core–shell nanorod sensors showed responses of 382–804%, response times of 36–54 s and recovery times of 144–154 s at ethanol (C₂H₅OH) concentrations ranging from 50 to 250 ppm at 300 °C. These responses were 2.3–2.8 times higher than those of the pristine CuO nanorod sensor over the same C₂H₅OH concentration range. The origin of the enhanced ethanol sensing properties of the core–shell nanorod sensor is discussed.     

Synthesis,structure and magnetic properties of spinel ferrite (Ni,Cu, Co)Fe2O4 from low nickel matte

Spinel ferrite (Ni, Cu, Co)Fe₂O₄ was synthesized from the low nickel matte by using a co-precipitation-calcination method for the first time. The influences of the added amount of NiCl₂·6H₂O, calcination temperature and time on the structure and magnetic properties of the as-prepared ferrites were studied in detail by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, and Vibrating sample magnetometer (VSM). It is indicated that pure (Ni, Cu, Co)Fe₂O₄ with cubic phase could be obtained under the experimental conditions (NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, calcination temperature from 800 to 1000 °C and calcination time from 1 to 3 h). With increasing calcination temperature and time, saturation magnetization (M_S) of the synthesized (Ni, Cu, Co)Fe₂O₄ increased and the coercivity (H_C) decreased. Under the optimum conditions (i.e. NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, 1000 °C, 3 h), the M_S and H_C values of the product were approximately 46.1 emu g⁻¹ and 51.0 Oe, respectively, which were competitive to those of other nickel ferrites synthesized from pure chemical reagents. This method explores a novel pathway for efficient and comprehensive utilization of the low nickel matte.     

A highly efficient and noble metal-free photocatalytic system using NixB/CdS as photocatalyst for visible light H2 production from aqueous solution

Photocatalytic H₂ production from water is one of the most attractive issues for the conversion of solar energy into chemical energy. In this study, the Ni_xB/CdS photocatalyst was firstly used for photocatalytic H₂-evolution reaction and showed efficient visible-light photocatalytic activity and good stability for H₂-evolution from aqueous solution. The optimal Ni_xB loading content was determined to be 0.8 wt.%, and the corresponding H₂-production rate reached up to 4.8 mmol·h^− 1·g^− 1 after a 10 h visible light irradiation. It is proposed that the loading of Ni_xB on the surface of CdS could effectively increase the separation of photo-generated electrons and holes and greatly enhance the photocatalytic activity.     

An artificial photosynthesis system based on CeO2 as light harvester and N-doped graphene Cu(II) complex as artificial metalloenzyme for CO2 reduction to methanol fuel

An artificial photosynthesis catalyst composed of CeO₂, N-doped graphene and copper ions (CeO₂–NG–Cu^2 +) was fabricated. The light-harvesting CeO₂–NG was characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic reduction of CO₂ was conducted in an aqueous solution of Na₂SO₃. Results indicated that the reduction rate of CO₂ to methanol approached 507.3 μmol · g⁻¹ cat. · h^− 1 for CeO₂–NG–Cu^2 + artificial photosynthesis system in 80 min, whereas the reduction rate was only 5.8 μmol · g⁻¹ cat. · h^− 1 for bare CeO₂–NG without metalloenzyme. Therefore, artificial metalloenzyme played a vital role in reducing CO₂ to methanol fuel.     

The size and dispersion effect of modified graphene oxide sheets on the photocatalytic H2 generation activity of TiO2 nanorods

Nano graphene oxide (NGO) was produced by further refluxing graphene oxide (GO) sheets in HNO₃, and carboxylic acid functionalized graphene oxide (GO–COOH) was obtained by a simple etherification reaction between GO and chloroacetic acid. The GO, GO–COOH and NGO sheets are combined with TiO₂ nanorods by a two-phase assembling method, and confirmed by transmission electronic microscopy. The GO–TiO₂, GO–COOH–TiO₂ and NGO–TiO₂ composites are used in a comparative study of photocatalytic H₂ generation activity under UV light irradiation. The H₂ generation rate of TiO₂ nanorods was slightly increased from 15 to 30 mL h⁻¹ g⁻¹ by replacing oleic acid ligands with hydrophilic dopamine, and significantly increased to 105 mL h⁻¹ g⁻¹ after combining with GO sheets. The further comparative study shows that GO–COOH–TiO₂ composite has higher H₂ generation rate of 180 mL h⁻¹ g⁻¹ than that of GO–TiO₂ and NGO–TiO₂ composites.     

A novel dimeric polyanion based on mono-manganese substituted Keggin-type phosphotungstate: (MnPW11O39)210 −

The novel dimeric polyoxometalate, (MnPW₁₁O₃₉)₂^10 − (1a), has been synthesized by reacting [B-α-PW₉O₃₄]^9 − with Mn^2 + ions in weak acid aqueous solution (pH = 5.3) under hydrothermal condition and isolated in the form of (C₁₄H₁₄N₄)₅H₁₀(MnPW₁₁O₃₉)₂·2H₂O (1), which was characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and magnetic measurements. The polyanion represents the first example of dimeric polyanion based on mono-transition metal (TM) substituted Keggin-type polyanions linked by two TM-μ₂-O-TM bridges. Magnetic measurements show that the Mn┄Mn exchange interactions are weakly antiferromagnetic (J = ⁻ 0.53 cm^− 1).     

Nonisothermal sintering of Mn doped ZnO

The sintering of pure ZnO and ZnO doped with Mn, obtained by addition of Mn(NO₃)₂. 4H₂O in the concentration from 0·1 to 1·2 mol%, was investigated by dilatometry at constant heating rates, from 1 to 15 °C min⁻¹. Mn shifts the onset of the sintering towards higher temperatures, but no significant effect of the Mn doping level on the shrinkage was observed. Accordingly, the calculated activation energy for the first stage, changed from ∼320 kJ mol⁻¹ for pure ZnO to ∼440 kJ mol⁻¹ for Mn doped ZnO. Using classical sintering models to analyse the initial stage sintering of all the compositions, two sintering mechanisms were found to control the initial stage sintering. The first region is identified with a grain boundary sliding mechanism, while volume diffusion is the controlling mechanism in the second region. With the increase of the Mn content, the grain boundary sliding rate remains constant, but the volume diffusion rate is reduced.     

Hydrothermal synthesis,structure and properties of two new phosphomolybdates based on Strandberg-type {P2Mo5O23}6 − building units

Two inorganic–organic hybrid compounds based on Strandberg-type phosphomolybdates (abbreviated as {P₂Mo₅O₂₃}^6 −) complexes [H₃O]₂[Cu₂(Pyim)₂(H₂O)₃][P₂Mo₅O₂₃] · 6H₂O (1) and [Cu₃(Pyim)₃(H₂O)₄][P₂Mo₅O₂₃] · 7H₂O (2) were successfully synthesized at different pH values under hydrothermal conditions. Both 1 and 2 are based on the {P₂Mo₅O₂₃}^6 − clusters connected by copper complexes to generate one dimensional chain. The magnetic analyses of compounds 1 and 2 indicate antiferromagnetic interactions between copper ions.     

pH-controlled the formation of 4-sulfocalix[4]arene-based 1D and 2D coordination polymers

Three manganese/4-sulfocalix[4]arene complexes, namely, {H[(C₂₈H₂₀O₁₆S₄)Mn(H₂O)₄Mn_0.5(H₂O)₂]}_n ·6nH₂O (1), {NH₄[(C₂₈H₂₀O₁₆S₄)Mn(H₂O)₄Mn_0.5(H₂O)₂]}_n · 5nH₂O (2), [(C₂₈H₂₀O₁₆S₄)Mn₂(H₂O)₈]_n · 6nH₂O (3), have been synthesized under different pH conditions. Complex 1, which exhibits a one-dimensional (1D) structure, is formed at [H⁺] = 2.0 mol L⁻¹. Reaction at pH 4 leads to another one-dimensional (1D) coordination polymer of 2. At pH 5, a two-dimensional (2D) coordination polymer of complex 3 is formed, showing clearly structural effects on pH response.     

Reversible water inclusion in a porous magnetic material synthesized from copper(II) incorporated metal-organic framework showing alternate ferro- and antiferromagnetic interactions

X-ray structural analysis shows that {[Cu₂(CTA) (H₂O)] · 5 H₂O}_n constitutes infinite one-dimensional parallel chains along the c-axis with water columns running down the crystallographic a-axis. The inclusion of water molecules is reversible and is confirmed by X-ray powder diffraction studies. The magnetic data (2–300 K) reveal that there are alternate ferro- (J = 0.29 cm⁻¹) and antiferromagnetic (J = −2.5 cm⁻¹) interactions.     

Visual and Raman spectroscopic observations of hot compressed water oxidation of guaiacol in fused silica capillary reactors

Using fused silica capillary reactors (FSCRs), we investigated the decomposition of guaiacol during hot compressed water oxidation (HCWO), with H₂O₂ added in stoichiometric ratios from 100 to 300%. Reactions were performed between 180 and 300 °C for durations from 2 to 10 min while the concurrent generation of CO₂ during the oxidation process was followed by Raman spectroscopy and the phase behavior of guaiacol in HCW, with or without H₂O₂, was observed visually under a polarized microscope configured with a heating/cooling stage. We found that complete conversion of guaiacol and 100% yield of CO₂ were achieved with a 150% stoichiometric ratio of oxidizer after 10 min at 200 and 300 °C, respectively. Based on the global reaction kinetics for the complete conversion of guaiacol to CO₂, the reaction is considered to be first order. The activation energy and pre-exponential factor for CO₂ formation are 18.62 kJ mol⁻¹ and 12.81 s⁻¹, respectively.     

A novel glass fiber catalyst for the catalytic combustion of ethyl acetate

Supported CuO catalysts were prepared by wet impregnation into novel glass fiber corrugated honeycomb supports, and the catalytic combustion of ethyl acetate and the effect of copper loading were examined. Among the catalysts tested, Cu10/Al₂O₃-M showed the highest activity. For the catalyst, 100% conversion of ethyl acetate was achieved at 300 °C, feed concentration of 1802 mg/m³ and the space velocity of 5000 h^− 1. To reveal these phenomena, the supports and catalysts were characterized by SEM, BET, XRD, H₂-TPR and ethyl acetate-TPD. The catalyst activity was strongly related to the amount of highly dispersed CuO species and suitable porosity.