Several composite catalysts were simply prepared by growing a MoS2 sheet on N-doped mesoporous graphic carbon derived from ZIF-8. The as-prepared catalysts were well characterized by transmission electron microscopy (TEM), Raman spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption analysis. The catalysts have shown greatly improved electrocatalytic performance in the hydrogen evolution reaction (HER) in 0.5 M H2SO4 compared to the corresponding MoS2, and as low as 185 mV of overpotential at 10 mA/cm2 and 57.0 mV/decade of Tafel slope were obtained. The catalyst also exhibits great stability, and only an 18 mV increase in overpotential was observed after 1000 cycles.Keywords: Hydrogen evolution reaction; Metal−organic framework; Molybdenum disulfide; N-doped mesoporous carbon;

Silica-supported magnetic cobalt ferrite complex oxides, CoFe2O4/SiO2, with different loading of 5, 10, 20, and 50% were simply prepared by a sol–gel autocombustion method using colloidal aqueous silica solution as a cheap silica source. The as-prepared samples were well characterized by X-ray diffractometry (XRD), Fourier transform infrared spectrophotometry (FT-IR), transmission electron microscopy (TEM), and N2 physisorption. Metals contents of the samples were also determined by atomic absorption spectrophotometry. Their catalytic performances were evaluated on cyclohexane oxidation using oxygen as oxidant in the absence of solvents and reductants. The supported catalysts have shown high catalytic activities for cyclohexane oxidation. Especially, when 5% loading of CoFe2O4/SiO2 was employed, 4181 turnover number and 95.4% selectivity for cyclohexanone and cyclohexanol were obtained under 1.6 MPa of initial oxygen pressure at 418 K after 6.0 h of reaction. The sample of 50% of CoFe2O4/SiO2 has strong magnetism and can be magnetically separated easily. This sample was employed as catalyst to optimize the reaction conditions. The catalyst showed prominent reusability, and no obvious loss in activity was observed when reused in six consecutive runs.

•Eggshell membranes were used as biological nitrogen and carbon source.•The process is an environmentally friendly one, which turns waste into treasure.•The catalyst exhibits superior electrocatalytic activity compared with commercial Pt/C (20%).Composite of FeCo alloy embedded in nitrogen self-doped biocarbon was faciely prepared by pyrolysis of precursor of eggshell membrane mixed with nitrates. Three samples were prepared at different pyrolysis temperatures and well characterized by transmission electron microscopy (TEM), Raman spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption analysis. The as-prepared samples exhibit high electrocatalytic activities toward oxygen reduction reaction under alkaline conditions. Especially, the sample pyrolyzed at 800 °C exhibits superior electrocatalytic activity, stability and resistence for methanol corrosion compared with commercial Pt/C (20%) and exhibit a four-electron ORR pathway in alkaline condition. The catalyst also exhibits brilliant capacity of supercapacitor.Download high-res image (177KB)Download full-size image

H3+xPMo12−xVxO40@MIL-100 (Fe) (x = 0, 1, 2) hybrids were prepared by encapsulation of polyoxometalates (POMs) within a metal–organic framework using a direct hydrothermal method. The as-prepared samples were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), transmission electron microscopy (TEM), N2 adsorption–desorption, UV-vis diffused reflectance spectra and inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis. The catalytic performances of the samples were tested in the oxidation of cyclohexene using H2O2 as green oxidant. The results have shown that both H4PMo11VO40@MIL-100 (Fe) and H5PMo10V2O40@MIL-100 (Fe) can effectively catalyze the allylic oxidation of cyclohexene to give 2-cyclohexen-1-one as the main product. In particular, when H4PMo11VO40@MIL-100 (Fe) was employed, 85% cyclohexene conversion, 91% selectivity for 2-cyclohexene-1-one and 715 h−1 of turnover frequency were obtained under optimized conditions. The catalyst can be reused at least five times without obvious loss of activity.

A series of hybrid materials ([C4mim]3+xPMo12−xVxO40, x = 0, 1, 2) based on V-substituted phosphomolybdic acid H3+xPMo12−xVxO40 (x = 0, 1, 2) and ionic liquid 1-butyl-3-methyl imidazolium bromide ([C4mim]Br) have been prepared by anion-exchange method. The samples were well characterized by X-ray diffraction, Fourier transform infrared spectrophotometry and UV–Vis diffuse reflectance spectra analysis. The catalytic performances of the samples were tested in oxidation of benzyl alcohol to produce benzaldehyde using H2O2 as oxidant in water. The results have shown that the hybrids [C4mim]3+xPMo12−xVxO40 exhibit much higher catalytic properties than both the corresponding moieties. Especially, under the optimized conditions, 34% of benzyl alcohol conversion and 99% of selectivity for benzaldehyde have been obtained in the case of [C4mim]4PMo11VO40. The sample also exhibits good reusability and has been reused five runs without much decrease in conversion and selectivity.The polyoxometalate/ionic liquid hybrids with greatly enhanced catalytic performances have been synthesized. Benzyl alcohol can be almost quantitatively converted to benzaldehyde. The catalytic system is green and effective.

Magnetic ferrite CoxNi1−xFe2O4 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) nanocrystalline complex oxides were prepared by sol–gel auto-combustion method and well characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance UV–visible spectroscopy and N2 adsorption–desorption analysis. The catalytic performances of the as-prepared samples were evaluated in photocatalytic oxidation of benzyl alcohol using molecular oxygen as oxidant under visible light irradiation. The results have shown that the catalysts exhibit remarkably high activities in the photocatalytic oxidation of benzyl alcohol. In particular, 18.9 % of benzyl alcohol conversion and 90.1 % of selectivity for benzaldehyde were obtained when the sample Co0.3Ni0.7Fe2O4 was used as catalyst under optimum conditions. The catalyst could be magnetically separated easily for reuse, and no obvious loss of activity was observed when reused in six consecutive runs.

Magnetic ferrite Mg1−xCuxFe2O4 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) nanocrystalline complex oxides were prepared by sol–gel auto-combustion method, and characterized by X-ray diffractometry, Fourier transform infrared spectrophotometry, Raman spectrometry, scanning electron microscopy and transmission electron microscopy. Their catalytic performances were evaluated in oxidation of styrene in water using hydrogen peroxide (30 %) as oxidant. The samples were found to be efficient catalysts for the oxidation of styrene to benzaldehyde. Especially, when Mg0.5Cu0.5Fe2O4 was used as catalyst, 21.8 % of styrene conversion and 83.9 % of selectivity for benzaldehyde were obtained at 80 °C for 9 h reaction. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in five consecutive runs.

•The catalyst has been proved much more efficient for cyclohexene oxidation.•The preparation method is simple and economical.•The catalyst can be easily separated by external magnetic field and has exhibited excellent reusability.•The catalytic system is environmentally friendly.Five magnetic core–shell type Fe3O4@chitosan-Schiff base Co(II), Cu(II) and Mn(II) complexes were prepared in a simple way and well characterized by Fourier transform infrared spectrophotometry (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermogravimetry (TG). Their abilities to catalyze oxidation of cyclohexene with molecular oxygen in the absence of any solvents or reducing agents were investigated. It has been revealed that the as-prepared samples have high catalytic activities for heterogeneously aerobic oxidation of cyclohexene and 2-cyclohexene-1-one is the main product in all cases. Especially, when the Schiff base Co(II) complex derived from 5-nitrosalicyaldehyde was employed as catalyst, 46.8% of cyclohexene conversion, 77.2% of selectivity for 2-cyclohexene-1-one and as high as 4.7 × 103 of turnover number were obtained under ambient pressure at 70 °C for 12 h of reaction. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in five consecutive runs.Five magnetic core–shell type Fe3O4@chitosan-Schiff base Co(II), Cu(II) and Mn(II) complexes were prepared in a simple way. Their abilities to catalyze oxidation of cyclohexene with molecular oxygen in the absence of any solvents or reducing agents were investigated. It has been revealed that the as-prepared samples have high catalytic activities for heterogeneously aerobic oxidation of cyclohexene and 2-cyclohexene-1-one is the main product in all cases. Especially, when the Schiff base Co(II) complex derived from 5-nitrosalicyaldehyde was employed as catalyst, 46.8% of cyclohexene conversion, 77.2% of selectivity for 2-cyclohexene-1-one and as high as 4.7 × 103 of turnover number were obtained under ambient pressure at 70 °C for 12 h of reaction. The catalyst can be magnetically separated easily for reuse and no obvious loss of activity was observed when reused in five consecutive runs.

•Ce-doped cobalt ferrites were prepared by a facile, mild, and green route.•The samples show high activity in styrene oxidation using H2O2 as a green oxidant.•The Ce-doped samples show greatly enhanced performance over the pristine CoFe2O4.•The catalysts can be magnetically separated easily and have prominent recyclability.The rare earth metal Ce-doped cobalt ferrite samples CexCo1−xFe2O4 (x = 0.1, 0.3, 0.5) were prepared by the sol–gel autocombustion route. The as-prepared samples were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, ICP–atomic emission spectroscopy, and N2 physisorption. Their catalytic performance was evaluated in oxidation of styrene using hydrogen peroxide (30%) as oxidant. Compared with pristine CoFe2O4, the Ce-doped samples were found to be more efficient catalysts for the oxidation of styrene to benzaldehyde, with greatly enhanced catalytic performance. Especially, when Ce0.3Co0.7Fe2O4 was used as catalyst, 90.3% styrene conversion and 91.5% selectivity for benzaldehyde were obtained at 90 °C for 9 h reaction. The catalyst can be magnetically separated easily for reuse, and no obvious loss of activity was observed when it was reused in five consecutive runs.Download high-res image (87KB)Download full-size image

H3+xPMo12−xVxO40@MIL-100 (Fe) (x = 0, 1, 2) hybrids were prepared by encapsulation of polyoxometalates (POMs) within a metal–organic framework using a direct hydrothermal method. The as-prepared samples were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), transmission electron microscopy (TEM), N2 adsorption–desorption, UV-vis diffused reflectance spectra and inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis. The catalytic performances of the samples were tested in the oxidation of cyclohexene using H2O2 as green oxidant. The results have shown that both H4PMo11VO40@MIL-100 (Fe) and H5PMo10V2O40@MIL-100 (Fe) can effectively catalyze the allylic oxidation of cyclohexene to give 2-cyclohexen-1-one as the main product. In particular, when H4PMo11VO40@MIL-100 (Fe) was employed, 85% cyclohexene conversion, 91% selectivity for 2-cyclohexene-1-one and 715 h−1 of turnover frequency were obtained under optimized conditions. The catalyst can be reused at least five times without obvious loss of activity.