A novel magnetically recoverable thioporphyrazine catalyst (CoPz(S-Bu)8/SiO2@Fe3O4) was prepared by immobilization of the cobalt octkis(butylthio) porphyrazine complex (CoPz(S-Bu)8) on silica-coated magnetic nanospheres (SiO2@Fe3O4). The composite CoPz(S-Bu)8/SiO2@Fe3O4 appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide (H2O2) as oxidant under Xe-lamp irradiation, with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number (TON) of 61.7 at ambient temperature. The biomimetic catalyst CoPz(S-Bu)8 was supported on the magnetic carrier SiO2@Fe3O4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz(S-Bu)8 can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications.Download high-res image (52KB)Download full-size image

In this study, we have successfully prepared a heterogeneous catalyst (K-10 clay-Mo) by the immobilization of bis(acetylacetonato) dioxo-molybdenum(VI) [MoO2(acac)2] on montmorillonite K-10 clay. The structure of the resultant catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electronic microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The catalytic activity of K-10 clay-Mo was tested in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). Although a molecule of HMF contains one hydroxyl group and one aldehyde group, to our surprise, the catalyst showed high catalytic activity for the oxidation of the aldehyde group of HMF into 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). A variety of important reaction parameters such as the reaction temperature, catalyst amount, and solvent were explored. HMFCA could be obtained in a high yield of 86.9% with a HMF conversion of 100% after a short reaction time of 3 h in toluene. More importantly, the catalyst K-10 clay-Mo could be reused several times without a significant loss of its catalytic activity.

•We probe the hydrogen transfer mechanism of H2O and O2 on FeIIPz.•The hydrogen transfer is hindered in the open-shell singlet and quintet states.•The hydrogen transfer becomes easier in the medium spin triplet state.•The water solvent effects favor the hydrogen transfer process.Computational study is performed to probe the hydrogen transfer mechanism of O2 and H2O catalyzed by the Fe(II) porphyrazine on the lowest singlet, triplet and quintet states. Results suggest that Fe(II) prefers to bind H2O with higher adsorption energy than that of O2. The hydrogen transfer from H2O to O2 is hindered by the high energy barrier and reaction heat in the ground singlet and quintet states, which becomes easier in the excited triplet state. Both the explicit and implicit solvent effects of water favor the hydrogen transfer. The energy barriers are linearly correlated with the reaction heats according to the classic Brønsted–Evans–Polanyi relations.Graphical abstract

A novel unsymmetric biomimetic catalyst iron(II) (1,4-dithiin)3-4-pentyloxyphenyl-porphyrazine [abbreviated as FePzPh(1,4-dithiin)3] was successfully synthesized by a template method. Its photocatalytic activity was evaluated by the degradation of rhodamine B under solar-simulating Xe lamp irradiation. A high degradation ratio and TOC removal were achieved in 97.3% and 70%, respectively, at pH 9.18 in 100 min. Wavelength filter experiments demonstrated that the small portion of light with the wavelength shorter than 420 nm played a significant role in the activation of molecule oxygen to degrade RhB. The photocatalytic activity of this unsymmetric catalyst FePzPh(1,4-dithiin)3 is higher than its symmetric matrix. Hydroxyl radicals were detected as a main reactive oxidative species, and a possible mechanism of the activation of molecular oxygen catalyzed by FePzPh(1,4-dithiin)3 was proposed.

Highlights•Production of HMF from sucrose catalyzed by ScCl3 was realized in ionic liquids.•Microwave irradiation not only reduced reaction time, but also increased HMF yield.•Under the optimal conditions, HMF yield in 73.4% from sucrose was achieved in 2 mins.•Catalyst could be recycled several times without losing its activity.In this study, synthesis of HMF from carbohydrates was carried out in ionic liquids 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) catalyzed by ScCl3 under microwave irradiation. Under the optimal reaction conditions, HMF was obtained in a high yield of 73.4% in 2 mins with the microwave power at 400 W. Compared with the conventional oil-bath heating manner, the use of microwave irradiation not only reduced reaction times from hours to minutes, but also improved HMF yield. This catalytic system could be reused several times without losing its catalytic activity. This efficient catalytic system will generate a promising application strategy for biomass transformation.Graphical abstract

A novel photocatalyst iron(II) tetrahydoxymethyl-tetra(1,4-dithiin) porphyrazine (abbreviated as FePz(hmdtn)4) has been successfully synthesized by template method. The prepared FePz(hmdtn)4) was further characterized by UV–vis, FT-IR, 1H NMR, LC–MS, XPS. FePz(hmdtn)4 supported on an Amberlite CG-400 resin was used as a biomimetic catalyst for the activation of molecular oxygen with visible light to degrade a probe dye compound Rhodamine B (RhB) in aqueous solution with the degradation yield in 79% for 24 h. By means of cyclic voltammetry, the EHOMO and the ΔEHOMO–LUMO were obtained by comparing the CV and DPV spectra of the metal-free compound with FePz(hmdtn)4, which indicated the central Fe2+ showed strong electron donating property for activating molecular oxygen to degrade organic pollutants. The electrochemical results were further verified by the quantum chemical DPT calculation.Graphical abstractHighlights► A novel biomimetic catalyst FePz(hmdtn)4 was synthesized by template method. ► FePz(hmdtn)4 was used to activate oxygen for the degradation of Rhodamine B by 79%. ► Fe2+ showed electron donating property to activate oxygen by electrochemical method. ► The results of electrochemical experiments were supported by DPT calculation.

A novel method has been developed for the direct conversion of fructose into 5-(ethoxymethyl)furfural (EMF) catalyzed by an organic–inorganic hybrid solid catalyst [MIMBS]3PW12O40. First, etherification of 5-(hydroxymethyl)furfural (HMF) by ethanol was studied over a series of catalysts, and [MIMBS]3PW12O40 showed the best catalytic activity with an EMF yield of 90.7% at 70 °C. Then the one-pot dehydrative etherification of fructose into EMF was studied. It indicated that a low temperature (70 °C) was not favored for the dehydrative etherification process, and a high temperature (110 °C) was favored to promote side reactions. A high EMF yield of 90.5% was obtained from fructose at 90 °C with 5 mol % catalyst for 24 h. The recycling test demonstrated that [MIMBS]3PW12O40 could be reused several times without losing catalytic activity, with an average EMF yield of approximate 90%. This work provides a meaningful method for the conversion of carbohydrates into fine chemicals and biofuel additives.

Anatase TiO2 nanocrystals with tunable percentage of reactive {0 0 1} facets were rapidly synthesized by a microwave-assisted hydrothermal treatment of the mixed solution of tetrabutyl titanate (20 g), HF solution (3 ml) and additional water (0–21 g) at 200 °C for 30 min. The resulted sample is denoted as Wx, where x represents the volumes of additional water. The photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption–desorption isotherms and X-ray photoelectron spectroscopy. The photocatalytic activity of the photocatalyst was evaluated by degradation of brilliant red X3B (X3B), an anionic dye, and by a photoluminescence technique using coumarin as a probe molecule. With increasing the amount of additional water from 0 to 21 ml, the shapes of TiO2 nanocrystals evolve from nanosheets to truncated octahedral bipyramids, resulting in a steady decrease in the percentage of exposed {0 0 1} facets (from 71% to 23%). The photocatalytic activity of the resulted surface fluorinated TiO2 nanocrystals increases first and then decrease with increase in the amount of water, and W3 sample with exposed 60% of {0 0 1} facets shows the highest photocatalytic activity. However, for the surface clean TiO2 samples by washing with NaOH solution, W9 with 51% of {0 0 1} facets shows the highest photocatalytic activity. Our experimental results reflect that both crystal planes and surface chemistry play very important roles on the photocatalytic activity of anatase TiO2 nanocrystals.Graphical abstractHighlights► High-energy TiO2 nanocrystals were rapidly synthesized at 200 °C for only 30 min. ► The percentage of exposed {0 0 1} facets is tunable. ► Crystal planes and surface chemistry are important on photo-activity of TiO2.

The novel tetra-(1,4-dithiin) metal-free (H2Pz) and metalloporphyrazines (MPz, M = Mg, Fe) bearing peripheral tetrapropyl-bromine derived from 2,3-dicyano-5-propyl-bromine-1,4-dithiin, were synthesized in a multi-step reaction sequence. These complexes were characterized by 1H NMR, IR, UV–vis, GC–MS, XPS and elemental analysis and their UV–vis spectra were discussed in detail. The iron(II) tetra-(1,4dithiin)porphyrazine bearing peripheral tetrapropyl-bromine was supported on an Amberlite CG-400 resin to form a biomimetic catalyst, the ability of which for activating O2 and H2O2 was estimated from the degradation of Rhodamine B (RhB) under visible light irradiation (λ ⩾ 420 nm). More than 70% of the RhB was degraded by O2 in air for 24 h in the solution of pH 9.18 and by H2O2 only for 12 h in the solution of pH 3.0.Fe(II) porphyrazine/resin exhibits good catalytic performance, and photocatalytic degradation of RhB in the presence of Fe(II) porphyrazine/resin was performed at different conditions.

A new metal-organic framework, [Zn5(trencba)2(OH)2Cl2·4H2O] (1) [H3trencba=N,N,N′,N′,N′′,N′′-tris[(4-carboxylate-2-yl)methyl]-tris(2-aminoethyl)amine], constructed from a flexible tripodal ligand based on C3 symmetric tris(2-aminoethyl)amine, has been synthesized hydrothermally and characterized by elemental analysis, IR, TG, XRD and single-crystal X-ray diffraction analysis. Compound 1 contains an unprecedented linear penta-nuclear zinc cluster fragment. Each ligand links four penta-nuclear fragments, and every fragment links eight ligands to generate a three-dimensional non-interpenetrated porous framework. The uncoordinated water molecules were observed trapped in the void pores. Compound 1 represents the first example of (6,8)-connected 3D bi-nodal framework based on a single kind of organic ligand. The photoluminescence measurements showed that complex 1 exhibits relatively stronger blue emissions at room temperature than that of the ligand.The MOF [Zn5(trencba)2(OH)2Cl2·4H2O] (H3trencba=N,N,N′,N′,N′,N′-tris[(4-carboxylate-2-yl)methyl]-tris(2-aminoethyl)amine) reveals a (6,8)-connected bi-nodal three-dimensional porous framework with unprecedented penta-nuclear fragment, which appears to be a good candidate of hybrid inorganic-organic photoactive materials.

In this study, rhodamine B (RhB) in aqueous solution was effectively degraded by an electro-Fenton (E-Fenton) system with a novel oxygen-fed gas diffusion electrode. This electrode was prepared by combining Cu2O nanocubes and multiwall carbon nanotubes with poly tetrafluoroethylene (Cu2O/CNTs/PTFE). The resulting Cu2O nanocubes and Cu2O/CNTs/PTFE composite cathode were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The degradation of RhB in this E-Fenton system reached 80.2% and 89.3% in 120 min at neutral pH and pH 3, respectively. A pseudofirst-order kinetics was observed for the degradation of RhB in this E-Fenton system. We studied the factors affecting the degradation of RhB with Cu2O/CNTs/PTFE composite cathodes in detail, and detected hydrogen peroxide electro-generated through the reduction of O2 adsorbed on the cathode and copper ions produced by the slow leakage of Cu2O nanocubes. Cyclic voltammetry (CV) experiments revealed that a two-electron reversible redox reaction happened on the Cu2O/CNTs/PTFE cathode in this new E-Fenton system. More importantly, we found the Cu2O/CNTs/PTFE cathode was very stable and could be reused without catalytic activity decrease, suggesting its potential in the wastewater treatment.

A novel unsymmetric biomimetic catalyst iron(II) (1,4-dithiin)3-4-pentyloxyphenyl-porphyrazine [abbreviated as FePzPh(1,4-dithiin)3] was successfully synthesized by a template method. Its photocatalytic activity was evaluated by the degradation of rhodamine B under solar-simulating Xe lamp irradiation. A high degradation ratio and TOC removal were achieved in 97.3% and 70%, respectively, at pH 9.18 in 100 min. Wavelength filter experiments demonstrated that the small portion of light with the wavelength shorter than 420 nm played a significant role in the activation of molecule oxygen to degrade RhB. The photocatalytic activity of this unsymmetric catalyst FePzPh(1,4-dithiin)3 is higher than its symmetric matrix. Hydroxyl radicals were detected as a main reactive oxidative species, and a possible mechanism of the activation of molecular oxygen catalyzed by FePzPh(1,4-dithiin)3 was proposed.