The Co3O4 catalysts with regular cubes in shape were prepared by direct hydrothermal synthesis with the assistance of a triblock copolymer (P123). The synthesized materials were characterized by powder X-ray diffraction, scanning electron microscopy, and nitrogen adsorption–desorption techniques. It was found that the Co3O4 catalysts showed high catalytic activity and selectivity for the Baeyer–Villiger oxidation of cyclic ketones in the presence of 1,2-dichloroethane and dioxygen. The effects of reaction conditions (catalyst amount, reaction temperature, reaction time, and different solvents) on the catalytic performance of Co3O4 were investigated. It was observed that under optimal reaction conditions, cyclohexanone conversion and ε-caprolactone selectivity could reach 98 and 100 %, respectively. In addition, the process has advantages such as mild reaction conditions, simple operation, and high product yield. Furthermore, the catalyst can be reused for several times without obvious loss of activity and selectivity.

Polystyrene grafted with quaternary ammonium salts were obtained by direct quaternarization of chloromethylated polystyrene with N,N-dimethylethylamine, N,N-dimethylglycine (denoted as PS-QNS and PS-CQNS, respectively). These two polymer-supported ionic liquids were found to show high catalytic efficiency towards the cycloaddition of CO2 to epoxides. The effects of catalyst amount, reaction temperature, initial CO2 pressure, and reaction time on the yield of cyclic carbonates were investigated systematically. Under the optimal reaction conditions (150 °C, initial CO2 pressure 2.0 MPa and 5 h), propylene carbonate yield and selectivity in the cycloaddition of CO2 to propylene oxide over PS-CQNS were 96.2 and 99.3 % whereas those over PS-QNS were 97.9 and 99.5 %, respectively. It was observed that the reusability of PS-QNS was excellent. From the viewpoint of industrial application, PS-QNS is attractive in terms of catalytic efficiency, cost and simplicity in preparation.

Here we report the in vitrobiomineralization of SrCO3 complex nanostructures obtained using glucosan as the modifier in dimethyl formamide (DMF)–deionized water (DIW) mixed solvents. Rod-, dendrite-, dumbbell-, and sphere-like SrCO3 nanostructures were achieved by tuning the volume ratios of DMF/DIW, reaction time, and concentrations. The phase, structure, and morphology of the as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The possible formation mechanism of SrCO3 complex nanostructures follows the rod–dumbbell–sphere growth process. The as-synthesized SrCO3 complex nanostructures show excellent adsorption properties and superhydrophobicity, which may open up a wide range of potential applications in environmental protection.

In the direct Mannich reaction and synthesis of α,β-unsaturated ketones, the use of organobismuth complexes as catalysts leads to high diastereoselectivity and products of single trans conformation. In this paper, we illustrate the relationship between structure and catalytic activity as well as diastereoselectivity of organobismuth complexes having a 5,6,7,12-tetrahydrodibenz [c,f][1,5]thiobismocine framework as well as bearing a butterfly-shaped sulfur-bridged ligand and tunable anions. With the exposed bismuth center acting as a Lewis acid site and the uncoordinated lone pair electrons of sulfur as a Lewis base site, the cationic organobismuth complexes work as bifunctional Lewis acid/base catalysts. Due to the steric influence of the butterfly-shaped structure and synergistic effect of Lewis acid and Lewis base centers, the complexes can direct substrate attack in organic synthesis. By adjusting the electron-withdrawing ability of the counter anions, the S–Bi bond strength can be regulated, leading to a significant change in Lewis acidity and Lewis basicity as well as catalytic activity. Through synergistic modulation of the above effects, one can control the diastereoselectivity of the organobismuth complexes for the generation of a single diastereoisomer.

A series of Bi2O3–MgO composites were synthesized by solvent-thermal method. It was found that the Bi2O3–MgO composites perform much better than TiO2 (P25), Bi2O3 and MgO in the photocatalytic degradation of rhodamine B (RhB) in the presence of HCl and under irradiation of visible light (λ > 400 nm). The effects of Bi/Mg molar ratio, crystallization temperature of Bi2O3–MgO and reaction conditions on photocatalytic activity were studied. The best performance was observed over the composite with Bi:Mg molar ratio equal to 2:1 that had been subject to crystallization at 120 °C for 20 h. In addition, the photocatalytic efficiency of the composite can be significantly enhanced by the presence of hydrochloric acid. The prepared samples were characterized by XRD and UV–vis DRS techniques. The relationships between the structure and photocatalytic performance of the as-prepared Bi2O3–MgO samples were also investigated.

Described in this paper are the synthesis, characterization and catalytic application of H-ZSM-5 zeolites for the conversion of CH3Br into aromatics. The H-ZSM-5 zeolites were fabricated by hydrothermal crystallization using n-butylamine (BTA) as a template and characterized by XRD, SEM and NH3-TPD techniques. The effects of batch SiO2/Al2O3 ratio, alkalinity, NaCl/Al2O3 ratio, seed crystals, and crystallization time on the yield, structure/texture and catalytic performance were systematically studied. Adopting the optimum sol (SiO2/Al2O3 = 70, BTA/SiO2 = 0.2847, Na2O/SiO2 = 0.1237, H2O/SiO2 = 37.4, NaCl/Al2O3 = 60, and seed/SiO2 = 5 wt%) and under the most preferable crystallization conditions of 100 °C/24 h–170 °C/24 h, H-ZSM-5 zeolites of high crystallinity and small size (300–700 nm) were obtained. Good catalytic performance was observed over the H-ZSM-5 zeolites (aromatic yield up to 44.2%). However, unlike the modification of large commercial HZSM-5, the use of MoO3 or PbO as modifying agents for the small-size H-ZSM-5 zeolites results in a decline of catalytic performance. The relationship between the structure and the catalytic efficiency of as-synthesized H-ZSM-5 samples were investigated. It was found that with crystallinity enhancement and/or decline in crystal size, there is improvement of catalytic performance.

Air-stable hypervalent organobismuth(III) tetrafluoroborate (C6H11N(CH2C6H4)2BiBF4) was synthesized and characterized by spectroscopic and X-ray crystallographic techniques. The compound shows good catalytic efficiency in the allylation reaction of different aldehydes with tetraallyltin in a medium of aqueous methanol, giving the corresponding homoallylic alcohols in excellent chemoselectivity and yields.The allylation of different aldehydes with tetraallyltin was successfully operated over hypervalent organobismuth(III) tetrafluoroborate catalyst in a medium of aqueous methanol, giving the corresponding homoallylic alcohols in excellent chemoselectivity and yields.

Hydroxyl ionic liquid grafted onto cross-linked divinylbenzene polymer (PDVB-HEIMBr) was fabricated and evaluated as a catalyst for the synthesis of cyclic carbonates from CO2 and epoxides without the use of any co-catalyst and organic solvent. The catalyst shows good performance across a wide range of epoxides, giving almost quantitative yield of carbonates (140 °C, 2.0 MPa of initial CO2, and ≤4 h). The effects of reaction temperature, time and initial CO2 pressure on product yield were investigated. It is suggested that the synergetic effect between the bromide ions and the hydroxyl groups facilitates the coupling reaction. Furthermore, the PDVB-HEIMBr catalyst shows excellent stability and reusability. From the viewpoint of industrial application, the catalyst is very attractive because of its simplicity, activity, stability, and reusability.

A series of Zn-Al composite oxides that were modified with alkaline earth metals, Zn-M-Al-O (M = Mg, Ca, Sr, and Ba) were fabricated via calcination of the corresponding hydrotalcite precursors, and evaluated as catalysts for the synthesis of propylene carbonate (PC) from CO2 and propylene oxide. Among the Zn-M-Al-O catalysts, Zn-Mg-Al-O (Zn/Mg = 4.0, pH = 10, without hydrothermal treatment) is the best in performance, showing PC selectivity of 99.2% and yield of 88.8% (140 °C, 12 h). Furthermore, the Zn-Mg-Al-O catalyst can be readily reused and recycled without any loss of activity in a test of five cycles. Through detailed studies of the basic nature of the Zn-M-Al-O catalysts, it was found that a moderate basicity (6.1 ≤ H0 < 8.9) is beneficial to the cycloaddition reaction. The NH3- and CO2-TPD results also indicate that the Zn-Mg-Al-O catalyst has acid–base bifunctional properties, and a reaction mechanism is proposed.

Air-stable Lewis acidic μ2-hydroxy bridged binuclear complex of zirconocene pentafluorophenylsulfonate was successfully synthesized and found to show high catalytic efficiency in chemoselective allylation of carbonyl compounds with tetraallyltin in aqueous methanol media.

An air-stable cationic organobismuth complex was successfully synthesized and found to show high catalytic efficiency in the direct diastereoselective Mannich reaction in water.

A solid superbase with H_ above 26.5 has been obtained through thermal treatment of sodium stannate hydrate. It was found to be an efficient catalyst for anti-Markovnikov hydroamination and hydroalkoxylation of electron-deficient olefins under mild conditions.A novel solid superbase with basic strength (H_) above 26.5 was obtained through calcination of sodium stannate hydrate. It was found to show high catalytic efficiency towards the anti-Markovnikov hydroamination and hydroalkoxylation of electron-deficient olefins under mild conditions.Download full-size imageResearch Highlights► The calcined sodium stannate was found to show superbasicity. ► The process for the generation of the superbase is of low energy consumption. ► The as-prepared material shows high catalytic efficiency under mild conditions. ► The catalyst exhibits good thermal stability and recyclability.

We report for the first time the synthesis of a novel solid superbase that was derived from lanthanum–magnesium composite oxide and KOH through thermal treatment. The as-prepared material shows base strength (H–) above 26.5 and is a high-efficiency catalyst for solvent-free Knoevenagel condensation at room temperature. The results of the present study open up a new dimension for the use of composite oxides as new support materials in the synthesis of superbases.Highlights► The solid superbase using Mg-La composite oxide as support has been obtained. ► It exhibits high catalytic efficiency in solvent-free Knoevenagel condensation at RT. ► The catalytic performance depends on the strength and the amount of superbasic sites.

Here we report the in vitrobiomineralization of SrCO3 complex nanostructures obtained using glucosan as the modifier in dimethyl formamide (DMF)–deionized water (DIW) mixed solvents. Rod-, dendrite-, dumbbell-, and sphere-like SrCO3 nanostructures were achieved by tuning the volume ratios of DMF/DIW, reaction time, and concentrations. The phase, structure, and morphology of the as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The possible formation mechanism of SrCO3 complex nanostructures follows the rod–dumbbell–sphere growth process. The as-synthesized SrCO3 complex nanostructures show excellent adsorption properties and superhydrophobicity, which may open up a wide range of potential applications in environmental protection.

In the direct Mannich reaction and synthesis of α,β-unsaturated ketones, the use of organobismuth complexes as catalysts leads to high diastereoselectivity and products of single trans conformation. In this paper, we illustrate the relationship between structure and catalytic activity as well as diastereoselectivity of organobismuth complexes having a 5,6,7,12-tetrahydrodibenz [c,f][1,5]thiobismocine framework as well as bearing a butterfly-shaped sulfur-bridged ligand and tunable anions. With the exposed bismuth center acting as a Lewis acid site and the uncoordinated lone pair electrons of sulfur as a Lewis base site, the cationic organobismuth complexes work as bifunctional Lewis acid/base catalysts. Due to the steric influence of the butterfly-shaped structure and synergistic effect of Lewis acid and Lewis base centers, the complexes can direct substrate attack in organic synthesis. By adjusting the electron-withdrawing ability of the counter anions, the S–Bi bond strength can be regulated, leading to a significant change in Lewis acidity and Lewis basicity as well as catalytic activity. Through synergistic modulation of the above effects, one can control the diastereoselectivity of the organobismuth complexes for the generation of a single diastereoisomer.

Air-stable Lewis acidic μ2-hydroxy bridged binuclear complex of zirconocene pentafluorophenylsulfonate was successfully synthesized and found to show high catalytic efficiency in chemoselective allylation of carbonyl compounds with tetraallyltin in aqueous methanol media.