Shenglian Luo

Synthesis and structure of an air-stable cationic organobismuth complex and its use as a highly efficient catalyst for the direct diastereoselective Mannich reaction in water

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

Hollow peanut-like m-BiVO4: facile synthesis and solar-light-induced photocatalytic property

Monoclinic bismuth vanadate (m-BiVO4) with novel hollow peanut-like morphology was synthesized for the first time using L-lysine as surfactant. The use of L-lysine and the crystallization procedure is indispensable in getting the peanut-like morphology. The photocatalytic activity of the m-BiVO4 samples under solar-light irradiation was evaluated for degradation of crystal violet and methylene blue. Crystallization and calcination temperature are important factors affecting the photocatalytic activity of m-BiVO4, and best performance was observed over the sample that crystallized at 160 °C in the presence of L-lysine and subsequently subjected to calcination at 550 °C. The as-prepared BiVO4 showed good stability in catalyst recycling. Based on the results of XRD, XPS, FESEM, TEM (HRTEM), UV-vis diffuse reflectance spectroscopy, and N2 adsorption–desorption characterization, the good photocatalytic activity of the m-BiVO4 sample is attributed to its unique hollow peanut-like morphology and pure monoclinic phase of high crystallinity.

Controllable synthesis of hollow and porous Ag/BiVO4 composites with enhanced visible-light photocatalytic performance

By adjusting the amount of AgNO3, hollow and porous silver bismuth vanadate (Ag/BiVO4) composites were synthesized by a one-step method using ethylene glycol and water as solvents, and L-lysine as a surfactant. The as-synthesized samples were characterized by XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS, PL and nitrogen adsorption–desorption techniques. The effect of the amount of AgNO3 on the morphology of the products was investigated and using the right amount of AgNO3 was essential to obtain the hollow and porous structure. A possible mechanism for the growth of the composites was proposed. The photocatalytic performance of the composites was evaluated for the degradation of methylene blue and rhodamine-B in an aqueous solution under visible-light irradiation. The Ag/BiVO4 composites showed excellent photocatalytic activity at a silver content of 6.5 wt%. The 6.5 wt% Ag/BiVO4 catalyst performed better than BiVO4 as well as better than the Ag-doped BiVO4 prepared by a photoreduction method. There is a strong relationship between photocatalytic performance and the structure of catalysts. It was deduced that the excellent photocatalytic activity of 6.5 wt% Ag/BiVO4 is due to its hollow and porous structure, large specific surface area, and Ag/BiVO4 interfaces.

Low-Cost Polymer-Supported Quaternary Ammonium Salts as High-Efficiency Catalysts for Cycloaddition of CO2 to Epoxides

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 (150xa0°C, initial CO2 pressure 2.0xa0MPa and 5xa0h), propylene carbonate yield and selectivity in the cycloaddition of CO2 to propylene oxide over PS-CQNS were 96.2 and 99.3xa0% whereas those over PS-QNS were 97.9 and 99.5xa0%, 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.Graphical AbstractPolystyrene bearing quaternary ammonium salt ionic liquids (denoted as PS-QNS and PS-CQNS) were fabricated and evaluated for solventless synthesis of cyclic carbonates from CO2 and epoxides. The catalysts are low in cost and simple to prepare, and show good activity, selectivity, stability and reusability towards the cycloaddition reaction.

Effect of butterfly-shaped sulfur-bridged ligand and counter anions on the catalytic activity and diastereoselectivity of organobismuth complexes

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.

Facile separation catalyst system: direct diastereoselective synthesis of (E)-α,β-unsaturated ketones catalyzed by an air-stable Lewis acidic/basic bifunctional organobismuth complex in ionic liquids

The catalyst system that comprises an air-stable bifunctional Lewis acidic/basic organobismuth complex and [Bmim]BF4 is highly efficient in the cross-condensation of aldehydes with ketones. Through switching the reaction from homogeneous to heterogeneous, the system shows facile separation ability and facile reusability.

Novel MgO–SnO2 Solid Superbase as a High-Efficiency Catalyst for One-Pot Solvent-Free Synthesis of Polyfunctionalized 4H-pyran Derivatives

We report for the first time the hydrothermal synthesis of MgO–SnO2 solid superbase using P123 as template. The basicity of the materials was determined by two approaches of Hammett indicators method and temperature-programmed desorption using CO2 as adsorbate (CO2-TPD). It was found that Mg/Sn molar ratio has an effect on MgO–SnO2 basicity, and superbasicity was observed only at Mg/Sn molar ratio of 1. With variation of Mg/Sn molar ratio, superbase strength (H-) was in the 26.5–33.0 range, showing superbasic value up to 0.939xa0mmol/g. The structure and texture of the as-prepared materials were studied by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 physio-adsorption methods. We detected particles of spherical morphology having diameter of ca. 150xa0nm. N2 adsorption–desorption results suggested that the materials are of mesoporous structure, having specific surface area of 115.2xa0m2/g and average pore diameter of 6xa0nm. The superbase was found to exhibit excellent catalytic activity towards the one-pot synthesis of polyfunctionalized 4H-pyrans through the condensation of aldehydes, malononitrile, and an active methylene compound. Its excellent catalytic efficiency is related to its superbasicity of the MgO–SnO2. The results provide a new route for the design and preparation of composite oxide superbases. Furthermore, the solid superbases will facilitate a strategy for high-efficiency synthesis of polyfunctionalized 4H-pyrans.Graphical AbstractNovel MgO–SnO2 solid superbase was prepared using P123 as template. Its superbase strength was in the 26.5–33.0 range, showing superbasic sites up to 0.939xa0mmol/g. The material is of mesoporous structure,(having specific surface area of 115.2xa0m2/g and average pore diameter of 6xa0nm. It was found to exhibit excellent catalytic activity towards the one-pot solvent-free synthesis of polyfunctionalized 4H-pyrans through the condensation of aldehydes, malononitrile, and an active methylene compound. The results provide a new route for the design and preparation of composite oxide superbases.

Influences of solution pH and redox potential on the bioleaching of LiCoO2 from spent lithium-ion batteries

The influences of solution pH and redox potential on bioleaching of LiCoO2 from spent lithium-ion batteries using Acidithiobacillus ferrooxidans were investigated. Bioleaching at different initial pH and ferrous ion (Fe2+) concentrations were carried out, and electrochemical behavior of LiCoO2 dissolution was examined to study the effect of solution redox potential on the bioleaching process. The results showed maximum cobalt dissolution at initial pH of 1.5 and initial Fe2+ concentration of 35 g/L, and cobalt dissolution showed only slight relationship with pH of solution. Nonetheless, there was improvement of cobalt dissolution at higher redox potential. The cyclic voltammograms showed that dissolution rates increase when the solution potentials are higher than 0.4 V, and rapid decrease at 1.3 V. The anodic polarization curves indicated that the corrosion, primary passive, and passivation potentials were 0.420, 0.776 and 0.802 V, respectively.