Jianzhang Li

Synthesis and Study of Unsymmetrical Schiff Base Mn(III) Complexes with Pendant Aza-crown or Morpholino Groups as Catalyst in Aerobic Oxidation for p-Xylene to p-Toluic Acid

A series of novel unsymmetrical Schiff base Mn(III) complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of `p-xylene to p-toluic acid (PTA). The oxidation of p-xylene to p-toluic acid with air at 120°C under normal atmospheric pressure occurred efficiently in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(III) complexes. Significant selectivity (up to ∼90%) and conversion levels (up to ∼40%) were obtained. The effect of the aza-crown ring appended in Mn(III) Schiff base complexes on the oxidation of p-xylene were also investigated by comparison with the morpholino group pendant analogues. The addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.

Enhanced separation efficiency of photo-induced charge pairs and sunlight-driven photocatalytic performance of TiO 2 prepared with the assistance of NH 4 Cl

The photocatalytic performance of TiO2 is significantly limited by its high recombination rate of photo-generated charge carriers, and therefore it is essential to further boost the photocatalytic activity of TiO2. In this paper, to enhance the separation efficiency of the photo-generated charge carriers by surface state regulation, a series of TiO2 photocatalysts were prepared by sol–gel method with the assistance of NH4Cl and studied by the Brunauer-Emmet Teller method, X-ray diffraction patterns, UV-VIS diffuse reflectance spectra, scanning electron microscopy with energy dispersive spectroscopy and surface photovoltage spectroscopy. The relative amount of •O2− was measured using nitrotetrazolium blue chloride (NBT) method. The photocatalytic activities of the samples under the simulated sunlight irradiation were investigated using Rhodamine B as the model dye. The results reveal that all the samples prepared with the assistance of NH4Cl display better photocatalytic activity than the reference TiO2 and the enhancement mechanism was proposed.Graphical abstract

Enhanced Hydrolysis of p-Nitrophenyl Picolinate by Schiff Base Mn(III) Complexes in Gemini 16-6-16 Micelles

Hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by three Schiff base Mn(III) complexes (MnL2Cl) were investigated in Gemini 16-6-16 micelle media. , and systems give 835-, 969-, and 1931-fold rate enhancements in the hydrolysis of PNPP under the comparable conditions, respectively. Moreover, Effects of varied micelles on the reactivity of PNPP hydrolysis were especially studied. The results obtained indicate that rates of hydrolysis of PNPP are approximately 1.5- and 4-fold larger in Gemini 16-6-16 micelles than in CTAB micelles and Brij35 micelles, respectively. Effects of ligand structure on the activities of these three complexes are discussed in detail.

Studies on p -nitrophenyl Picolinate Cleavage by Unsymmetrical bis-schiff base Complexes with aza-crown ether or Morpholino Pendants

The unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL1Cl, CoL1, CoL2) or a morpholino pendant (MnL3Cl) have been demonstrated as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH. The complexes of ligands containing a crown ether group exhibit higher catalytic activities than the non-crown analogue; the catalytic activity of the complexes follows the order Mn(III) > Co(II) (MnL1Cl > CoL1) with the same ligands.

Hydrolysis of BNPP Catalyzed by the Crowned Schiff Base Co(II) Complexes in Micellar Solution

Two symmetrical double aza‐crowned Schiff base cobalt(II) complexes were synthesized and characterized, and the metallomicelle made up of the cobalt(II) complexes and surfactant, as mimic hydrolytic metalloenzyme, was used in catalytic hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and Co(II) complexes are formed in reaction processes of the BNPP catalytic hydrolysis. In this article, the mechanism of BNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, for the calculation of the kinetic parameter of BNPP catalytic hydrolysis has been established based on the mechanism proposed. The acid effect of reaction system, the structural effect of the complexes, the effect of surfactant micelles and the effect of temperature on the rate of BNPP hydrolysis catalyzed by the complexes have been discussed.

Bovine serum albumin modified ZnO to degrade organic dyes under ultraviolet light irradiation

Bovine serum albumin (BSA), a non-toxic natural polymer material, is used as a template agent to modify the as-prepared photocatalyst ZnO, changing the ZnO nanorod into a nanosheet. The synthesized samples were characterized by scanning microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR) spectroscopy, photoluminescence (PL) spectroscopy and the Brunauer–Emmett–Teller method (BET). The photocatalytic performance of the samples was evaluated via the photocatalytic degradation process of methylene blue (MB) and phenol under UV-light irradiation. Compared to pure ZnO, the ZnO/BSA composites exhibited superior photocatalytic activity, which could be attributed to the distensible surface area and the effective separation of photoinduced electron–hole pairs. Besides, the BSA used as a template could promote the photocatalysts to absorb more dye particles on its surface and improve degradation performance, which could be applied in a similar fashion between the protein and MB.

Fabrication of Dy-doped BiVO4 with Enhanced Solar Light Photocatalytic Performance

BiVO4 and Dy-doped BiVO4 photocatalysts with different molar ratio of Dy/Bi (1%, 2%, 3%, and 4%) were prepared by a sol–gel method and characterized by Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV/Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopic (XPS) techniques, and surface photovoltage spectroscopy (SPS), respectively. The photocatalytic performance for decolorization of rhodamine B (RhB) aqueous solution under solar light was evaluated, the results show that Dy-doped BiVO4 with about 2%Dy possesses the best photocatalytic activity and the underlying mechanism is suggested.

Studies on the Phenol Oxidation with H2O2 Catalyzed by Metallomicelle Made from Crowned Schiff Base Mn(III) Complexes

Metallomicelles made from two Schiff base manganese(III) complexes (MnL1 and MnL2) and surfactants (CTAB and Brij35) were used as mimetic peroxidase in the catalytic oxidation of phenol by H2O2. The catalytic activity of the complexes (MnL1 and MnL2) were investigated. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were also studied. The results show the optimum acidity of the enzyme-like system in the paper is ca. pH 7.0, the optimum temperature which is ca. 35°C and the optimum molar ratio of H2O2 to the complex is ca. 30 in the complexes-H2O2-buffered solution; the Schiff base manganese(III) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.

Studies on Phenol Oxidation with H2O2 Catalyzed by Schiff Base Cobalt(II) Complexes in Micellar Solution

The two Schiff base cobalt(II) complexes, CoL1 and CoL2, were synthesized and characterized. The metallomicelle made up of the cobalt(II) complexes and surfactants (CTAB, LSS and Brij35), as mimic peroxidase metalloenzyme, were used in the catalytic oxidation of phenol by H2O2. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were studied. The acid effect of reaction system, structural effect of the complexes, and effect of temperature on the rate of the phenol oxidation catalyzed by the mimetic peroxidases have been discussed. The results showed that the schiff base cobalt(II) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.

A flower-like TiO2 with photocatalytic hydrogen evolution activity modified by Zn(II) porphyrin photocatalysts

The Zn(II)5,10,15,20-tetrakis [m-methoxy-p-hydroxyl-phenyl] porphyrins (ZnTmMpHPP) as a photosensitizer was applied to modified TiO2 and the composite was prepared via a hydrothermal process. The as-obtained flower-like TiO2 and TiO2/ZnTmMpHPP composites were characterized by X-ray diffractometry, scanning electron microscopy, Fourier transform infared spectromotry, transient photocurrent responses and BET. Photocatalytic hydrogen production results show the TiO2/ZnTmMpHPP composite has a higher photocatalytic activity than pure TiO2 under ultraviolet light irradiation, which is due to the enhanced transfer and separation efficiency of photo-induced carriers from the ZnTmMpHPP to TiO2 with the help of conjugated π bond in ZnTmMpHPP. The recycled H2 evolution test indicates that the TiO2/ZnTmMpHPP composite is stable enough under the reaction system. In the presented paper, it is proven that the ZnTmMpHPP can greatly accelerate the separation of charges and effectively improve the photocatalytic H2 evolution activity of TiO2.