Tuning the Optoelectronic Properties of Hybrid Functionalized MIL-125-NH2 for Photocatalytic Hydrogen Evolution.

Metal-organic frameworks (MOFs) constructed with mixed ligands have shown great promise in the generation of materials with improved sorption, optical, and electronic properties. With an experimental, spectroscopic, and computational approach, herein, we investigated how the incorporation of different functionalized ligands within the structure of MIL-125-NH2 affects its performance in photocatalytic water reduction. We found that multiligand incorporation within the MOF structure has an impact on the light absorption spectrum and the electronic structure. These combined modifications improve the photocatalytic performance of MIL-125-NH2, thereby increasing the rate of hydrogen evolution reaction. Of the four nanoparticle/MOF photocatalytic systems tested, we showed that the Pt/MIL-125-NH2/(OH)2 system (Pt nanoparticle plus MIL-125-NH2 with amino and dihydroxyl functionalized ligands) outperforms its counterpart Pt/MIL-125-NH2 system, attributed to the enhanced p-π conjugation between the lone pairs of O atoms and their aromatic ligands resulting in a red-shifted absorption spectrum and greater spatial distribution of electron density.

A novel L-Histidine (C, N) codoped-TiO2-CdS nanocomposite for efficient visible photo-degradation of recalcitrant compounds from wastewater.

The aim of current study is to synthesis novel visible driven photocatalysts (L-Histidine (C, N) codoped-TiO2-CdS) with different loadings of L-Hisitdine (1, 2, and 3 wt.%) and CdS (1:9, 7:1, and 1:5 mass ratios of CdS to TiO2). Then, their application for photo-degradation of methyl orange (MO) and biologically treated palm oil mill effluent (POME) were studied. The structure, optical properties, and morphology of the prepared nanocomposites were also characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), photoluminescence spectroscopy (PL), and diffuse reflectance spectra (DRS). DRS results indicated that all the modified samples with different L-Hisitdine and CdS loadings showed a red shift to visible region. The results of photo-degradation experiments showed that L-Hisitdine with a weight fraction of 2% and mass ratio of TiO2 to CdS of 7:1 were the optimum amount of the modifiers in the photocatalyst network. The PL intensity of the photocatalyst decreased with addition of L-Hisitdine and CdS nanoparticles due to a decrease in e-/h+ recombination. The effects of organic pollutant concentration, initial pH, catalyst concentration, and irradiation time on the photo-degradation process of MO and POME were studied using full faced centered central composite design (CCFD) under response surface methodology (RSM). The obtained results showed that MO was completely removed at initial concentration of 10 mg/L, acidic pH, and catalyst loading of 1.5 g/L after 120 min. The complete degradation of biologically treated POME was achieved at original pH, 300 mg/L of chemical oxygen demand (COD) concentration, catalyst loading of 2 g/L, and irradiation time of 2 h.

Synthesis of Fe-Cu/TiO2 nanostructure and its use in construction of a sensitive and selective sensor for metformin determination.

A carbon paste electrode modified with Fe-Cu/TiO2 was prepared and used for low level determination of metformin (MET) using square wave adsorptive stripping voltammetry (SWAdSV). The Fe-Cu/TiO2 nanoparticle was synthesized by a modified sol-gel method. The surface structure and composition of nanoparticles were characterized by scanning electron microscopy (SEM), X-ray powder diffraction analysis (XRD) and N2 physisorption. Also, electrochemical properties of the prepared nanocomposite modified electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques. Under optimized conditions, the modified electrode exhibited a linear response over the concentration range of 15 nM to 75 µM MET, with a detection limit of 3 nM. The proposed sensor exhibited a high sensitivity, good selectivity and was successfully applied for MET determination in real samples such as human urine and pharmaceutical formulations.

Kinetic study on the Cs(x)H(3-x)PW12O40/Fe-SiO2 nanocatalyst for biodiesel production.

The kinetic of the transesterification reaction over the Cs(x)H(3-x)PW12O40/Fe-SiO2 catalyst prepared using sol-gel and impregnation procedures was investigated in different operational conditions. Experimental conditions were varied as follows: reaction temperature 323-333 K, methanol/oil molar ratio = 12/1, and the reaction time 0-240 min. The H3PW12O40 heteropolyacid has recently attracted significant attention due to its potential for application in the production of biodiesel, in either homogeneous or heterogeneous catalytic conditions. Although fatty acids esterification reaction has been known for some time, data is still scarce regarding kinetic and thermodynamic parameters, especially when catalyzed by nonconventional compounds such as H3PW12O40. Herein, a kinetic study utilizing Gc-Mas in situ allows for evaluating the effects of operation conditions on reaction rate and determining the activation energy along with thermodynamic constants including ΔG, ΔS, and ΔH. It indicated that the Cs(x)H(3-x)PW12O40/Fe-SiO2 magnetic nanocatalyst can be easily recycled with a little loss by magnetic field and can maintain higher catalytic activity and higher recovery even after being used 5 times. Characterization of catalyst was carried out by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), N2 adsorption-desorption measurements methods, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC).