Chitosan-Supported Palladium Catalyst. 1. Synthesis Procedure

Five compounds based on [TeMo6O24]6− and [β-Mo8O26]4− anions synthesized by using different symmetrical and asymmetric N-donor ligands

A series of POM-based compounds can be used as amperometric detectors and the compounds based on [β-Mo₈O₂₆]⁴⁻ can not only detect the cation Cr(vi), but also can photocatalytically reduce Cr(vi).

Multifunctional photoelectric sensors and catalysts for CO2RR and Cr(vi) solution based on a series of POM-based materials

A series of POM-based materials can be used as photoelectric sensors and have high catalytic activities for CO₂RR and the reduction of Cr(vi) solution, which are significant for environmental protection and energy shortage.

One-Pot Synthesis of Pd-Based Ternary Pd@CdS@TiO2 Nanoclusters via a Solvothermal Route and Their Catalytic Reduction Efficiency toward Toxic Hexavalent Chromium

In this work, we report the synthesis of Pd-based ternary Pd@CdS@TiO₂ nanocomposites using molecular precursors. This method is facile, less time-consuming, and cost-effective. This catalyst is prepared within 2 h by a solvothermal route using molecular precursors. Information about the phase, morphologies, elemental mapping, and composition of the nanocomposites was obtained using various characterization techniques. The catalytic activity of the as-prepared Pd-based ternary Pd@CdS@TiO₂ nanocomposites exhibits effective reduction efficiency for the conversion of toxic Cr(VI) to Cr(III) using formic acid as a reducing agent within 5-7 min. To the best of our knowledge, this is the first report on Pd-based ternary Pd@CdS@TiO₂ nanocomposites prepared by a solvothermal route and used as catalysts toward the reduction of hexavalent chromium at room temperature.

Novel CuO/chitosan nanocomposite thin film: facile hand-picking recoverable, efficient and reusable heterogeneous photocatalyst

The present work demonstrates a new simple hand-picking technique for the 100% recovery of a CuO nanosphere photocatalyst.

Enhancement of CdO/ZnO/PVC Nanocomposites Behavior on Photo-Catalytic Degradation of Congo-Red Dye under UV Light Irradiation

nanoCdO/ZnO/PVC composite thin films were prepared by simple solution cast method, using tetra hydrofuran as solvent. nanoCdO/ZnO/PVC composite thin films were irradiated by UV light at the range of 365 nm, 312 nm, and 254 nm. The photo-catalytic activity of CdO/ZnO/PVC was examined by photo-catalytic decolourization of congo-red in aqueous solution. nanoCdO/ZnO/PVC composite film exhibited higher photo-catalytic activity under UV light radiation at 365 nm rather than 312 nm & 254 nm. After 90 minutes irradiation by UV light almost 95% congo-red got decolorized. FT-IR studies confirm the complexation behavior of polymer with ZnO and CdO present in the composite.

Use of tyrosyl bolaamphiphile self-assembly as a biochemically reactive support for the creation of palladium catalysts

The self-assembly of tyrosine-containing bolaamphiphile was applied as a catalyst support on which palladium (Pd) catalysts were loaded to exploit the biochemical activity of tyrosine. The bolaamphiphile self-assembled to form spherical structures exposing tyrosine moieties on the surface. The phenyl group of tyrosine was then used to create the Pd catalyst on the spherical self-assembly. Silver (Ag) clusters were decorated on the surface, exploiting the reducing function of the phenyl group. These Ag clusters were further applied to create Pd catalysts through the galvanic replacement reaction in the next step. The produced Pd catalyst showed reliable catalytic activity in decomposing dichromate with a pseudo-first-order reaction rate. The reaction rate constant increased proportionally to the Pd loading on the self-assembly support. In addition, as a solid support, the bolaamphiphile self-assembly made catalyst recovery easy, and the recovered Pd catalysts showed consistent activity after several cycles. The experimental results demonstrated that the bolaamphiphile self-assembly is a promising organic support with biochemical activity for the facile creation of metallic catalysts.

Synthesis of zero-valent copper-chitosan nanocomposites and their application for treatment of hexavalent chromium

This study used ionotropic crosslinking to synthesize chitosan-tripolyphosphate chelating resin beads, which are used to fabricate zero-valent copper-chitosan nanocomposites. The copper nanoparticles were dispersed on chitosan-tripolyphosphate beads, and were thus able to maintain appropriate dispersion and stability, which greatly improves their applicability. The fabrication process contains two steps: using chitosan-tripolyphosphate beads to adsorb Cu(II) ions, followed by chemical reduction to reduce Cu(II) ions to zero-valent copper. This study explored the adsorption of synthesized chitosan-tripolyphosphate beads to Cu(II) ions, and used SEM/EDS, XPS, and TEM to examine the properties of zero-valent copper-chitosan nanocomposites. The results showed that, the adsorption behavior of hexavalent chromium from aqueous solution onto fabricated nanocomposites has better adsorption capacity than that of the chitosan-tripolyphosphate beads.

A 'green' chitosan-silver nanoparticle composite as a heterogeneous as well as micro-heterogeneous catalyst

In this paper, we report on the catalytic activity of a new metal nanoparticle-polymer composite consisting of Ag nanoparticles (NPs) and environmentally friendly ('green') chitosan. The polymer (chitosan) not only acted as the reducing agent for the metal ions, but also stabilized the product NPs by anchoring them. The majority of the particles produced in this way had sizes less than 5 nm. The catalytic activity of the composite was investigated photometrically by monitoring the reduction of 4-nitrophenol (4NP) in the presence of excess NaBH(4) in water, under both heterogeneous and micro-heterogeneous conditions. The reaction was first order with respect to the concentration of 4NP. We also observed that the apparent rate constant, k(app), for the reaction was linearly dependent on the amount of Ag NPs present in the composite. Moreover, the turn-over frequency (TOF) of the catalyst was found to be (1.5 ± 0.3) × 10(-3) s(-1), when the reaction was carried out under heterogeneous conditions. The Ag NPs in the composite retained their catalytic activities even after using them for ten cycles. Our observations also suggest that the catalytic efficiency under micro-heterogeneous conditions is much higher than under heterogeneous conditions. Thus the composite we have represents an ideal case of an environmentally friendly and stable catalyst, which works under heterogeneous as well as micro-heterogeneous conditions with the advantage of nanoscopic particles as the catalyst.

From Hydrocolloids to High Specific Surface Area Porous Supports for Catalysis

Polysaccharide hydrogels are effective supports for heterogeneous catalysts. Their use in solvents different from water has been hampered by their instability upon drying. While the freeze-drying process or air-drying of hydrocolloid gels led to compact solids with a low surface area, drying the gel in CO2 beyond the critical point provided mesoporous materials with a high specific surface area. Their effectiveness as a support for catalysis was exemplified in the reaction of substitution of an allyl carbonate with morpholine catalyzed by the hydrosoluble Pd(TPPTS)3 complex. The influence of water on the catalytic activity and the properties of the support was evidenced.

Review on green chemistry — Suzuki cross coupling in aqueous media

The Suzuki cross-coupling reaction is a very efficient, reliable, and environmentally friendly method for the introduction of novel carbon–carbon bonds into molecules. This review summarizes recent advances in the use of the reaction in aqueous media with a focus on different types of ligands and the ligandless protocols currently in use. Several synthetic targets for the reaction have been mentioned. The work summarizes recent results from studies on asymmetric Suzuki reactions performed in organic – aqueous mixed solvents.Key words: Suzuki reaction, green chemistry, metal-catalyzed cross-coupling reactions, aqueous synthesis media.

Chitosan-supported palladium catalyst. IV. Influence of temperature on nitrophenol degradation and thermodynamic parameters

Glutaraldehyde cross-linked chitosan was loaded with palladium and then reduced using an in situ hydrogen generation procedure (Zn in sulfuric acid solution) to prepare a chitosan-supported palladium catalyst. This catalyst was successfully used to degrade nitrophenol in dilute solutions in the presence of sodium formate as the hydrogen donor. The influence of the initial concentration of nitrophenol and sodium formate was studied in order to determine the minimum molar ratio between these compounds required to achieve complete conversion of the nitrogenous product at two temperatures. Increasing the temperature decreased the excess of hydrogen donor required for complete conversion of nitrophenol. The temperature was also varied between 10 and 60 degrees C in order to determine the activation energy. The pseudo first-order equation was shown to fit degradation kinetics in most cases; however, for some cases it was necessary to use a variable-order equation to model the kinetics.