ZnCl2 loaded TiO2 nanomaterial: an efficient green catalyst to one-pot solvent-free synthesis of propargylamines

Ultrasonic irradiation-assisted MnFe2O4 nanoparticles catalyzed solvent-free selective oxidation of benzyl alcohol to benzaldehyde at room temperature

Magnetic nanoparticles (NPs) play a vital role in heterogeneous catalysis because of their easy separation, and effective recyclability. Herein, we report the synthesis of MnFe2O4 NPs for use as catalysts in the selective oxidation of benzyl alcohol to benzaldehyde under mild conditions. The MnFe2O4 NPs have been synthesized by precipitation method followed by hydrothermal ageing at 180 °C for 4.0 h. We have investigated the effect of chitosan and carboxymethyl cellulose on the size or morphology of the formed MnFe2O4 NPs. The X-ray diffraction study confirms the formation of pure and crystalline MnFe2O4 with varying average crystallite sizes ranging from 18 to 28 nm based on the type of additive used. The electron microscopy study reveals that the additive plays a significant role in controlling the morphology of the formed MnFe2O4 NPs. These MnFe2O4 NPs exhibit superparamagnetic behaviour at room temperature and can effectively catalyze the solvent-free selective oxidation of benzyl alcohol to benzaldehyde in the presence of tert-butyl hydroperoxide at room temperature under ultrasonic irradiation. The developed protocol can be extended to various substituted benzyl alcohols having both the electron withdrawing and electron donating groups to afford moderate to excellent yield of the products. The catalyst is magnetically retrievable, highly stable, and can be reused up to the sixth run without significant loss of catalytic activity.

Electroless Ni plated nanostructured TiO2 as a photocatalyst for solar hydrogen production

Herein, we have demonstrated a facile electroless Ni coated nanostructured TiO₂ photocatalyst for the first time. More significantly the photocatalytic water splitting shows excellent performance for hydrogen production which is hitherto unattempted. The structural study exhibits majorly the anatase phase along with the minor rutile phase of TiO₂. Interestingly, electroless nickel deposited on the TiO₂ nanoparticles of size 20 nm shows a cubic structure with nanometer scale Ni coating (1-2 nm). XPS supports the existence of Ni without any oxygen impurity. The FTIR and Raman studies support the formation of TiO₂ phases without any other impurities. The optical study shows a red shift in the band gap due to optimum nickel loading. The emission spectra show variation in the intensity of the peaks with Ni concentration. The vacancy defects are pronounced in lower concentrations of Ni loading which shows the formation of a huge number of charge carriers. The electroless Ni loaded TiO₂ has been used as a photocatalyst for water splitting under solar light. The primary results manifest that the hydrogen evolution of electroless Ni plated TiO₂ is 3.5 times higher (1600 μmol g^-1 h^-1) than pristine TiO₂ (470 μmol g^-1 h^-1). As shown in the TEM images, nickel is completely electroless plated on the TiO₂ surface, which accelerates the fast transport of electrons to the surface. It suppresses the electron-hole recombination drastically which is responsible for higher hydrogen evolution using electroless Ni plated TiO₂. The recycling study exhibits a similar amount of hydrogen evolution at similar conditions which shows the stability of the Ni loaded sample. Interestingly, Ni powder loaded TiO₂ did not show any hydrogen evolution. Hence, the approach of electroless plating of nickel over the semiconductor surface will have potential as a good photocatalyst for hydrogen evolution.

Treatment on thiodicarb in pesticide wastewater with walnut shells-derived carbon and its improved modification: adsorption behavior

The health problems caused by water pollution cannot be ignored, and the contribution of pesticides to water pollution has also become increasingly unignorable. The modified semi-coke as an adsorbent for reducing pesticide pollution to water was obtained from activated semi-coke which was modified by nitric acid (HNO₃). The semi-coke was obtained by carbonization using 60 mesh walnut shell powder. After acid-base deashing, the semi-coke is dipped into zinc chloride (ZnCl₂) solution to obtain activated semi-coke. Through BET analysis, the specific surface areas of semi-coke, activated semi-coke and modified semi-coke were 26.8 m²/g, 243.9 m²/g, and 339.6 m²/g respectively. An extremely high adsorption capacity of the adsorbents which is used to treat wastewater was achieved. The optimum adsorption conditions for modified semi-coke on thiodicarb solution were 30 mg/L of thiodicarb solution, adsorbent dosage of 0.01 g, adsorption temperature of 25 °C and adsorption time of 90 min. The optimum adsorption amount of 29.54 mg/gsor was achieved (sor is the abbreviation for sorbent). Moreover, through kinetics study, the result manifests that the modified semi-coke adsorption process is more fitted to the second-order kinetic model. This study provided a research implication theoretically for the treatment of pesticides in water.

Solvent-free synthesis of propargylamines: an overview

Propargylamines are a class of compounds with many pharmaceutical and biological properties. A green approach to synthesize such compounds is very relevant. This review aims to describe the solvent-free synthetic approaches towards propargylamines via A3 and KA2 coupling reactions covering the literature up to 2021.

A core–shell superparamagnetic metal–organic framework: a recyclable and green catalyst for the synthesis of propargylamines

This is the first report on the use of a magnetic metal–organic framework for the green synthesis of propargylamine derivatives.