ZnO nanoparticles (NPs) were synthesized using Rosmarinus officinalis leaf extract at 80 °C (ZnO-80) and 180 °C (ZnO-180). The powder was characterized and tested for the degradation of methylene blue (MB) and crystal violet (CV) under sunlight. FTIR analyzes revealed that Rosmarinus officinalis leaf extract contains phenolic compounds, and accordingly a mechanism for the formation of ZnO NPs was proposed. The characterizations by XRD, TEM and SEM and fluorescence spectroscopy showed that ZnO-80 NPs have smaller size than those of ZnO-180 which exhibited flakier agglomerated spherical structures. Photocatalytic tests showed that ZnO-80 degraded MB by 99.64% in 45 min while ZnO-180 degraded it by 98.82% in 60 min. The superior performance of ZnO-80 over ZnO-180 is due to the fact that ZnO-80 has smaller crystallites, higher specific surface area and higher pore volumes than ZnO-180. When reused, ZnO-80 only showed a slight decrease in the rate of degradation (2.95%). These results indicate that ZnO-80 can be considered as a promising photocatalyst for wastewater treatment. It was prepared by a simple and inexpensive procedure, and unlike many photocatalytic tests using an artificial light source, in the present work sunlight was used. GRAPHICAL ABSTRACT

The reactivity of Co_1.5PW₁₂O₄₀ in the direct synthesis of dimethyl carbonate (DMC) from CO₂ and CH₃OH was investigated. The synthesized catalyst has been characterized by means of FTIR, XRD, TG, and DTA and tested in gas phase under atmospheric pressure. The effects of the reaction temperature, time on stream, and methanol weight hourly space velocity (MWHSV) on the conversion and DMC selectivity were investigated. The highest conversion (7.6%) and highest DMC selectivity (86.5%) were obtained at the lowest temperature used (200 °C). Increasing the space velocity MWHSV increased the selectivity of DMC, but decreased the conversion. A gain of 18.4% of DMC selectivity was obtained when the MWHSV was increased from 0.65 h^-1 to 3.2 h^-1.

The cationic ring-opening polymerization reaction of tetrahydrofuran at 20 ºC was catalyzed by H₃PW₁₂O₄₀·13H₂O as solid acid catalyst. The effect of the proportions of acetic anhydride and catalyst, reaction time and support on the polymerization reaction was investigated. It has been found that the yield and the viscosity of the polymer depend on the proportion of acetic anhydride, the presence of the latter in the reactant mixture being required for the ring-opening. The catalytic activity of the alumina-supported heteropolyacid results showed that Brønsted acid sites are more effective than Lewis ones for the cationic ring-opening polymerization.

Fe-doped ZnO nanoparticles (NPs) with different Fe contents (0.1–5.0 wt%) were prepared using extract of wild olive leaves growing in Saudi Arabia (region of Abha). The biosynthesized NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL). Characterization results showed that undoped ZnO and Fe-doped ZnO powders were crystallized in the wurtzite structure with a small shift for the doped samples. Neither Fe ₃ O ₄ nor another iron oxide phase was observed in the samples, which proves the incorporation of Fe into the ZnO lattice. Doping has a pronounced effect on the physical and optical properties. Indeed, the size of the crystallites, the energy of the bandgap as well as the intensity of the PL emission decreased with the Fe content. Photocatalytic tests revealed that the doped samples degraded methyl orange (MO) more efficiently than pure ZnO and pure Fe ₃ O ₄ . Moreover, the photocatalytic activity improved with increasing Fe content. The best photocatalyst of the series (Fe–ZnO-5) was found degrading MO by 92.1%, in 90 min in a pseudo-first order reaction.

A series of Keggin-type heteropoly compounds (HPC) having different countercations (Co, Fe) and different addenda atoms (W, Mo) were synthesized and characterized by means of Fourier-Transform Infrared Spectrometer (FT-IR) and X-ray powder diffraction (XRD). The catalytic properties of the prepared catalysts for the dimethyl carbonate (DMC) synthesis from CO₂ and CH₃OH were investigated. The experimental results showed that the catalytic activity is significantly influenced by the type of the countercation and addenda atoms transition metal. Among the catalysts examined, Co_1.5PW₁₂O₄₀ is the most active for the DMC synthesis, owing to the synergetic effect between Co and W. Investigating the effect of the support showed that the least acidic one (Al₂O₃) enhanced the conversion but decreased the DMC selectivity in favor of that of methyl formate (MF), while that of dimethoxy methane remained stable.