Single-pot tandem oxidative/C-H modification amidation process using ultrasmall PdNP-encapsulated porous organosilica nanotubes

Herein, we studied a single-pot method with a dual catalysis process towards the conversion of primary aromatic alcohols to amides using ultrasmall PdNPs of controlled uniform size (1.8 nm) inside hybrid mesoporous organosilica nanotubes (MO-NTs). The catalyst exhibited excellent performance in water under mild conditions and showed high stability. The catalytic activity towards the tandem oxidation of alcohols in the presence of amine salts and H2O2 to their corresponding amides without producing byproducts was evaluated, and high yields were obtained for all products. The structure of the organosilica nanotubes containing palladium nanoparticles was investigated using various characterization techniques such as XRD, TEM, BET, solid-state 29Si NMR and solid-state 13C CP MAS NMR. Catalyst recycling tests showed that the catalytic power of PdNPs@B-SNTs was preserved after 8 cycles and a slight decrease in catalyst activity was observed.

A nickel nanoparticle engineered CoFe2O4/SiO2-NH2@carboxamide composite as a novel scaffold for the oxidation of sulfides and oxidative coupling of thiols

The purpose of this work was to prepare a new Ni-carboxamide complex supported on CoFe2O4 nanoparticles (CoFe2O4/SiO2-NH2@carboxamide-Ni). The carboxamide host material unit generated cavities that stabilized the nickel nanoparticles effectively and prevented the aggregation and separation of these particles on the surface. This compound was appropriately characterized using FT-IR spectroscopy, FE-SEM, ICP-OES, EDX, XRD, TGA analysis, VSM, and X-ray atomic mapping. The catalytic oxidation of sulfides and oxidative coupling of thiols in the presence of the designed catalyst was explored as a highly selective catalyst using hydrogen peroxide (H2O2) as a green oxidant. The easy separation, simple workup, excellent stability of the nanocatalyst, short reaction times, non-explosive materials as well as appropriate yields of the products are some outstanding advantages of this protocol.

Study on heteropolyacid-based catalysts with high activity and reusability for isoprene synthesis from formaldehyde and isobutene

SiW/S-1 catalysts exhibited excellent catalytic activity and reusability due to the highly dispersed SiW and MFI structure of S-1.

Utilization of iron tailings to prepare high-surface area mesoporous silica materials

Iron tailings are fine, stable and complex materials, which are mainly composed of minerals and metal oxides. Residual silicon in iron tailings can be used to prepare mesoporous silica materials applied to energy storage, environmental protection and other fields. This paper reported a novel synthesis strategy from iron tailings to high-surface area hexagonally ordered mesoporous silica materials in an innovative non-hydrothermal system at room temperature. A pretreatment process involving acid leaching and hydrothermal alkaline reaction was vital to the successful utilization of iron tailings. X-ray fluorescence (XRF) data suggested that about 95% of the silicon of iron tailings changed to the silicate as a silicon source. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-adsorption-desorption isotherms, Fourier transform infrared (FTIR) spectroscopy, Thermogravimetry and differential scanning calorimetry (TG-DSC) and ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy. The SAXRD patterns of mesoporous silica materials exhibited an intense (100) diffraction peak and two weak (110, 200) diffraction peaks, corresponding to characteristic of the ordered mesoporous lattice. TEM images further confirmed the hexagonally ordered porous structure of mesoporous silica materials. The WAXRD patterns and ²⁹Si MAS NMR spectra of the samples indicated that mesoporous silica materials were composed of amorphous SiO₂. The obtained mesoporous silica materials had a high surface area of 1915 m²/g and pore volume of 1.32 cm³/g. Furthermore, the evolution from iron tailings to mesoporous silica materials was elucidated and a proposed synthesis mechanism was discussed. Collectively, these results provided an insight into efficient recycling of iron tailings and the production of advanced functional materials from solid waste.

In vitro antiproliferative effect of vanadium complexes bearing 8-hydroxyquinoline-based ligands – the substituent effect

This is the first comprehensive study demonstrating the antiproliferative effect of vanadium complexes bearing 8-hydroxyquinoline (quinH) ligands, including the parent and –CH₃ (Me), –NO₂, –Cl and –I substituted ligands, on HCT116 and A2780 cancer cell lines.

Functionalized Silicas for Metal-Free and Metal-Based Catalytic Applications: A Review in Perspective of Green Chemistry

Heterogeneous catalysis plays a key role in promoting green chemistry through many routes. The functionalizable reactive silanols highlight silica as a beguiling support for the preparation of heterogeneous catalysts. Metal active sites anchored on functionalized silica (FS) usually demonstrate the better dispersion and stability due to their firm chemical interaction with FSs. Having certain functional groups in structure, FSs can act as the useful catalysts for few organic reactions even without the need of metal active sites which are termed as the covetous reusable organocatalysts. Magnetic FSs have laid the platform where the effortless recovery of catalysts is realized just using an external magnet, resulting in the simplified reaction procedure. Using FSs of multiple functional groups, we can envisage the shortened reaction pathway and, reduced chemical uses and chemical wastes. Unstable bio-molecules like enzymes have been stabilized when they get chemically anchored on FSs. The resultant solid bio-catalysts exhibited very good reusability in many catalytic reactions. Getting provoked from the green chemistry aspects and benefits of FS-based catalysts, we confer the recent literature and progress focusing on the significance of FSs in heterogeneous catalysis. This review covers the preparative methods, types and catalytic applications of FSs. A special emphasis is given to the metal-free FS catalysts, multiple FS-based catalysts and magnetic FSs. Through this review, we presume that the contribution of FSs to green chemistry can be well understood. The future perspective of FSs and the improvements still required for implementing FS-based catalysts in practical applications have been narrated at the end of this review.

Palladium Comprising Dicationic Bipyridinium Supported Periodic Mesoporous Organosilica (PMO): Pd@Bipy–PMO as an Efficient Hybrid Catalyst for Suzuki–Miyaura Cross-Coupling Reaction in Water

In this study, we developed a novel catalysts consisting of periodic mesoporous organosilica functionalized with bipyridinium ionic liquid supported palladium. The physiochemical properties of the hybrid catalyst were investigated using Fourier transform infrared spectroscopy, small angle X–ray powder diffraction, field emission scanning electron microscope, transmission electron microscope, nitrogen adsorption–desorption analyses, and atomic absorption spectroscopy. The stabilized Pd species inside the mesochannels provided good catalytic efficiency for the Suzuki–Miyaura coupling reactions in water. The activity of the designed catalysts retained for several consecutive recycle runs. The stability, recoverability, and reusability of the designed heterogeneous catalyst were also studied under various reaction conditions.