Ordered interface mesoporous immobilized Pd pre-catalyst: En/Pd complexes embedded inside the SBA-15 as an active, reusable and selective phosphine-free hybrid catalyst for the water medium Heck coupling process

Controlled synthesis of Ru-single-atoms on ordered mesoporous phosphine polymers for microwave-assisted conversion of biomass-derived sugars to artificial sweeteners

Atomically dispersed metal-single-atoms have become a frontier in solid catalysis due to their characteristic electronic properties. However, for biomass conversion, employing metal-single-atoms as catalysts is rather challenging since they suffer from poor selectivity and yield due to inadequate metal-support interactions. We show here that Ru/triphenylphosphine (PPh)-based ordered mesoporous polymers afford high yields of reduced sugars, xylitol (yield ∼95%) and sorbitol (yield ∼65%) in a microwave reactor with formic acid as the only hydrogen donor. We have established a unique relationship within Ru/triphenylphosphine that shows an important ligand effect, in contrast to, Ru/triphenylamine and Ru/catechol. The tailored electronic properties in Ru/phosphine were thoroughly examined by using state-of-the-art experimental techniques viz. EXAFS, XANES, XPS, DRIFTS and HAADF-STEM. The resulting phosphine-modified catalysts show a promotion in activity and selectivity towards less vulnerable aldehydes for hydrogenation, further confirmed by DFT calculations. This finding reveals a new protocol to tailor the activity of metal-single-atoms utilizing functional porous polymers as nanoreactors.

Zn (II)-porphyrin-based photochemically green synthesis of novel ZnTPP/Cu nanocomposites with antibacterial activities and cytotoxic features against breast cancer cells

This study focuses on synthesizing novel nanocomposites, zinc(II)tetrakis(4-phenyl)porphyrin/Cu nanoparticles (ZnTPP/Cu-NPs),with antibacterial activity, fabricated through a single-step green procedure. In this regard, the self-assembly of ZnTPP was carried out through an acid-base neutralization method to prepare ZnTPP nanoparticles. Then, the copper nanoparticles (Cu-NPs) were grown on ZnTPP nanoparticles through a visible-light irradiated photochemical procedure in the absence and presence of polyacrylic acid (PAA) as a modulator. The effect of PAA on the morphological properties of the prepared nanocomposites was evaluated. Eventually, the antibacterial activity of nanocomposites with different morphologies was investigated. In this way, the average zone of inhibition growth of diameter, minimum inhibitory concentration, and minimum bactericidal concentration values was determined. Besides, the cytotoxicity of the nanocomposites was evaluated by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay MCF-7and (HEK-293) cell lines. The specific features of the synthesized nanocomposites identified them as antibacterial compounds which have therapeutic effects on breast cancer.

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.

Facile d-band tailoring in Sub-10 nm Pd cubes by in-situ grafting on nitrogen-doped graphene for highly efficient organic transformations

We demonstrate for the first time the in-situ synthesis of Pd nanocubes (PdNC) on nitrogen-doped reduced graphene oxide (NRGO) for facile organic transformations wherein the cubic morphology of Pd can only be realized by precision-controlled acid additions in the tune of 0.02 pH variations in the reaction medium. Due to the intimate contact arising from atom-by-atom addition of Pd on NRGO, the composite has exhibited a pronounced catalyst to support charge transfer effect, shift in the d-band center, and lowering of charge-transfer resistance when compared with PdNC-NRGO ex-situ composites prepared by mixing of the preformed components of PdNC and NRGO or PdNCs alone. The activities of these catalysts were tested for the Suzuki coupling and nitroarene reduction reactions using water as an industry-friendly solvent. In both, the in-situ deposited sample exhibited substantially higher catalytic activity as well as stability when compared with an ex-situ sample or pure PdNCs. We show that a very high turnover frequency of ~31300 h^-1 and ~900 h^-1 are achievable by using the in-situ deposited PdNC-NRGO composite for Suzuki coupling reactions and nitroarene reduction respectively, better than the state-of-the-art catalysts developed recently, in addition to high recyclability.

Recent advances in the application of silica nanostructures for highly improved water treatment: a review

The demand for high-quality safe and clean water supply has revolutionized water treatment technologies and become a most focused subject of environmental science. Water contamination generally marks the presence of numerous toxic and harmful substances. These contaminants such as heavy metals, organic and inorganic pollutants, oil wastes, and chemical dyes are discharged from various industrial effluents and domestic wastes. Among several water treatment technologies, the utilization of silica nanostructures has received considerable attention due to their stability, sustainability, and cost-effective properties. As such, this review outlines the latest innovative approaches for synthesis and application of silica nanostructures in water treatment, apart from exploring the gaps that limit their large-scale industrial application. In addition, future challenges for improved water remediation and water quality technologies are keenly discussed.

Applications of SBA-15 supported Pd metal catalysts as nanoreactors in C-C coupling reactions

Nanoreactors are material structures with engineered internal cavities which create exclusive confined nanoscale surroundings for chemical reactions. The cavities of mesoporous silica SBA-15 can be used as nanoreactors for incorporating catalytic species such as metal nanoparticles, complexes etc. Since SBA-15 silica has a neutral framework, organic functional groups and heteroatoms have been embedded by direct or post-synthesis approaches in order to modify their functionality. Palladium is the most used transition metal for C-C bond formations. Because of the great importance of C-C coupling reactions, this review article aims at providing a deep insight into the state of art in the field of the synthesis and the application of mesoporous SBA-15 silica-supported Pd catalysts in C-C coupling transformations. In most cases, synthesis and modification of the catalyst, time and yield of reactions, recyclability and leaching of the Pd species from the SBA-15 support are discussed to reveal the role of SBA-15 in C-C coupling reactions.

The influence of carbon surface chemistry on supported palladium nanoparticles in heterogeneous reactions

The surface chemistry of nanocarbon support can tailor chemical properties of precious metal nanoparticle/nanocarbon hybrid catalyst in heterogeneous reactions. We report on modified reduced graphene oxide (rGO) support with ionic liquid-derived carbonaceous surface for palladium nanoparticle (Pd NPs) decoration and their actions in different heterogeneous reactions. The surface chemistry of support materials was characterized in detail, and the influence of which on the formation and distribution of metal particles was further investigated. Three different types of reactions including Suzuki-Miyaura coupling reaction, CO oxidation and phenol reduction were examined in terms of reactivity and selectivity. The roles of substituted nitrogen in graphitic lattice and grafted groups on the carbon surface were exploited. Nitrogen-doping can give rise to changes in electronic properties of supported metals, and the Lewis basicity of the doped nitrogen atoms can favor the adsorption of acidic reactants in phenol reduction. The grafted groups derived a negative impact to the Suzuki-Miyaura coupling reaction, due to the involvement of larger reactant molecules, despite that they could prevent significant sintering of Pd NPs in the CO oxidation.

Efficient tandem aqueous room temperature oxidative amidations catalysed by supported Pd nanoparticles on graphene oxide

Pd nanoparticles deposited onto graphene oxide nanosheets (SE-GO/Pd_NPs) were found to successfully promote two oxidative processes for the synthesis of amides, providing alternative possibilities to these important compounds.

Generation of uniform and small particle size of palladium onto the SH-decorated SBA-15 pore-walls: SBA-15/(SH)XPd–NPY as a recoverable nanocatalyst for Suzuki–Miyaura coupling reaction in air and water

Uniform and small particle size of palladium was generated onto the SH-decorated SBA-15 pore-walls.