Palladium Nanoparticles Supported on Hydroxyapatite Nanospheres: Highly Active, Reusable and Green Catalyst for Suzuki - Miyaura Cross Coupling Reactions under Aerobic Conditions

Permanently polarized hydroxyapatite, an outstanding catalytic material for carbon and nitrogen fixation

Hydroxyapatite (HAp) is a well-known ceramic material widely used in the biomedical field. This review summarizes the very recent developments on permanently polarized HAp (pp-HAp), a HAp variety with tuned electrical properties that confer remarkable catalytic activity. pp-HAp is obtained by applying a thermal stimulation polarization process (TSP), which consists on a DC electric voltage of 500 V at 1000 °C, to previously sintered HAp. The TSP not only increases the crystallinity, reducing the defects in the crystal lattice, but also creates charges that accumulate at the crystalline boundaries and at the surface of microscopic grains, boosting the electrical conductivity. Finally, the successful utilization of pp-HAp in the catalytic fixation of carbon and nitrogen from CO₂ and N₂ gases, respectively, is reported and the formation of different products of chemical interest (e.g. amino acids, ethanol and ammonium) as a function of the reaction conditions (i.e. feeding gases and presence/absence of UV illumination) and catalyst plasticity is discussed. pp-HAp exhibits important advantages with respect to other consolidated catalysts, which drastically increases the final energetic net balance of the reactions.

Palladium nanoparticles decorated on amine functionalized graphene nanosheets as excellent nanocatalyst for the hydrogenation of nitrophenols to aminophenol counterparts

We reported the improved catalytic property of Pd (0) nanoparticles decorated on amine-functionalized graphene nanosheets (Pd/GNS-NH₂) for the hydrogenation of nitrophenol derivatives in the presence of NaBH₄ at moderate conditions. Pd/GNS-NH₂ nanocatalyst was synthesized by the deposition-reduction method. Sundry techniques such as ICP-OES, P-XRD, XPS, TEM, HR-TEM and EDX have been applied to explain the structure and morphology of the Pd/GNS-NH₂ nanocatalyst. The results show that the Pd (0) nanoparticles are perfectly dispersed on the surface of the GNS-NH₂ support material (d_mean = 1.38-2.63 nm). The catalytic activity of the Pd/GNS-NH₂ nanocatalyst was tested in the hydrogenation of nitrophenol derivatives in water in the presence of NaBH₄ as reductant and the excellent activity of nanocatalyst have been detected against 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol derivatives with 116.8, 65.9, 42.8 and 11.4 min^-1 initial TOF values, respectively. Another important point is that the nanocatalyst has very high reusability performance (at 5th reuse between 71.5 and 91.5%) for the hydrogenation of nitrophenols. Finally, catalytic studies have been carried out at various temperatures to calculate the E_a, ΔH^≠ and ΔS^≠.

Liquid-phase catalysis by single-size palladium nanoclusters supported on strontium titanate: size-specific catalysts for Suzuki–Miyaura coupling

Size-specific catalysis by single-size palladium nanoclusters.