Yolk Shell Nanocatalysts Research Articles

Facile and green fabrication of copper‐based magnetically recoverable yolk–shell nanocatalysts with high catalytic performance for nitroaromatic reduction

A simple method was reported to achieve a green yolk–shell Fe3O4@SiO2@CuO nanocatalysts (YS‐Fe3O4@SiO2@CuO). Glucose (G) and lactose (L), as a grafting agent, were applied for decorating CuO on the magnetic nanoparticles surface and then using calcination method, yolk–shell structure was obtained. Characterization of nanocatalysts was carried out using inductively coupled plasma–optical emission spectrometry (ICP‐OES), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX)‐Mapping, thermogravimetric analysis (TGA), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), Brunauer, Emmett, and Teller (BET), and vibrating sample magnetometer (VSM) analyses and the results confirmed the successful synthesis of these catalysis. The activity of the nanocatalysts were studied to reduce nitroaromatic compounds monitoring by UV–Vis spectra. In the model reaction, 4‐nitrophenol was reduced using YS‐Fe3O4@SiO2@CuO(G) and YS‐Fe3O4@SiO2@CuO(L), with the activity factors (k′) of 3218 and 2023 s−1 g−1, and rate constants (Kapp) of 0.56 and 1.19 min−1, respectively. The advantages of prepared nanocatalysts were good stability and high conversion. The magnetic property of nanocatalysts makes them easy to recover in multiple cycles.

A Mini Review on Yolk-Shell Structured Nanocatalysts.

Yolk-shell structured nanomaterials, possessing a hollow shell and interior core, are emerging as unique nanomaterials with applications ranging from material science, biology, and chemistry. In particular, the scaffold yolk-shell structure shows great promise as a nanocatalyst. Specifically, the hollow shell offers a confined space, which keeps the active yolk from aggregation and deactivation. The inner void ensures the pathway for mass transfer. Over the last few decades, many strategies have been developed to endow yolk-shell based nanomaterials with superior catalytic performance. This minireview describes synthetic methods for the preparation of various yolk-shell nanomaterials. It discusses strategies to improve the performance of yolk-shell catalysts with examples for engineering the shell, yolk, void, and related synergistic effects. Finally, it considers the challenges and prospects for yolk-shell nanocatalysts.

Mesoporous Silica Encapsulated Metal-Organic Frameworks for Heterogeneous Catalysis

Encapsulation of metal-organic frameworks (MOFs) with a shell of mesoporous silica can boost overall performance of MOFs, offering versatility for synthetic architecture of integrated nanocatalysts with reactor-like features. Recently, Yu et al. report a green approach to make yolk-shell nanoreactors.

Palladium functionalized yolk-shell nanorattles with tunable surface wettability for controllable catalytic selectivity

Herein, we demonstrated a versatile method to synthesize tunable surface wettability nano-rattles with a removable palladium nanocluster and a hydrophilic/hydrophobic polymeric shell as a nanocatalyst for the hydrogenation of nitroaromatic compounds as model reactions. The yolk-shell nanocatalysts were prepared via combination of distillation precipitation polymerization of divinylbenzene and 4-chloromethylstyrene (CMSt) in presence of 3-(trimethoysilyl)rpopyl methacrylate (MPS)-modified Pd@SiO2 microspheres as seeds, surface-initiated atomic transferring radical polymerization (SI-ATRP) of acrylamide (Am) with Cu(I)Cl as a catalyst and Me6TREN as a ligand, and the subsequently selective removal of the sandwiched silica core. As a result, the rattle-type nano-colloids exhibited a remarkable catalytic selective performance for the hydrogenation of different hydrophobic and hydrophilic reactants due to presence of a cavity for storing and hydrophilic/hydrophobic polymeric shell for fast transporting reagents and products as well as the protective effect to prevent the coagulation of palladium in nano-rattles.

Yolk–shell or yolk-in-shell nanocatalysts? A proof-of-concept study

A new class of yolk-in-shell nanocatalysts has been developed, which shows incredibly improved catalytic activity and recyclability compared to yolk–shell nanocatalysts.

Catalytic Nanoreactors of Au@Fe3O4 Yolk–Shell Nanostructures with Various Au Sizes for Efficient Nitroarene Reduction

Au@Fe3O4 yolk–shell nanocatalysts based on the thermal decomposition of iron pentacarbonyl in the presence of 2.5–10-nm Au core nanoparticles were successfully fabricated for the catalytic reduction of nitroarenes. The particle sizes of the Au@Fe3O4 nanostructures were in the range 8–15 nm, with Fe3O4 shell layer thicknesses of 2.0–2.4 nm. The Fe3O4 layer not only can form a magnetic shell for recovery but also enables the protection of the catalytic activity of the Au core nanoparticles toward the reduction of nitrobenzene derivatives including 2-nitrophenol, 4-nitrophenol, 4-nitrotoluene, and 1-chloro-4-nitrobenzene in the presence of NaBH4. The catalytic performance of Au@Fe3O4 is highly dependent on the particle size of the Au core materials and the substituent groups of the nitroarenes. The reduction rates of nitroarenes with electron-withdrawing groups were found to be 2.3–2.6 times higher than those of nitroarenes with electron-donating groups. In addition, the reduction of nitroarenes by the Au@Fe...

Surfactant-free Pd@pSiO2 yolk–shell nanocatalysts for selective oxidation of primary alcohols to aldehydes

The surfactant-free Pd@pSiO2 yolk–shell nanoparticles proved to be an efficient catalyst for the oxidation of substituted benzyl alcohols.

Fabrication of Magnetic Yolk–Shell Nanocatalysts with Spatially Resolved Functionalities and High Activity for Nitrobenzene Hydrogenation

In cracking from: Highly engineered bifunctional yolk-shell nanocatalysts with tailored structural configuration, that is, hollow carbon spheres as the matrix, entrapped magnetite nanoparticles in the core, and in situ formed and highly dispersed noble metal nanoparticles within the carbon shells as active catalytic sites, were prepared. These nanocatalysts show high activity, reusability, and good magnetic separation properties.

Porosity Control of Pd@SiO2 Yolk–Shell Nanocatalysts by the Formation of Nickel Phyllosilicate and Its Influence on Suzuki Coupling Reactions

The surface of Pd@SiO(2) core-shell nanoparticles (1) was simply modified by the formation of nickel phyllosilicate. The addition of nickel salts formed branched nickel phyllosilicates and generated pores in the silica shells, yielding Pd@SiO(2)-Niphy nanoparticles (Niphy = nickel phyllosilicate; 2, 3). By removal of the silica residue, Pd@Niphy yolk-shell nanoparticles (4) was uniformly obtained. The four distinct nanostructures (1-4) were employed as catalysts for Suzuki coupling reactions with aryl bromide and phenylboronic acid, and the conversion yields were in the order of 1 < 2 < 3 < 4 as the pore volume and surface area of the catalysts increased. The reaction rates were strongly correlated with shell porosity and surface exposure of the metal cores. The chemical inertness of nickel phyllosilicate under the basic conditions rendered the catalysts reusable for more than five times without loss of activity.

Extremely Active Pd@pSiO2 Yolk–Shell Nanocatalysts for Suzuki Coupling Reactions of Aryl Halides

In the present study, we optimize the yolk–shell nanostructure in a palladium–silica system for the purpose of attaining high activity in Suzuki cross-coupling reactions. Pd@porous SiO2 (Pd@pSiO2) yolk–shell nanoparticles, bearing tiny palladium cores and highly porous silica hollow shells, were synthesized by direct silica coating and partial etching of the silica layers. High temperature treatment removed all surfactants around the catalyst surface and generated large pores on the silica shells. The resulting Pd@pSiO2 yolk–shell catalysts exhibited extremely high initial turnover frequency of 78000 h–1, as well as excellent reusability of more than 10 times in a standard Suzuki coupling reaction. The catalysts also catalyzed Suzuki reactions with various substrates including bromo- and chlorobenzene very well.