A Magnetically Recyclable Nanocomposite Catalyst for Olefin Epoxidation

Functionalized Ordered Mesoporous Silicas (MCM-41): Synthesis and Applications in Catalysis

Mesoporous silica sieves are among the most studied nano-objects due to their stable pore structure and easy preparation. In particular, MCM-41 have attracted increasing research attention due to their chemical versatility. This review focuses on the synthesis and regioselective functionalization of MCM-41 to prepare catalytic systems. The topics covered are: mono and di-functionalized MCM-41 as basic and acid catalysts, catalysts based on metallic complexes and heteropolyacids supported onto MCM-41, metallic nanoparticles embed onto functionalized MCM-41 and magnetic MCM-41 for catalytic purposes.

Synthesis of magnetic core–shell Fe3O4@TiO2 nanoparticles from electric arc furnace dust for photocatalytic degradation of steel mill wastewater

Fabrication of Fe₃O₄ from EAF dust using a hydrothermal method and Fe₃O₄@TiO₂ using a sol–gel method for the photocatalytic degradation of steel industry wastewater.

Development of the catalytic reactivity of an oxo–peroxo Mo(vi) Schiff base complex supported on supermagnetic nanoparticles as a reusable green nanocatalyst for selective epoxidation of olefins

A novel ancillary branch coated oxo–peroxo Mo(vi)tetradentate Schiff base complex on superparamagnetic nanoparticles as an epoxidation catalyst.

A Highly Stable and Magnetically Recyclable Nanocatalyst System: Mesoporous Silica Spheres Embedded with FeCo/Graphitic Shell Magnetic Nanoparticles and Pt Nanocatalysts

We have developed a highly stable and magnetically recyclable nanocatalyst system for alkene hydrogenation. The materials are composed of mesoporous silica spheres (MSS) embedded with FeCo/graphitic shell (FeCo/GC) magnetic nanoparticles and Pt nanocatalysts (Pt-FeCo/GC@MSS). The Pt-FeCo/GC@MSS have superparamagnetism at room temperature and show type IV isotherm typical for mesoporous silica, thereby ensuring a large enough inner space (surface area of 235.3 m(2)  g(-1), pore volume of 0.165 cm(3)  g(-1), and pore diameter of 2.8 nm) to undergo catalytic reactions. We have shown that the Pt-FeCo/GC@MSS system readily converts cyclohexene into cyclohexane, which is the only product isolated and Pt-FeCo/GC@MSS can be seperated very quickly by an external magnetic field after the catalytic reaction is finished. We have demonstrated that the recycled Pt-FeCo/GC@MSS can be reused further for the same hydrogenation reaction at least four times without loss in the initial catalytic activity.

Selective isomerization of epoxides using magnetically recyclable ZSM-5 zeolite catalyst

The magnetically recyclable ZSM-5 zeolite (MZZ) with high catalytic activity, high efficiency in separation, recycling and long lifetime for epoxide isomerization reaction was presented.

An efficient synthesis of perhydro[1,2,4]triazolo[1,2-a][1,2,4]triazole-1,5-dithiones catalyzed by TiO2-functionalized nano-Fe3O4 encapsulated-silica particles as a reusable magnetic nanocatalyst

A nano-TiO₂ catalyst on was immobilized on a magnetic SiO₂ support to form a robust and magnetically recoverable Fe₃O₄@SiO₂–TiO₂ catalyst for the synthesis of perhydrotriazolotriazole derivatives by the condensation of aldazines at room temperature.

Size-controlled synthesis of water-dispersible superparamagnetic Fe3O4 nanoclusters and their magnetic responsiveness

Highly water-dispersible and size-controllable superparamagnetic Fe₃O₄ nanoclusters were synthesized by using sodium citrate with a mixed-solvent system, these nanoclusters can be used for color display and hyperthermia in biomedical applications.

Nanoscaled copper metal-organic framework (MOF) based on carboxylate ligands as an efficient heterogeneous catalyst for aerobic epoxidation of olefins and oxidation of benzylic and allylic alcohols

Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu3(BTC)2] (BTC = 1,3,5-benzenetricarboxylate) as a high-performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal-organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as-synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity.

Synthesis of a thin-layer MnO₂ nanosheet-coated Fe₃O₄ nanocomposite as a magnetically separable photocatalyst

A facile hydrothermal method combined with a mild ultrasonic means has been developed for the fabrication of a magnetically recyclable thin-layer MnO2 nanosheet-coated Fe3O4 nanocomposite. The photocatalytic studies suggest that the MnO2/Fe3O4 nanocomposite shows excellent photocatalytic efficiency and stability simultaneously for the degradation of methylene blue under UV-vis light irradiation. Moreover, its good acid resistance and stable recyclability are very important for its future practical application as a photocatalyst. Magnetic measurements verify that the MnO2/Fe3O4 nanocomposite possesses a ferromagnetic nature, which can be effectively separated for reuse by simply applying an external magnetic field after the photocatalytic reaction. This novel composite material may have potential applications in water treatment, degradation of dye pollutants, and environmental cleaning.

Palladium nanoparticles supported on agarose-functionalized magnetic nanoparticles of Fe3O4 as a recyclable catalyst for C–C bond formation via Suzuki–Miyaura, Heck–Mizoroki and Sonogashira–Hagihara coupling reactions

Palladium nanoparticles supported on agarose functionalized Fe₃O₄ catalyzed C–C bond formation reactions.

Assembling nanostructures for effective catalysis: supported palladium nanoparticle multicores coated by a hollow and nanoporous zirconia shell

We report the synthesis and catalytic activities of highly stable, hollow nanoreactors, called SiO(2)/Pd/h-ZrO(2), which consist of silica microsphere (SiO(2))-supported Pd nanoparticle multicores (Pd) that are encapsulated with a hollow and nanoporous ZrO(2) shell (h-ZrO(2)). The SiO(2)/Pd/h-ZrO(2) nanoreactors are fabricated by first synthesizing SiO(2)/Pd/SiO(2)/ZrO(2) microspheres, and then etching the inner SiO(2) shell with dilute NaOH solution. The hollow and nanoporous ZrO(2) shell of the nanoreactors serves two important functions: 1) it provides reactants direct access to the Pd nanoparticle multicores inside the SiO(2)/Pd/h-ZrO(2) nanoreactors during catalysis, and 2) it stabilizes the Pd nanoparticles or protects them from aggregation/sintering. The fabrication of such structures capable of protecting the Pd nanoparticles from aggregation/sintering is of particular interest considering the fact that Pd nanoparticles generally have a high tendency to aggregate because of their high surface energies. Furthermore, the structures are interesting because the Pd nanoparticles are designed and synthesized here to have 'naked' surfaces or no organic surface-passivating ligands-that are often necessary to stabilize metallic nanoparticles-in order to increase their catalytic efficiency. The resulting SiO(2)/Pd/h-ZrO(2) nanoreactors show excellent catalytic activity, as shown in the hydrogenation of olefins and nitro groups, even at room temperature under moderate hydrogen pressure. This stems from the SiO(2)/Pd/h-ZrO(2) microspheres' high surface area and their small, stable, and bare Pd nanoparticles. Furthermore, the SiO(2)/Pd/h-ZrO(2) nanoreactor catalysts remain fairly stable after reaction and can be recycled multiple times without losing their high catalytic activities.

Recycling functional colloids and nanoparticles

The stability and separation of colloids and nanoparticles has been addressed in numerous studies. Most of the work reported to date requires high cost, energy intensive approaches such as ultracentrifugation and solvent evaporation to recover the particles. At this point of time, when green science is beginning to make a real impact, it is vital to achieve efficient and effective separation and recovery of colloids to provide environmental and economic benefits. This article explores recent advances in strategies for recycling and reusing functional nanomaterials, which indicate new directions in lean engineering of high-value nanoparticles, such as Au and Pd.

Immobilization on a Nanomagnetic Co/C Surface Using ROM Polymerization: Generation of a Hybrid Material as Support for a Recyclable Palladium Catalyst

A novel hybrid material is reported as support for a recyclable palladium catalyst via surface immobilization of a ligand onto Co-based magnetic nanoparticles (NPs). A standard "click" reaction is utilized to covalently attach a norbornene tag (Nb-tag) to the surface of the carbon coated cobalt NPs. The hybrid magnetic nanoparticles are produced by initiating polymerization of a mixture containing both Nb-tagged ligand (Nb-tagged PPh (3)) and Nb-tagged carbon coated cobalt NPs. In turn, the norbornene units are suitably functionalized to serve as ligands for metal catalysts. A composite material is thus obtained which furnishes a loading that is one order of magnitude higher than the value obtained previously for the synthesis of functionalized Co/C-nanopowders. This allows for its application as a hybrid support with high local catalyst concentrations, as demonstrated for the immobilization of a highly active and recyclable palladium complex for Suzuki-Miyaura cross-coupling reactions. Due to the explicit magnetic moment of the cobalt- NPs, the overall magnetization of this organic/inorganic framework is significantly higher than of polymer coated iron oxide nanoparticles with comparable metal content, hence, its rapid separation from the reaction mixture and recycling via an external magnetic field is not hampered by the functionalized polymer shell.