A magnetite-only hydrogel was prepared for the first time by weak base mediated gelation of stable magnetite hydrosols at room temperature. The hydrogel consists of 10 nm magnetite nanoparticles linked by interparticle Fe-O-Fe bonds and has the appearance of a dark-brown viscous thixotropic material. The water content in the hydrogel could be up to 93.6% by mass while volume fraction reaches 99%. The material shows excellent biocompatibility and minor cytotoxic effects at concentrations up to 207 μg mL. The gel shows excellent sorption capacity for heavy metal adsorption such as chrome and lead ions, which is 225% more than the adsorption capacity of magnetite nanoparticles. Due to thixotropic nature, the gel demonstrates mechanical stimuli-responsive release behavior with up to 98% release triggered by ultrasound irradiation. The material shows superparamagnetic behavior with a coercivity of 65 emu g at 6000 Oe. The magnetite gels prepared could be used for the production of magnetite aerogels, magnetic drug delivery systems with controlled release and highly efficient sorbents for hydrometallurgy.

A method for supporting palladium nanoparticles on magnetically separable organosilica nanoparticles functionalized with ionic liquid groups is described. The system was prepared by sol–gel condensation of two silica precursors: tetraethyl orthosilicate (TEOS) and bis-silylated ionic liquid monomer, on hydrophobic magnetic nanoparticles modified with oleate groups. The support of palladium nanoparticles on the magnetic organo-silica hybrid nanoparticles was achieved by adsorbing palladium salts (Na2PdCl4) on their surface via ion exchange with the ionic liquid groups, followed by reduction with sodium borohydride. The resulted system was applied in three different catalytic transformations: carbonylation of iodoarenes and Heck and Suzuki coupling reactions. The catalyst demonstrated high catalytic activity and was easily separated from the reaction mixture by applying an external magnetic field. The catalyst was recycled over five times without showing a significant loss in its activity.

The preparation of various bis‐N‐heterocyclic carbene (bis‐NHC) complexes of rhodium and their application in the hydroaminomethylation of vinyl arenes was investigated. Various reaction parameters such as solvent, temperature, and pressure were tested, and the optimized protocol was applied to a wide variety of vinyl arenes and amines to afford the corresponding amines in good yields with high selectivity towards the branched product. The bis‐NHC‐based catalyst demonstrated superior reactivity and selectivity compared to catalysts containing bidentate phosphine or monodentate NHC ligands. A triethoxysilyl‐functionalized bis‐NHC ligand was immobilized on magnetic nanoparticles and then utilized to bind a rhodium catalyst. The resulting catalytic system was successfully employed in hydroaminomethylation reactions. The catalyst exhibited excellent reactivity, high selectivity, and was simply recovered from the reaction medium by applying an external magnetic field.

The preparation of magnetically separable silica microcapsules that incorporate in their inner shell a chiral catalyst and their application in asymmetric transfer hydrogenation reactions are described. The preparation method is based on the emulsification of an oil phase containing chloroform, a modified Noyori Ru‐TsDPEN catalyst, tetraethoxysilane (TEOS), and hydrophobic magnetic nanoparticles in water in the presence of an appropriate surfactant, followed by an interfacial polycondensation process under basic conditions to generate a silica shell around the oil droplets. The resulting catalytic microreactors can be considered a “quasi‐homogeneous” system because the immobilized chiral catalyst reacts in a homogeneous zone, the microcapsule core filled with an organic solvent. The catalytic activity was tested in the asymmetric transfer hydrogenation of ketones in an aqueous medium. The catalytic reactions took place only in the presence of surfactants. In addition, the judicious selection of the surfactant plays a crucial role in enhancing the reaction progress through the emulsion‐solid transfer (EST) approach. The catalytic activity of the Ru‐TsDPEN catalyst immobilized within the silica microcapsules was superior to the same catalyst supported on silica microspheres or linked to the backbone of a silica sol–gel matrix, which indicates the importance of the homogeneous zones for the reactions.

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