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A new nitrogen ligand, i.e. 1,3-di-( o- aminophenoxy)-2-propyl propargyl ether (DPPE), has been synthesized and characterized. Magnetic mesoporous silica composite (MNP@SiO 2 -SBA) was obtained via embedding magnetite nano-particles (MNPs) between SBA-15 channels. DPPE palladium dichloride (MNP@SiO 2 -SBA-DPPE-Pd(II)) was then prepared via click chemistry and fully characterized. The activity and recyclability of supported magnetic Pd(II) catalyst were evaluated in Heck coupling reaction after optimizing the optimal reaction conditions including solvent, amount of catalyst, base and temperature. Aryl iodides and aryl bromides showed enhanced activity compared to those of aryl chlorides in the Heck reaction. The catalyst was easily separated magnetically, reused in five runs sequentially, and no significant loss of activity was observed. Graphic Abstract

IRMOF-3 with a high surface area prepared by a hydrothermal method was used for deposition of Pd(OAc) 2 on IRMOF-3 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry, scanning electron microscopy, transmission electron microscopy combined with energy dispersive X-ray analysis, wide angle X-ray diffraction spectroscopy and X-ray photoelectron spectroscopy. The prepared porous catalyst was effectively used in the Heck coupling reaction in the presence of an organic base. The reaction parameters such as the type of base, amounts of catalyst and solvents, temperature were optimized. The catalyst was then easily separated, washed, and reused 4 times without significant losses of catalytic activity. Graphical Abstract

Magnetic particles were prepared by a hydrothermal method and then successively covered by Metal–Organic-Frameworks MIL-101-NH 2 with a high surface area. This was followed by deposition of Pd(OAc) 2 on Fe 3 O 4 –NH 2 @MIL-101-NH 2 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry (TGA), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), wide-angle X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared magnetic catalyst was effectively used in the Heck coupling reaction in the presence of an inorganic base. The reaction parameters such as the base type, amounts of catalyst and solvents, temperature, and substrates ratios were optimized. The catalyst was then magnetically separated, washed, and reused 7 times without losing significantly catalytic activity. Graphic Abstract

Mesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd nanoparticles onto it. The synthesized materials were characterized with infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen physisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP-OES). The catalyst was effectively used in the Mizoroki–Heck coupling reaction of various reactants in the presence of an organic base giving the desired products in a short reaction time and with small catalysts loadings. The reaction parameters such as the base type, amounts of catalyst, solvents, and the temperature were optimized. The catalyst was easily recovered and reused at least seven times without significant activity losses.Graphic Abstract

2-(2-Pyridyl)benzimidazole (PyBzIm) was supported onto magnetic mesoporous silica, Fe3O4@SiO2@SBA-15 via the click chemistry. The supported ligand was treated with Na2PdCl4 in methanol to afford Fe3O4@SiO2@SBA-PyBzIm-Pd(II) as a magnetically retrievable supported catalyst. The catalyst was fully characterized by conventional methods. X-ray photoelectron spectroscopy (XPS) studies confirmed some C = N nitrogen atoms interact with palladium in the + 2 oxidation state. The prepared catalyst was found to catalyze the aerobic oxidation of benzyl alcohols and benzaldehydes to the corresponding benzoic acids, and excellent conversions were obtained. The magnetic catalyst showed a very low metal leaching (3.9%) in the first run. Fe3O4@SiO2@SBA-PyBzIm-Pd(II) was then treated with aqueous NaBH4 to give Fe3O4@SBA-PyBzIm-Pd(0). The obtained catalyst was found to catalyze the transfer hydrogenation of nitroarenes to the corresponding anilines in the presence of hydrazine, and excellent yields were obtained. The prepared catalysts present an excellent recycling efficiency over seven consecutive runs without significant loss of catalyst reactivity.Graphical abstract

Removal of heavy metal ions such as cadmium, lead, chromium, and iron from industrial wastewater is one of the most critical environmental problems. In this research, natural and low-cost adsorbents like the tangerine peel, bovine gut, tea waste, and sunflower seed hull were used for adsorption of heavy metals, such as chromium and iron, from contaminated solutions. The effects of environmental factors such as contact time, pH, the amount of adsorbent dose, and the initial concentration of metal ions in synthetic solution were investigated to obtain optimal conditions for the adsorption of heavy metal ions. For separation of chromium metal ion from aqueous solution, tea waste, tangerine peel, bovine gut, and sunflower seeds hull showed adsorption capacity of 85%, 51%, 46%, and 34%, respectively, while for the adsorption of iron (III), the adsorption capacities of tea waste, bovine gut, tangerine peel, and sunflower seeds hull were 96%, 96%, and 87%, respectively. The adsorption isotherms were in decent correlation with the Langmuir and Freundlich isotherm models. The adsorption kinetics of iron and chromium has a proper validation with the pseudo-second-order kinetic model. The BET and FTIR analyses were also reported to investigate the adsorption properties. This study suggests these adsorbents as low-cost and economical materials for the adsorption of chromium and iron ions with a high adsorption rate.

A thorough experimental optimization of supported ionic liquid catalyst (SILCA) was performed in order to obtain a stable and efficient catalyst for the Heck reaction. Out of fifteen proposed structures, propyl imidazolium bromide-tetramethylguanidinium pentanoate modified SiO2 loaded with PdCl2 appeared to be the most stable and to have a good activity in the reaction between butylacrylate and iodobezene, resulting in a complete conversion in 40 min at 100 °C, in four consecutive experiments. This study elucidated on the stability of the catalytic system with an ionic liquid layer during the catalyst synthesis but also under reaction conditions. In the bis-layered catalyst, the imidazolium moiety as a part of internal layer, brought rigidity to the structure, while in external layer pentanoic acid gave sufficiently acidic carboxylic group capable to coordinate 1,1,3,3-tetramethylguanidine (TMG) and thus, allow good dispersion of Pd nanoparticles. The catalyst was characterized by means of XPS, FT-IR, TEM, ICP-OES, ζ-potential, EDX, TGA, and 13C NMR. The release and catch mechanism was observed, whereas Pd re-deposition can be hindered by catalyst poisoning and eventual loss of palladium.

A new nitrogen ligand, i.e. 1,3-di-(o-aminophenoxy)-2-propyl propargyl ether (DPPE), has been synthesized and characterized. Magnetic mesoporous silica composite (MNP@SiO.sub.2-SBA) was obtained via embedding magnetite nano-particles (MNPs) between SBA-15 channels. DPPE palladium dichloride (MNP@SiO.sub.2-SBA-DPPE-Pd(II)) was then prepared via click chemistry and fully characterized. The activity and recyclability of supported magnetic Pd(II) catalyst were evaluated in Heck coupling reaction after optimizing the optimal reaction conditions including solvent, amount of catalyst, base and temperature. Aryl iodides and aryl bromides showed enhanced activity compared to those of aryl chlorides in the Heck reaction. The catalyst was easily separated magnetically, reused in five runs sequentially, and no significant loss of activity was observed.

This paper reports the synthesis and characterization of SBA-15/melamine–formaldehyde nanocomposite impregnated with Pd(0) nanoparticles, SBA-15@Pr-NH 2 /MF-Pd(0). The catalytic ability of the prepared material was shown in the reduction in aromatic nitro compounds in the presence of hydrazine hydrate as a hydrogen source. The reaction parameters, including the amount of hydrazine, solvent, and catalyst dosage, were optimized. It was observed that SBA-15@Pr-NH 2 /MF-Pd(0) acts as a highly active, operationally simple, and safe catalyst under optimal reaction conditions. The reactions proceed in EtOH within a short reaction time, and excellent yields/TOFs were obtained for a wide range of aromatic nitro compounds. It was shown that the prepared catalyst is stable and could be reused in consecutive runs after separation.

A nitrogen ligand, i.e. 1,3-di-(o-aminophenoxy)-2-propyl propargyl ether (DPPE), has been synthesized and characterized. Magnetic mesoporous silica composite (MNP@SiO2-SBA) was obtained via embedding magnetite nano-particles (MNPs) between SBA-15 channels. DPPE palladium dichloride (MNP@SiO2-SBA-DPPE-Pd(II)) was then prepared via click chemistry and fully characterized. The Hiyama reaction conditions including solvent, amount of catalyst, base and temperature were optimized for the prepared catalyst. The activity and recyclability of supported magnetic Pd(II) catalyst were evaluated under the optimal reaction conditions. The catalyst was easily separated magnetically, reused in five runs sequentially, and no significant loss of activity was observed.