Fe3O4@PEG core/shell nanoparticles as magnetic nanocatalyst for acetylation of amines and alcohols using ultrasound irradiations under solvent-free conditions

Nanomagnetic nickel complex based on salicylamide and l-proline ligands as an efficient heterogeneous catalyst for synthesis of tetrazoles

A novel salicylamide-l-proline-nickel(ii) complex, supported on magnetic iron oxide [Fe3O4@salicylamide-l-proline-Ni(ii)], was synthesized through a three-step procedure. This included the functionalization of Fe3O4 with amine groups using glycine as a linker, followed by direct amidation of salicylic acid and its subsequent coordination with Ni(ii) and l-proline as a co-ligand to form the nanomagnetic Ni(ii) complex. The resulting catalyst was comprehensively characterized by several techniques. The catalyst exhibited outstanding catalytic performance in the homoselective synthesis of 5-substituted-1H-tetrazoles from benzonitriles. Notably, it demonstrated excellent recyclability, maintaining high efficiency over eight reaction cycles. The use of a low-cost linker, ligand, and complex catalyst, combined with easy magnetic separation, minimal leaching, and scalability, renders this approach both environmentally sustainable and economically advantageous compared to traditional Ni-based methods.

Application of MIL-101(Cr) for biofuel dehydration and process optimization using the central composite design method

Nowadays, researchers from various fields are aiming to replace petro-based and other fossil fuels with green and renewable alternatives. One of the potential candidates, requiring a highly pure reactant, is biofuel. The use of alcohol-containing water as a reactant can lead to different types of problems including the generation of side reactions, hydrolysis, equilibrium shifts, catalyst deactivation and process complexity. A metal-organic framework, MIL-101(Cr), was successfully synthesized using the hydrothermal method and subsequently employed for the dehydration of a standard biofuel. With this goal in mind, we aimed to optimize the effects of operational parameters-specifically, initial water concentration, adsorbent dosage, and temperature-using the central composite design (CCD) method, while also analyzing their behaviors by applying variance analysis. To predict the process behavior, we propose a refined quadratic equation under various conditions, achieving an R 2 value of 95.26. The results showed that the process was more influenced by temperature variations than the other two parameters. The optimal conditions were predicted with an initial concentration of 1.41, catalyst dosage of 0.14, and a temperature of 302.5 K, resulting in a capacity of 1349.72 and a desirability value of 0.95. Additionally, the synthesized MIL-101(Cr) was characterized using XRD, SEM, DSC/TGA, and N2 physisorption techniques. The results indicated that the particles possessed microporous windows and mesoporous cages, exhibiting a uniform octahedral shape with an average size ranging between 200 and 500 nm.

Magnetic nanoparticles modified with a copper(i) complex as a novel and efficient reusable catalyst for A3 coupling leading to C-N bond formation

Propargylamines are an important and valuable family of nitrogen-containing compounds with many applications in the fields of medical, industrial, and chemical processes. One-pot multicomponent A3 coupling reactions of aldehydes, amines, and alkynes in the presence of transition metals as catalysts is an efficient strategy for preparing propargylamines. In this study, we fabricated a novel magnetically reusable copper nanocatalyst [Fe3O4-BIm-Pyrim-CuI] through the immobilization of the copper(i) complex on the surface of the magnetic nanoparticles modified with benzimidazole-pyrimidine ligand and evaluated its catalytic activity in the preparation of propargylamines through one-pot multicomponent A3 coupling reactions of aldehydes, amines, and alkynes. Under this catalytic system, aryl substrates with both electron-donating and electron-withdrawing substituents also gave the desired products in excellent yields under standardized conditions. The Fe3O4-BIm-Pyrim-CuI catalyst was easily separated using an external magnet, and the recovered catalyst was reused in 8 cycles without significant loss of activity.

Phosphomolybdic acid hydrate encapsulated in MIL-53 (Fe): a novel heterogeneous heteropoly acid catalyst for ultrasound-assisted regioselective nitration of phenols

In this study, a heterogeneous catalyst, PMA@MIL-53 (Fe) (MIL ⇒ Matériaux de l'Institut Lavoisier), has been used to replace the usual mineral acids such as sulfuric acid. A wide variety of nitration methods require the use of a mixture of acids such as concentrated nitric acid and sulfuric acid, which result in producing a large amount of acidic waste. During recent years, the use of the heterogeneous system for the nitration of aromatic compounds has been highly considered and used by chemists due to some specific advantages, i.e. easy separation of the product from the reaction mixture, the possibility of recycling and reusing the catalyst, etc. Herein, the catalyst was synthesized using a metal-organic framework and a heteropoly phosphomolybdic acid. The PMA@MIL-53 (Fe) was prepared using a similar method of MIL-53 (Fe) synthesis. Afterwards, FeCl3·6H2O and 1,4-benzene dicarboxylic acid (BDC) in a dimethylformamide solution were placed in an ultrasound bath and, then, HPA (heteropoly acid) was added to the reaction mixture. The PMA (phosphomolybdic acid) encapsulation in MIL-53 (Fe) was confirmed using various analysis. Under optimal conditions, the catalytic activity of PMA@MIL-53 (Fe) was evaluated in nitration of phenol under ultrasonic waves. Besides, the ratio of the two products of ortho and para was obtained using GC. Optimum conditions were reached after 15 minutes, in such a way that the loaded PMA was 0.02 g under optimal conditions, the efficiencies of ortho-nitrophenol and para nitrophenol were 54.98 and 45.01, respectively.