Synthesis and characterization of Co (III) salen complex immobilized on cobalt ferrite‐silica nanoparticle and their application in the synthesis of spirooxindoles

Synthesis of COF-SO3H immobilized on manganese ferrite nanoparticles as an efficient nanocomposite in the preparation of spirooxindoles

The synthesis of sulfonamide-functionalized magnetic porous nanocomposites is highly significant in chemistry due to their exceptional properties and potential as catalysts. COFs are a new class of organic porous polymers and have significant advantages such as low density, high chemical and thermal stability, and mechanical strength. Therefore, we decided to synthesize COFs based on magnetic nanoparticles, by doing so, we can also prevent the agglomeration of MnFe2O4. MnFe2O4@COF-SO3H possesses a large specific surface area, supermagnetism, and is acidic, making it an optimal catalyst for organic reactions. This particular catalyst was effectively employed in the green and rapid synthesis of various spiro-pyrano chromenes, while several analytical techniques were utilized to analyze its structural integrity and functional groups. The role of a specific site of MnFe2O4@COF-SO3H was confirmed through different control experiments in a one-pot reaction mechanism. It was determined that MnFe2O4@COF-SO3H acts as a bifunctional acid-base catalyst in the one-pot preparation of spirooxindole derivatives. The formation of a spiro skeleton in the multicomponent reaction involved the construction of three new σ bonds (one C-O bond and two C-C bonds) within a single process. The efficiency of the MnFe2O4@COF-SO3H complex is investigated in the synthesis of spirooxindoles of malononitrile, and various isatins with 1,3-dicarbonyles. The nanocatalyst demonstrated excellent catalytic activity that gave the corresponding coupling products good to excellent yields. Furthermore, the heterogeneous magnetic nanocatalyst used in this study demonstrated recoverability after five cycles with minimal loss of activity.

Worldwide research on extraction and recovery of cobalt through bibliometric analysis: a review

Cobalt is a strategic and critical mineral whose demand is expected to grow rapidly. This study aims to provide a comprehensive summary of cobalt extraction and recovery research from 2012 to 2021 in the form of bibliometric analysis. The work was based on the Science Citation Index Expanded (Web of Science) and carried out using the InCites of Clarivate for bibliometric data analysis and the software VOSviewer for science mapping. By analyzing a dataset of 4967 publications, the most influential journals, countries, authors, institutions, and publications were identified, and the keyword co-occurrence networks were mapped. The China mainland produced the most publications, while the USA had the highest average number of citations per publication and the UK was the most collaborative with other countries. The keyword analysis shows that the research hotspots gradually shifted over time from early means and methods for determination of cobalt in solution to recovery of cobalt from spent lithium batteries, smelting slag, copper-cobalt ore, etc. The research will be focused on further improvement and optimization of the separation, extraction, and recovery processes of cobalt from spent batteries in recent and future years, and three approaches were promoted to facilitate economization and industrialization of the processes in this field.

Collagen-coated superparamagnetic iron oxide nanoparticles as a sustainable catalyst for spirooxindole synthesis

In this work, a novel magnetic organic–inorganic hybrid catalyst was fabricated by encapsulating magnetite@silica (Fe₃O₄@SiO₂) nanoparticles with Isinglass protein collagen (IGPC) using epichlorohydrin (ECH) as a crosslinking agent. Characterization studies of the prepared particles were accomplished by various analytical techniques specifically, Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer−Emmett−Teller (BET) analysis. The XRD results showed a crystalline and amorphous phase which contribute to magnetite and isinglass respectively. Moreover, the formation of the core/shell structure had been confirmed by TEM images. The synthesized Fe₃O₄@SiO₂/ECH/IG was applied as a bifunctional heterogeneous catalyst in the synthesis of spirooxindole derivatives through the multicomponent reaction of isatin, malononitrile, and C-H acids which demonstrated its excellent catalytic properties. The advantages of this green approach were low catalyst loading, short reaction time, stability, and recyclability for at least four runs.

Selective oxidation of alcohols and sulfides via O2 using a Co(ii) salen complex catalyst immobilized on KCC-1: synthesis and kinetic study

The aim of this study was to immobilize a Co(ii) salen complex on KCC-1 as a catalyst that can be recovered (Co(ii) salen complex@KCC-1). Field-emission transmission electron microscopy, FT-IR spectroscopy, thermogravimetric analysis, elemental analysis, atomic absorption spectroscopy, and XRD were used to confirm the structure and chemical nature of Co(ii) salen complex@KCC-1. The oxidation efficiency was obtained for an extensive range of sulfides and alcohols using this sustainable catalyst, alongside O₂ as an oxygen source and isobutyraldehyde (IBA) as an oxygen acceptor, with superior selectivity and conversion for the relevant oxidation products (sulfoxides and ketones or aldehydes) under moderate conditions. The μ-oxo and peroxo groups on the ligands of the Co complex appeared to be responsible for the superior activity of the catalyst. Essential factors behind the oxidation of alcohol and sulfoxides were investigated, including the catalyst, solvent, and temperature. In this paper, molecular oxygen (O₂) was used as a green oxidant. Furthermore, kinetic studies were conducted, revealing a first-order reaction for the oxidation of both benzyl alcohol and sulfide. The reaction progressed at mild temperature, and the catalyst could be easily recovered and reused for numerous consecutive runs under the reaction conditions, without any substantial reduction in the functionality of the catalytic system.