Recent advances in the application of magnetic nanocatalysts in multicomponent reactions

Recently, the preparation and applications of magnetic nanostructures have attracted increasing attention in nanocatalysis studies, and magnetic nanoparticle (MNP) functionalized catalysts have been applied in important reactions such as Suzuki-Miyaura and Heck couplings. The modified nanocomposites demonstrate significant catalytic efficiency and excellent benefits in the context of catalyst recovery methods. This review discusses the recent modified magnetic nanocomposites in the field of catalytic applications along with the synthetic processes that are usually employed.

Magnetic Separation of Oxoacid of Boron from Salt-Lake Brine by Synergistically Enhanced Boron Adsorbents of Glucose-Functionalized SiO2 and Graphene

The adsorption separation and extraction of low-concentration boron from salt-lake brine have great significance. Magnetic separation avoids the problem of adsorbent granulation and improves the usage efficiency. The silicon-based adsorbents have attracted interest due to their superior acid and alkali resistance, in which polyhydroxy graphene enhances the adsorption of boron ions. Herein different boron adsorbents, derived by magnetic separation, were developed and characterized by SEM, TEM, XPS, VSM, FT-IR, and XRD analysis. The adsorption-desorption performance of boron adsorbents with different compositions was evaluated. The isotherms and kinetics parameters of the boron extraction were evaluated based on adsorption-desorption tests. The graphene-based magnetic adsorbent (Go-Fe3O4@SiO2@mSiO2-Glu) registered a high boron adsorption capacity of 23.90 mg/g at pH = 9 in the boron solution and 24.84 mg/g for East Taigener salt-lake brine. The Na+, Mg2+, Ca2+, and Cl− ions have little interference with the boron adsorption. The adsorbents exhibit magnetic separation performance and good cycle life. The results showed that acid-alkali desorption solution has little effect on the adsorbents, and the composite of graphene enhances the adsorption of boron ions. The adsorbents developed in this study are promising to recover boron from low-concentration boron-containing salt-lake brines.

Click synthesis of 1,2,3-triazoles using copper iodide nanoparticles anchored poly(sulfonamide-thiazole) modified layered double hydroxides/chitosan nanocomposite

Click synthesis is a class of biocompatible small molecule reactions commonly used in bioconjugation. This research presents a recyclable environmentally-friendly catalyst for 1,2,3-triazoles. To this end, we immobilized poly sulfonamide-thiazole (PST), a new group of sulfonamides, on the surface of layered double hydroxides/chitosan (LDH@CS). Afterward, it was decorated using copper iodide nanoparticles (CuI NPs). LDH@CS@PST/Cu was characterized various techniques, including HNMR, ¹³CNMR, FE-SEM, FT-IR, XRD, EDX, ICP-OES, and TGA/DTA. Overall, the results revealed that LDH@CS@PST/Cu is a promising green efficient for the domino reaction of phenacyl bromides with phenylacetylene and sodium azide.

Magnetic UiO-66 functionalized with 4,4'-diamino-2,2'-stilbenedisulfonic as a highly recoverable acid catalyst for the synthesis of 4H-chromenes in green solvent

According to 4H-chromenes importance, we synthesized a novel magnetic UiO-66 functionalized with 4,4′-diamino-2,2′-stilbenedisulfonic as an efficient and reusable solid acid catalyst for synthesizing 4H-chromene skeletons via a one-pot three components reaction in a green solvent. The structure of the synthesized catalyst was confirmed by various techniques including FT-IR, XRD, BET, TGA, TEM, EDX, and SEM, and also the product yields were obtained in 83–96% of yields for all the reactions and under mild conditions. The reported procedure presents an environmentally friendly approach for synthesizing a significant number of 4H-chromene derivatives. Correspondingly, MOF-based catalyst makes it easy to separate from reaction media and reuse in the next runs.

Recent Advances in Copper-Based Solid Heterogeneous Catalysts for Azide-Alkyne Cycloaddition Reactions

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is considered to be the most representative ligation process within the context of the "click chemistry" concept. This CuAAC reaction, which yields compounds containing a 1,2,3-triazole core, has become relevant in the construction of biologically complex systems, bioconjugation strategies, and supramolecular and material sciences. Although many CuAAC reactions are performed under homogenous conditions, heterogenous copper-based catalytic systems are gaining exponential interest, relying on the easy removal, recovery, and reusability of catalytically copper species. The present review covers the most recently developed copper-containing heterogenous solid catalytic systems that use solid inorganic/organic hybrid supports, and which have been used in promoting CuAAC reactions. Due to the demand for 1,2,3-triazoles as non-classical bioisosteres and as framework-based drugs, the CuAAC reaction promoted by solid heterogenous catalysts has greatly improved the recovery and removal of copper species, usually by simple filtration. In so doing, the solving of the toxicity issue regarding copper particles in compounds of biological interest has been achieved. This protocol is also expected to produce a practical chemical process for accessing such compounds on an industrial scale.

N-heterocyclic silylene stabilized monocordinated copper(i)–arene cationic complexes and their application in click chemistry

Herein, we report N-heterocyclic silylene and N-heterocyclic carbene supported monocoordinated cationic Cu(i) complexes with unsymmetrical arenes (toluene and m-xylene], their reactivity and catalytic application in CuAAC reactions.

Immobilized copper nanoparticles on nitrogen-rich porous activated carbon from egg white biomass: a robust hydrophilic–hydrophobic balance catalyst for click reaction

Nitrogen-rich porous carbon (NAC) material was synthesized from egg white biomass via pyrolysis, followed by chemical activation with KOH. Then, the copper nanoparticles were immobilized on the surface of the NAC by chemical reduction method.