Efficient Recyclable Catalyst Research Articles

The synthesis of Fe3O4@SiO2-NNO-CuII nanocatalyst and investigation of its application in the synthesis of imidazo[1,2-a]pyridines

In this study, a tridentate Schiff base ligand obtained from the condensation of salicylaldehyde and 3-amino-1,2,4 triazole was covalently immobilized on the surface of 3-chloro-trimethoxysilane-functionalized magnetic nanoparticles. This nitrogen and oxygen-rich compound provides donor arms for the coordination of copper ions. The prepared nanocatalyst (Fe3O4@SiO2-NNO-CuII) has been characterized by various techniques including FT-IR, EDX, SEM, VSM, XRD and ICP analysis and used as an efficient recyclable catalyst for the synthesis of imidazo[1,2-a]pydidines. Imidazo[1,2-a]pyridine products were obtained through the coupling reaction of substituted benzaldehydes, 2-aminopyridine derivatives and phenylacetylene under solvent-free conditions in high yields and short reaction times.

Fe3O4@Sal-cu as a highly efficient magnetic nano-catalyst for the synthesis of 2-substituted benzimidazoles under ultrasonic irradiation and solvent free condition

Fe3O4@propyl-semicarbazide-salicyl aldehyde-Cu (Fe3O4@sal-Cu) nanocatalyst was synthesized and characterized by several methods including XRD, SEM, EDX, VSM and FT-IR analyses. The Fe3O4@sal-Cu has been used as an efficient recyclable magnetic catalyst for the preparation of benzimidazoles. The catalyst was conveniently separated from the reaction mixture by an external magnet, and could be reused without any considerable change in catalytic activity.

Anions mediated electron-rich metalloporphyrin ionic framework as recyclable catalyst for conversion of urea into cyclic carbonates

As CO2 typical derivative, urea has the potential to be uniquely economical and green raw materials in generating cyclic carbonates via alcoholysis. Nonetheless, the existing processes for obtaining cyclic carbonates from urea alcoholysis reaction pose considerable challenges in achieving efficient catalyst recycling. Functional organic heterogeneous compounds are emerging materials for catalysis and enhanced reusability due to their large number of coordination sites, but they still fall short of effectively modulating the charge distribution of metal ions. Herein, drawing inspiration from the capacity of ionic liquids (ILs) to effectively control the distribution and transfer of spatial charges within materials, metalloporphyrin ionic framework catalysts were developed by combining metal ions and ILs for the transformation of urea into cyclic carbonates. This heterogeneous catalyst, featuring an adjustable structure and stable metal coordination sites on its surface, exhibits remarkable stability, resulting in a 2.7-fold reduction in catalyst dosage compared to other reported supported catalysts. Based on detailed experiments and DFT calculations, this tunable performance can be mainly explained by the effect of porphyrin zinc (II) and IL anions via molecular engineering. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and available urea using an efficient organic heterogeneous catalyst.

Preparation and Characterization of Nickle-based Nanocatalyst for the Regioselective Synthesis Triazole Derivatives and Antimicrobial Study

Abstract: In this research, poly (4-vinyl pyridine)-supported nickel oxide nanoparticles (P4VP-NiO nanocatalyst) as an efficient recyclable catalyst have been prepared and used for the regioselective synthesis of triazole derivatives. The nanocatalyst we characterized by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), thermogravimetric analysis (TGA), inductively coupled plasma (ICP), and brunauer-emmett-teller (BET) surface area analysis. The most important advantages of using poly (4-vinylpyridine)-nickel oxide nanocatalysts in these reactions are the short reaction time, cost-effectiveness, easy recycling of the catalyst, and high yield of the product. Also, the antimicrobial properties of the new triazole derivatives have been studied.

AgNPs/lignin-aminated polyol/polyvinyl alcohol sponges as efficient recyclable catalysts for organic pollutants degradation

AgNPs/lignin-aminated polyol/polyvinyl alcohol sponges as efficient recyclable catalysts for organic pollutants degradation

Polymer-Grade Bio-Monomers from Oleochemicals by Combining Homogeneous Catalysis and Selective Product Crystallization in an Integrated Process

The homogeneously catalyzed methoxycarbonylation of bio-based methyl 10-undecenoate (C11-DME) produces linear 1,12-dimethyl dodecanedioate (l-C12-DME). Subsequent selective product crystallization from the reaction mixture with downstream filtration and washing allows for the generation of the bio-monomer in polymer grade quality (>99.9%). This effective purification enables its direct use, e.g., for bio-based polyamides, without further purification. It separates the expensive homogeneous catalyst dissolved in the liquid phase in its active state for efficient catalyst recycling. We present the complex interactions of process parameters regarding reaction and crystallization-based purification in an integrated catalyst recycling process. Furthermore, we demonstrate that purification of l-C12-DME with >99.9% purity over multiple consecutive recycling runs is possible. However, as the crystallization is highly sensitive towards changing concentrations of by-products and particularly unreacted substrates, this high purity is only achieved by maintaining a stable composition in the reaction mixture using a newly developed system for precise conversion control in the reaction step.

Synthesis of Cu/Co-hybrid MOF as a multifunctional porous compound in catalytic applications, synthesis of new nanofibers, and antimicrobial and cytotoxicity agents

Several biological properties of metal–organic frameworks (MOFs) and fiber compounds have been reported, and combinations of these structures can have unique properties. In this study, copper-containing and cobalt-containing MOF nanostructures were synthesized by the ultrasonic technique. Then, novel Cu/Co-hybrid MOF nanostructures were synthesized using the ultrasonic method. Synthesized Cu/Co-hybrid MOF nanostructures were used as a new and efficient recyclable catalyst in the synthesis of pyrano[2,3-c]pyrazole derivatives using the four-component reaction of phenylhydrazine, ethyl acetoacetate, malononitrile, and aldehyde. In the following, novel Cu/Co-hybrid MOF/PVA (poly vinyl alcohol) fiber nanostructures were synthesized by electrospinning and using Cu/Co-hybrid MOF nanostructures and PVA. The structures of the Cu/Co-hybrid MOF nanostructures and the Cu/Co-hybrid MOF/PVA fiber nanostructures were identified and confirmed using BET, TGA, FTIR, SEM, and XRD. In biological studies, the antibacterial, antifungal, and cytotoxicity activities of Cu/Co-hybrid MOF and Cu/Co-hybrid MOF/PVA fiber nanostructures were evaluated. In investigating the catalytic activity of Cu/Co-hybrid MOF, pyrano[2,3-c]pyrazole derivatives were synthesized with higher efficiency and less time than previously reported methods. High antibacterial (against gram-negative and gram-positive strains) and antifungal properties of synthesized Cu/Co-hybrid MOF nanostructures and Cu/Co-hybrid MOF/PVA fiber nanostructures were observed (MIC between 16 and 256 μg/mL), which were higher than some commercial drugs. In the investigation of cytotoxicity activity, the effectiveness on breast cancer cells was studied. The maximum cell proliferation and viability for Cu/Co-hybrid MOF and Cu/Co-hybrid MOF/PVA fiber nanostructures were 38% and 38% higher than the control in a concentration of 200 μg/mL after 48 h. The high catalytic and biological properties of the synthesized nanoparticles can be attributed to the presence of nano-sized bioactive metals and their high specific surface area. The significant physical-chemical properties obtained for synthesized nanoparticles in this study can be related to the desirable synthesis methods, the development of materials with high purity, and the incorporation of hybrid compounds into the nanostructures.

Ultrasound-promoted metal-free homogenous olefins epoxidation and direct conversion of alkenes to cyclic carbonates using catalytic TAIm[X] (X = WO42-, HSO5-) recyclable ionic liquid under mild conditions

TAIm[WO4] and TAIm[HSO5] ionic liquids were prepared and used as efficient solvent and recyclable catalysts for the mild epoxidation of olefins and the domino preparation of cyclic carbonate from alkenes under ultrasound irradiation. H2O2 was used as an oxidant. The physical properties and structure of the ionic liquids were studied by various analytical methods including FTIR, EDX, viscosity, and density measurements. High to excellent yields were obtained for a wide variety of olefins whether aliphatic or aromatic types for the epoxides as well as the conversion of cyclic and terminal olefins to cyclic carbonates at low CO2(g) pressure (∼1 atm.). Moderate CO2(g) solubility in the ionic liquids was found. Also, excellent epoxide-selectivity was obtained for all olefins. Scalability of the method demonstrated a direct scalability for the promising gram scale epoxidation of olefins with at least efficiency loss. The TAIm[WO4] and TAIm[HSO5] ionic liquids could be recycled from the homogenous mixture by a simple solvent-solvent extraction, and reused for at least several times with insignificant activity loss.

Construction of silsesquioxane and phosphinum‐based ionic porous hypercrosslinked polymers for efficient heterogeneous catalytic CO2 cycloaddition

AbstractIn this work, we reported a facile one‐pot route to construct polyhedral oligomeric silsesquioxane (POSS) and phosphonium‐based ionic porous hypercrosslinked polymers (denoted as P‐iPHCPs) with multiple catalytic active sites, which could be regarded as efficient heterogeneous catalysts for the conversion of carbon dioxide (CO2) to highly value‐added cyclic carbonates. The targeted polymers P‐iPHCPs were prepared from a rigid building block octavinylsilsesquioxane (VPOSS) and a low‐cost commercially available organic ionic salt methyltriphenylphosphonium bromide ([Ph3PMe]Br) by the AlCl3‐catalyzed Friedel‐Crafts reaction. The series of polymers P‐iPHCPs that synthesized by different molar ratios of VPOSS to [Ph3PMe]Br possess hierarchical micro/mesoporous structures with high surface areas ranging from 376 to 429 m2 g−1 and behave the flower‐like nano‐morphology. Especially, the desired multiple active sites involved the mixed anions including free Cl−, Br− anions and the in‐situ formed metal‐halogen complex anion [AlCl3Br]− within phosphonium segments, and the enriched POSS‐derived SiOH hydrogen bond donor (HBD) groups that derived from the breakage of POSS cages during the synthetic process. The typical polymer P‐iPHCP‐14 has the aforementioned nucleophilic‐electrophilic multiple catalytic active sites, which was regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO2 with various epoxides into cyclic carbonates under mild conditions.

A Novel Powerful γ-Fe2O3 @ CPTMS - Diethylene Triamine (DETA) @SO3H as a Heterogeneous Nanocatalyst, Recyclable and Efficient via Microwave-assisted for the Synthesis of Benzoxazinone- 4(3H)-one Derivatives in Green Media

Background: In order to synthesize benzoxazin-4 (3H) -one derivatives, a new inorganic- organic super-magnetic nano-hybrid (γ‐Fe2O3@ CPTMS-DETA @SO3H) nanocatalyst of the modified sulfuric acid represents a green and efficient catalyst to perform a three-component condensation reaction between various acyl chlorides, anthranilic acid and acetic anhydride (as cyclization agent), in one-pot and solvent-free conditions under microwave irradiation (4a-q). Introduction: In recent years, one of the most important subjects in synthetic organic chemistry has been green synthesis, which has applied environmentally friendly and efficient methods to synthesize biological derivatives. The use of catalysts has significant advantages, including simple separation and preparation, chemical and thermal stability, and eco-friendly nature and their features such as reusability, low cost, high efficiency and easy operation. Therefore, the mechanism is performed by a non-toxic organic catalyst that uses the chemical reactants and the least energy in accordance based on the least waste and green chemistry. Methods: Sequential addition and one-pot methods were applied to produce benzoxazinone derivatives. In the sequential addition approach, the reaction was begun by adding anthranilic acid and acetic anhydride to the reaction vessel under microwave irradiation and continued by adding γ‐ Fe2O3@ CPTMS-DETA @SO3H as super-magnetic nano-hybrid recyclable green catalysts and the desired acyl chlorides. Results: The main objective of this project was to synthesize benzoxazin-4 (3H) -one derivatives in the presence of super-paramagnetic organic-inorganic nanohybrid particles based on improved sulfonic acid (γ- Fe2O3 @ SiO2 - DETA @ SO3H) as an efficient recyclable heterogeneous catalyst. Conclusion: This paramagnetic nano-organocatalyst was characterized by EDX, VSM, TGA, FESEM, FT-IR, and XRD. Advantages of this catalyst include easy preparation, clear and easy operation, short reaction time (15–30 min), as well as without the use of toxic catalysts. In addition, the catalyst can be separated from the reaction solution using an external magnet by magnetic decantation; it can be recycled up to six times without reducing its activity.

Eggshell powder as an efficient recyclable catalyst generates H2O2 prompted radicals for selective oxidative mineralization of crystal violet dye at room temperature

Eggshell powder (ESP) was explored as a selective heterogeneous catalyst for oxidative degradation of crystal violet (CV) dye in aqueous media in presence of H2O2 at room temperature. Natural but throw-away material ESP as a carbonate (CO32−) source facilitated the formation of carbonate anion radicals in presence of H2O2. Carbonate anion radicals (CO3•−), though a weaker oxidant than ∙OH radical, efficiently served as a selective oxidant. Selective degradation of CV dye in aqueous solution was confirmed from the quenching experiments. Synergistic effects of both the radicals (CO3•− and ∙OH) in the dye degradation process was experimentally verified. At a dose of 10 g/L of ESP, 91% removal of CV (initial concentration: 10 mg/L) was achieved in 60 min. The reaction kinetics followed first order rate model. Intermediate products formed during CV degradation and the extent of mineralization were confirmed from MALDI-TOF-MS and TOC analysis, respectively. The turnover number (TON) and turnover frequency (TOF) were obtained as 2.45 × 10−6 mol per g and 6.81 × 10−10 mol per g per second. A promising reusability was achieved up to seven cycles. The ESP catalyst used in this study was characterized by SEM, FTIR, XRD, XPS, BET surface area analysis, UV–visible DRS, XRF, and pHZPC analyses. The present work offers a novel facile but selective route for CV degradation and opens up newer possibilities for eggshell waste utilization as catalyst.

Ag-Ni alloy nanoparticles decorated reduced graphene oxide nanocomposite as highly efficient recyclable catalyst for the reduction of 4-nitrophenol and methylene blue

Ag-Ni alloy nanoparticles decorated reduced graphene oxide nanocomposite as highly efficient recyclable catalyst for the reduction of 4-nitrophenol and methylene blue

Copper phthalocyanine tetrasulfonic acid (CuPcS) as an efficient recyclable catalyst for aromatic nitration using sodium nitrate

Nitration of aromatic compounds is an important transformation in synthetic organic chemistry. It becomes imperative to design a highly efficient and environmentally friendly protocol for the synthesis of nitro compounds. Towards this goal, we have developed copper phthalocyanine tetrasulfonic acid as a biodegradable and recyclable solid acid catalyst for aromatic nitration. As a result of the reaction performed, it was observed that copper phthalocyanine tetrasulfonic acid has excellent catalytic activity and can also be recycled after completion of the reaction. So this method of aromatic nitration would be more efficient, greener, and safer than the conventional method. This catalyst has been used to nitrate both activated and deactivated aromatic rings under mild conditions, and it has the ability to synthesize nitro compounds sustainably.

Hydrothermally Developed ZnC2O4.2H2O Nanocrystals as Efficient Copper‐free Catalyst for the Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles in Water

AbstractIn this work, we report the synthesis of nanostructured ZnC2O4.2H2O with irregular sheet‐like morphology using a simple hydrothermal procedure. The as‐synthesized ZnC2O4.2H2O nanocrystal (ZnC2O4 NC) is very stable and therefore, explored for the first time as highly efficient recyclable catalyst for the azide‐alkyne cycloaddition (AAC) reaction. Our catalytic protocol is highly efficient and amenable to a variety of aromatic/aliphatic azide and alkyne substrates under mild reaction condition to afford regioselective 1,4‐disubstituted 1,2,3‐triazoles with good to excellent yields. Also, for the one pot synthesis of desired products, the developed method is exceedingly sustainable where azides are formed in‐situ from their respective precursors. Our catalytic results outperformed most of the reported state‐of‐the‐art works involving copper free nanoparticulate and zinc‐based catalysts. All the original features of the recovered catalyst remained intact after 5th catalytic cycle which clearly suggests the efficiency of the Zn‐based stable nanostructured material as alternative copper free catalysts for AAC reactions. The developed methodology could be extended for gram‐scale synthesis of 1,2,3‐triazoles.

Pushing Boundaries—Selective Cooling Crystallization as Tool for Selectivity Compensation and Product Purification Using a Recyclable Pd/Xantphos Catalyst in the Methoxycarbonylation of Methyl 10‐Undecenoate

AbstractThe homogeneously catalyzed methoxycarbonylation of methyl 10‐undecenoate allows for the synthesis of dimethyl 1,12‐dodecandioate as an interesting bio‐based drop‐in alternative for 1,12‐dodecandioic acid as polymer building block. Although the benchmark catalyst system of Pd/1,2‐bis((di‐tert‐butylphosphino)methyl)benzene and methane sulfonic acid is very active and selective, long‐term stability over a potential catalyst recycling is limited. In this work, modifications of this catalyst system in terms of protonation of the ligand and its replenishment during recycling are first investigated, proving that the reaction system is tolerant against minor changes. Finally, the commercially available ligand Xantphos, featuring higher stability but comes with a rather low l:b selectivity of 70:30, is applied. However, through the application of cooling crystallization, 58 g product (52% isolated yield) with an overall purity of 94% is obtained from the crude reaction solution without further treatment and a ∑TON of 4000 after ten reaction runs, while catalyst loss into the product is low.Practical Applications: Selective syntheses on the basis of renewable resources are a powerful tool for the production of value products in terms of green chemistry. Thereby, homogeneous transition metal catalysts are beneficial regarding selectivity. However, their separation and recycling are challenging due to their limited stability. The combination of a stable, commercially available catalyst with a selective purification method allows for isolation and purification from a crude reaction mixture without the need for any auxiliary or further purification steps. In this work, cooling crystallization is applied for subsequent purification of the linear diester dimethyl 1,12‐dodecandioate. Thereby, a lower selectivity from the methoxycarbonylation reaction using the stable Xantphos ligand is compensated and combined with recycling of the homogeneous catalyst. Thus, the development of an integrated process covering a stable catalyst system in the reaction, and high selectivity in the purification is the key toward an efficient homogeneous catalyst recycling.

Grafting Schiff base Cu(II) complex on magnetic graphene oxide as an efficient recyclable catalyst for the synthesis of 4H-pyrano[2,3-b]pyridine-3-carboxylate derivatives

Schiff base Cu(II) complex (Sc–Cu) stabilized on the surface of graphene oxide modified magnetic nanoparticles (GO/Fe3O4) using 3-chloropropyltrimethoxysilane ((MeO)3Si-PrCl) as a linker, (GO/Fe3O4@SPSc-Cu), was prepared, characterized and used as a magnetically separable and reusable heterogeneous catalyst in the multi-component reaction of aldehyde, 3-cyano-6-hydroxy-4-methyl-pyridine-2(1H)-one, and ethyl acetoacetate to afford a series of novel 4H-pyrano[2,3-b]pyridine-3-carboxylate derivatives under solvent-free conditions. The structure of the catalyst (GO/Fe3O4@SPSc-Cu) was characterized by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, transmission electron microscopy (TEM), high resolution TEM (HRTEM), fast Fourier transform (FFT), scanning TEM (STEM), X-ray diffraction (XRD), thermogravimetry/derivative thermogravimetry (TG/DTG), and vibrating sample magnetometer (VSM) analyses. Various spectral analyses such as 1H and 13C NMR, FT-IR and ESI-MS were used to determine the structure of the products. The catalyst demonstrated good to excellent catalytic efficiency for reactions under green conditions using a wide range of substrates. The advantages of this process include a simple reaction set-up, high yield, short reaction time, environmentally friendliness, recyclable catalyst and easy separation of the products. In addition, the catalyst was recovered through magnetic decantation and reused for five consecutive cycles.

Solvent-free synthesis of oleic acid-based wax esters using recyclable acidic deep eutectic solvent

Wax esters have been widely used in cosmetics and pharmaceutical products. Oleic acid wax esters can be used to replace spermaceti oil or jojoba oil. In this work, the acidic deep eutectic solvent (DES) composed of choline chloride and p-toluenesulfonic acid (1:4, mol/mol) was used as an efficient recyclable catalyst for the synthesis of oleic acid-based liquid wax esters through an esterification reaction. The esterification conversion of cetyl alcohol reached 99.1% under the following optimal reaction conditions: 5% DES as catalyst, molar ratio of fatty acid to alcohol of 1.3:1 and reaction temperature of 70 oC for 3h. The catalyst recovery experiments showed that this low-price acidic DES catalyst could be reused five times with uniform activity. Moreover, DES-catalyzed solvent-free esterification could be applied in the preparation of other oleic acid-based wax esters and excellent conversions (> 96%) could be obtained under such mild conditions.

Endeavors on the development of efficient and sustainable supported metal catalysts for chemical synthesis on solid–liquid interfaces

Supported metal catalysts, particularly for precious metals, have gained increasing attention in green synthetic chemistry. They can make metal-catalyzed organic synthesis more sustainable and economical due to easy separation of product with less metal residue, as well as reusability of the high-cost catalysts. Although great effort has been spent, the precise catalytic mechanism of supported metal-catalyzed reactions has not been clearly elucidated and the development of efficient and stable recyclable catalysts remains challenging. This highlight reveals a “molecular fence” metal stabilization strategy and discloses the metal evolution in Pd-catalyzed C–C bond formation reactions using N-heterocyclic carbene (NHC)-functionalized hypercrosslinked polymer support, wherein the polymeric skeleton isolates or confines the metal species involved in the catalytic reactions, and NHC captures free low-valent metal species in solution and stabilizes them on the support via strong metal-support coordination interaction. This strategy creates a novel route for the development of supported metal catalysts with high stability and provides insights into the reaction mechanism of heterogeneous catalysis.

Synthesis, characterization and application of magnetic biochar sulfonic acid as a highly efficient recyclable catalyst for preparation of spiro-pyrazolo[3,4-b]pyridines

Synthesis, characterization and application of magnetic biochar sulfonic acid as a highly efficient recyclable catalyst for preparation of spiro-pyrazolo[3,4-b]pyridines

N-Doped Graphene Supported Cu Single Atoms: Highly Efficient Recyclable Catalyst for Enhanced C-N Coupling Reactions.

Heterogenization of homogeneous catalysis through supported single-atom catalysts (SACs) provided a feasible solution to recycling catalysts while keeping its efficiency in chemical synthesis. In this work, Cu SACs anchored on N-doped graphene (Cu SACs/NG) were prepared and first used for C-N coupling reactions. During the preparation, Cu-N-C structures, including Cu-N4 moieties, were formed in a one-step pyrolysis method. As-prepared Cu SACs/NG exhibited excellent catalytic activity toward C-N coupling reactions with a broad scope of substrates and showed outstanding performance of recycling. Compared with Cu nanoparticles (Cu NPs/NG), the advantages of single-atom catalysts were validated via experimental and theoretical calculations. The enhanced performances were attributed to increasing the number of active sites and increasing the intrinsic activity of each active site. This work provides an alternative synthetic strategy for fabricating atomically dispersed SACs and represents a significant advance for coupling reactions.