Recoverable Catalyst Research Articles

A General Enantioselective C-H Arylation Using an Immobilized Recoverable Palladium Catalyst.

We herein report a general and efficient enantioselective C-H arylation of aryl bromides based on the use of BozPhos as the bisphosphine ligand and SP-NHC-PdII as recoverable heterogeneous catalyst. By exploiting the "release and catch" mechanism of action of the catalytic system, we used BozPhos as a broadly applicable chiral ligand, furnishing high enantioselectivities across all types of examined substrates containing methyl, cyclopropyl and aryl C-H bonds. For each reaction, the reaction scope was investigated, giving rise to 30 enantioenriched products, obtained with high yields and enantioselectivities, and minimal palladium leaching. The developed catalytic system provides a more sustainable solution compared to homogeneous systems for the synthesis of high added-value chiral products through recycling of the precious metal.

An Efficient One-Pot Synthesis of Octahydroquinazolinone Derivatives Using Magnetic Cobalt Ferrite Catalyst

In this work, octahydroquinazolinone derivatives were synthesized using magnetic cobalt ferrite nanoparticles using oxalate precursor method. The XRD pattern and IR spectrum confirmed the formation of single segment cubic spinel cobalt ferrite. The average size of the crystallites was determined to be 26.599 nm, while the lattice constant was found to be 8.365 Å. A fine spherical CoFe2O4 particles with some quantity of aggregation may be observed within the SEM and TEM images. Nano spinel cobalt ferrite nanoparticles is a easily synthesized, non-toxic, less expensive, effortlessly magnetically recoverable and green catalyst for the synthesis of octahydroquinazolinone derivatives through the condensation of aromatic aldehydes with urea or thiourea and dimedone. The advantages of this technique are quick reaction time, ease of product isolation and high yields.

Fe3O4@SiO2@BHA-Cu(II) as a new, effective, and magnetically recoverable catalyst for the synthesis of polyhydroquinoline and tetrazole derivatives

Fe3O4@SiO2@BHA-Cu(II) as a new, effective, and magnetically recoverable catalyst for the synthesis of polyhydroquinoline and tetrazole derivatives

Organocatalyzed Mannich reaction: Electrochemically synthesized prolinated carbon dots vs. prolinated graphene oxide

Background L-Pro was previously used as an organocatalyst in the Mannich reaction under homogeneous conditions; a recoverable catalyst could be useful; this is the first report on the application of prolinated carbon dots to the Mannich reaction. Methods Prolinated carbon dots were synthesized electrochemically using a bottom-up approach; they were characterized and used in the Mannich reaction in water using only a slight excess of ketone; for a useful comparison, L-proline decorated graphene oxide was synthesized. Results The characterization of carbon dots and functionalized graphene oxide confirmed the presence of L-Pro on their surface; their use in the Mannich reaction gave good yields when carrying out the reaction in water; a possible recycle of the catalyst was demonstrated. Conclusions Both electrochemically synthesized prolinated carbon dots and prolinated graphene oxide acted as organocatalysts in the Mannich reaction. Higher yields were obtained using L-Pro-CDs obtained under galvanostatic conditions.

Simple synthesis of the novel Cu-CYA coordination polymer and its application as a green and recoverable catalyst for the asymmetric Hantzsch synthesis of polyhydroquinoline derivatives

This study designed and fabricated a novel, Cu-containing coordination polymer system via a hydrothermal reaction of copper salt with cyanuric acid as a tridentate ligand. The prepared coordination polymer was investigated by XRD, BET, SEM, EDS, FT-IR, and X-ray mapping techniques. The prepared Cu-CYA coordination polymer exhibits good catalytic activity in the synthesis of polyhydroquinolines under gentle reaction conditions in short reaction times. Furthermore, this nanostructure afforded a few benefits, which include excessive yields, short reaction times, stability, easy methodology, easy workup, and greener situations. Furthermore, the activity of the recycled catalyst was examined for at least five cycles with a negligible loss of its activity.

Preparation of GO/Cys-Cu(II) as a novel, effective and recoverable catalyst for the multi component synthesis of spirooxindoles under mild conditions

Modified graphene oxide (GO/CPTES/Cys-Cu(II)) was prepared as a reusable catalyst and characterized by various analytical and spectroscopic methods, including Fourier transform spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and inductively coupled plasma (ICP) techniques. Obtained results from demonstrated the existence of cystein/Cu(II) on the MWCNTs surfaces. EDX and ICP analysis shown about 11% Cu (II) and about 8.5% of N element in the catalyst structure. Also, other characterization data confirmed the successfully preparation of synthesized catalyst. The efficiency of this novel catalyst was evaluated through the green synthesis of two variety of spirooxindole derivatives in a One-pot multi component reaction in ethanol as a green solvent. The catalyst showed high efficiency in this process and all of spirooxindoles were obtained after short time (18 min) in high to excellent yields (89–95%). The structure of all obtained products was assigned with hydrogen and carbon nuclear magnetic resonance (1H and 13C NMR) and FTIR. Furthermore, the catalyst could be easily recovered and directly reused at least five times without a notable reduction in activity. The other advantages of the presented methodology are high yields of products without the formation of by-products, simple and clean process, mild reaction conditions and agreement with green chemistry protocols.

Nickel ferrite nanoparticles doped on hollow carbon microspheres as a novel reusable catalyst for synthesis of N-substituted pyrrole derivatives

Pyrroles are widely spread worldwide because of their critical applications, especially pharmacology. An expedition method for one-pot synthesis of N-substituted pyrrole derivatives has been presented by a reaction between 2,5-dimethoxytetrahydrofuran and various primary aromatic amines in the presence of NiFe2O4 anchored to modified carbon hollow microspheres (NiFe2O4@MCHMs) as a recoverable reactive catalyst. The Classon-Kass method has been used to synthesize the pyrroles in excellent yields and short reaction times in the same direction with green chemistry rules. This reaction was carried out by employing NiFe2O4@MCHMs as a catalyst to make a simple procedure with short activation energy in water as an accessible, non-toxic, and biodegradable solvent. This catalyst provides a promising pathway to synthesize N-substituted pyrroles several times in a row through the recyclability without remarkable loss of its catalytic activity. The NiFe2O4@MCHMs nanocatalyst was characterized by applying FT-IR, XRD, FE-SEM, TEM, EDS, BET, TGA, VSM, and elemental mapping techniques. Also, the synthesized N-substituted pyrrole derivatives were identified using melting point, FT-IR, and 1H NMR analyses.

Grafting Cu(II)-5-amino-1H-tetrazole complex on magnetic graphene oxide as an efficient magnetically recoverable catalyst for the synthesis of N-benzyl-N-aryl-5-amino-1H-tetrazoles

Grafting Cu(II)-5-amino-1H-tetrazole complex on magnetic graphene oxide as an efficient magnetically recoverable catalyst for the synthesis of N-benzyl-N-aryl-5-amino-1H-tetrazoles

Ce-Zr UiO-66 MOF as recyclable heterogeneous catalyst for selective N-methylation

Metal-organic frameworks (MOFs) are proven heterogeneous recoverable catalysts in a number of organic transformations. However, their role in the reaction of amines with dialkyl carbonates has only been partially investigated. In this paper, the catalytic potential of Ce-Zr UiO-66 MOF towards the N-alkylation of secondary amines with dimethyl carbonate has been investigated. The desired MOF catalyst was prepared by the solvothermal method and its morphology, texture, porosity, functionality, and crystallinity were examined before its catalytic investigation. The MOF consisted of sphere-like particles with a surface area of 272 m2/g and an average pore size of 3.4 nm. Under the optimized conditions, the aromatic and heterocyclic amines yielded the N-methylated derivatives as the sole or the major product in the presence of Ce-Zr UiO-66 MOF. The maximum methylation percentage achieved was 100%. The reaction followed the pseudo-first-order rate kinetics and the heterogeneous bimetallic Ce-Zr UiO-66 MOF was reused four times without any significant activity loss. Thus, the Ce-Zr UiO-66 MOF serves as an efficient, selective, and reusable heterogeneous catalyst in N-methylation reactions.

Microwave-assisted synthesis of -CF3 functionalized 3,4-dihydropyrimidinone/thione/imine derivatives by using potassium phthalimide (PPI) as a green and reusable organocatalyst and their anti-microbial evaluation

One-pot synthesis of novel -CF3 functional group containing 3,4-dihydropyrimidinone/thione/imine derivatives 8a-l, 9a-l and 10a-l has been successfully performed in high yields through the reaction of aromatic aldehydes, β-dicarbonyl compound, urea/thiourea/guanidine hydrochloride by using potassium phthalimide (PPI) as organocatalyst under solvent-free conditions under microwave irradiation at 300 W. PPI has been introduced as an efficient and biodegradable organocatalyst in Biginelli condensation with excellent reusability. The good yield of products, fast reaction time, simple work-up procedure, as well as usage of nontoxic, reusable, and easily recoverable catalyst under magnetic starring have been counted as advantages of the applied process. This organocatalyst can be removed after completion of reaction and reused several times under the same reaction conditions without significant loss of catalyst activity. The anti-microbial activity of all newly synthesised Biginelli products has been investigated against a variety of microorganisms such as E. coli, S. aureus, S. pyogenes, P. aeruginosa, C. albicans, A. niger and A. clavatus.

Iodine supported poly(4-vinylpyridine): Efficient and recoverable catalyst for the synthesis of 3,3-diheteroaromatic oxindoles

An efficient methodology for the synthesis of 3,3-diheteroaromatic oxindole derivatives has been demonstrated by coupling indole-2,3-dione (isatin) with differently substituted indoles and pyrrole in the presence of iodine-supported on poly(4-vinylpyridine) under neutral and solvent-free conditions. The products were obtained in a short time and good to excellent yields.

MIL-53(Fe) derived magnetic CuFe2O4/Fe2O3 composite for catalytic oxidation of sulfamethoxazole via peroxymonsulfate activation

Design of metal–organic framework (MOF) derived metal oxides is an effective approach for environmental remediation. The current study describes the fabrication of MIL-53-derived perforated CuFe2O4/Fe2O3 using a facile, one-step, post-thermal solid-state approach by varying Cu/Fe ratios. Herein, the release of CO2 and H2O during the thermal treatment facilitates the incorporation of Cu2+ onto the Fe2O3 structure, forming a perforated hollow CuFe2O4/Fe2O3 composite via an in-situ ion-exchange mechanism. The optimised catalyst CF-0.5 displays a high degradation efficiency for the removal of sulfamethoxazole (SMX) by heterogeneous activation of peroxymonsulfate (PMS), ascribing to the better textural, morphological, and elemental properties of the novel catalyst. Important reaction parameters such as pH, catalyst loading, PMS dosage, pollutant kind and concentration, and reaction temperature are further optimised to develop a cost-effective catalytic system. The magnetically recoverable catalyst outlines a high stability rate, and only a 9 % efficiency loss is observed even after the fourth cycle. Reactive oxygen species (ROS) are identified by electron paramagnetic resonance spectroscopy (EPR) and their roles are determined by performing quenching experiments. In the end, a detailed study of the mineralisation ability and reaction intermediates is performed and possible pathways for the degradation mechanism are proposed. This study not only introduces a facile approach for the fabrication of MOF-driven nanomaterials but provides insights into the removal of emerging contaminants such as SMX.

Pd NPs encapsulated by COF in nitrogen-doped macroporous chitosan carbon microspheres act as an efficient and recyclable multifunctional catalyst

Developing efficient, recoverable, and versatile palladium catalysts is of great significance. In this paper, nitrogen-doped macroporous chitosan carbon microspheres (MCM) were prepared by emulsion polymerization method with polystyrene microspheres as a template. The core-shell structured MCM@Pd@COF catalysts were then prepared using a coral-structured COF shell layer to seal the Pd NPs in the channels of the MCM. The introduction of COF with good photocatalytic properties improved the stability of the material while imparting its photocatalytic properties without affecting its catalytic activity. MCM@Pd@COF efficiently catalyzed the Suzuki coupling reaction (Iodobenzene and phenylboronic acid, 98 % yield, TON = 6.7 × 105, TOF = 3.4 × 105 h−1), and the reduction of 4-nitrophenol (4-NP, reaction rate constant Kapp = 9.48 × 10−1 min−1). The kinetic study revealed that the reduction reaction of 4-NP by MCM@Pd@COF was compliant with the quasi-first-order kinetic model. Furthermore, MCM@Pd@COF removed up to 96.3 % of high concentrations of rhodamine B (RhB) within 30 min under visible light irradiation. Mechanistic investigation showed that MCM@Pd@COF efficiently promotes the production of O2– and OH radicals under visible light irradiation, which drives the photocatalytic degradation of organic dyes. There was no significant decrease in the catalytic activity of MCM@Pd@COF over the eight uses.

Cobalt-doped ZnAl-LDH nanosheet arrays as recyclable piezo-catalysts for effective activation of peroxymonosulfate to degrade norfloxacin: non-radical pathways and theoretical calculation studies

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) are considered promising technologies for the degradation of recalcitrant norfloxacin in wastewater. However, this technology exhibits sluggish carrier transport and slow regeneration of the catalytic center. In this study, cobalt-doped ZnAl-layered double hydroxides (ZnAl-LDH) were synthesized as recoverable piezoelectric catalysts for efficient activation of PMS. The cobalt-doped ZnAl-LDH (0.06 mmol cobalt) demonstrated the most effective degradation performance within 15 min, achieving a degradation efficiency of 91.50% and a rate constant of 0.1644 min−1. The constructed piezoelectric catalytic system was mainly based on a non-radical mechanism, including singlet oxygen (1O2) and electron transport. Notably, the remarkable piezoelectric properties of the catalyst accelerated carrier transport and promoted regeneration of the catalytic active center (Co2+). The remarkable structural stability of the catalyst not only resulted in a significant reduction of Co leaching, but also enabled its successful adaptation to complex aqueous environments. This study provides non-negligible importance for future research on the structure and mechanism of piezoelectric catalysts used for PMS activation.

Catalytic activity of Mn(III) porphyrin complex supported onto cross linked polymers in the green oxidation of malathion with hydrogen peroxide in aqueous solution

Developing effective, affordable, and recoverable heterogeneous catalysts is one of the foremost challenges in modern chemistry. Mn(III) complexes of 5-(4-aminophenyl) −10, 15, and 20-triphenyl porphyrin 1 immobilized covalently on polymethyl methacrylate (PMMA) 2 and poly(methyl methacrylate –co- styrene) (PMMA/ST) 3 were synthesized, characterized, and applied for degradation of malathion with H2O2 in aqueous solution. Mn(III) porphyrin complex anchored on cross linked polymers 4 and 5 show high catalytic activity for malathion (pesticide) degradation in an aqueous solution with green oxidant H2O2. The catalytic efficacy of malathion degradation was highest with the Mn(III) porphyrin complex covalently anchored on (polymethyl methacrylate-co-styrene) 5. The optimum conditions, including the effect of pH, catalyst concentration, and H2O2 concentration on the degradation of malathion, were investigated. The reuse and stability of catalysts were examined, and the findings proposed that the Mn(III) porphyrin complex 5 has no noticeable changes in the removal efficiency up to five consecutive cycles. GC–MS analyses showed that the degraded compounds and intermediates formed from malathion degradation were non-toxic to E. coli bacteria. For the degradation of dissolved malathion pesticides in an aqueous solution, the use of Mn(III) porphyrin complex 5 in the presence of H2O2 has the potential to be advantageous.

Solid waste-supported nickel nanoparticles: A sustainable, recoverable, and efficient heterogeneous catalyst for organic pollutant degradation

The processing of polymeric solid wastes into industrial processes is of outmost importance from an environmental and economic point of view. Herein, a simple and straightforward route was developed for immobilizing nickel nanoparticles on the surface of waste loose fill as a recoverable heterogeneous catalyst. The nickel nanoparticles exhibited a spherical-like shape and were not uniformly dispersed in the loose fill matrix. The carbonyl and/or carboxyl groups would initiate active sites along the loose fill chains, which serve as adsorption centers and tight fixing of nickel ions. The catalytic activity of nickel@loose fill nanocomposite was evaluated through the degradation of 4-nitrophenol, reactive blue dye, and mixture of both. The results indicated the catalyst retained 87% of its activity after 20 cycles. The use of a solid waste as a supporting matrix in heterogeneous catalysis may reduce the fabrication cost and improve the contact between the reactants and Ni nanoparticles due to the porosity of loose fill. The use of waste material made from renewable resources (vegetable starch) could explore genuinely and sustainable materials as alternatives to the traditional polymers in heterogeneous catalysis.

Single Atom and Metal Cluster Catalysts in Organic Reactions: From the Solvent to the Solid

AbstractThe supporting of pre‐formed soluble metal catalysts on solids is a typical methodology to transform soluble but unrecoverable metal complexes into recoverable and reusable solid catalysts. However, this methodology has been barely implemented for ligand‐less, bare single metal atoms (SMAs) and nanoclusters (NCs) in organic synthesis, despite these ultrasmall species can be formed in‐situ during reaction and be the truly catalytic species. The aim of this review is to explore how to speciate active single metal atoms and clusters during homogeneous catalysis (in solution), without ligands, and to prepare them independently, to be transferred to solid supports and catalyze organic reactions. In many cases, the translation to solids gives single atom catalysts (SACs). Supporting of ultrasmall metal aggregates gives more stable, reusable and, sometimes, chemoselective catalysts for representative organic reactions.

Design and synthesis of Ni3ZnC0.7 catalyst derived from a bimetallic Ni/Zn metal-organic frameworks for efficient synthesis of 2-arylbenzimidazole

Developing efficient bimetallic Ni/Zn metal organic frameworks (MOFs) derived Ni3ZnC0.7 alloy catalyst for cyclization reactions is highly anticipated. Bimetallic Ni/Zn-PTA MOFs with flower-like microspheres morphology was synthesized by using a facile hydrothermal method and used as a precursor for preparation of the catalyst. Then, a ZnO supported Ni-Ni3ZnC0.7 incorporated carbon catalyst (Ni-Ni3ZnC0.7/ZnO-C) was obtained by deriving from the Ni/Zn-PTA MOFs through one-step pyrolysis. The developed Ni-Ni3ZnC0.7/ZnO-C catalyst was used as a recoverable heterogeneous catalyst for synthesis of 2-arylbenzimidazoles by cyclization reaction of phenylmethanamines and 2-nitroanilines in good yields. Various characterizations (e.g. SEM/EDX, XRD, TEM, FT-IR, XPS and Raman) revealed that the catalyst exhibited good performance for cyclization reaction, which are ascribed to particular hierarchical structure, as well as synergistic effect between Ni and Ni3ZnC0.7. As a result, the Ni-Ni3ZnC0.7/ZnO-C catalyst showed excellent stability and activity for the condensation cyclization reaction. This bimetallic MOFs-derived Ni-Ni3ZnC0.7 catalyst opens up a potential way for fabricating other Carbon supported alloy catalysts in heterogeneous catalysis reactions.

Synthesis of chiral salen-MnIII complexes tagged with ionic liquid as recoverable homogeneous catalysts for the oxidative kinetic resolution of (±)-secondary alcohols

New chiral salen ligands tagged with imidazolium based ionic liquids (ILs) were synthesized from the 5-bromopentyl benzoate functionality at C-5 position of salicylaldehyde moiety, N-methylimidazole, and (1R,2R)-1,2-diphenylethane-1,2-diamine/(1R,2R)-cyclohexane-1,2-diamine in 81–92% yields. The chiral salen ligands were further reacted with Mn(OAc)2.4H2O in dry methanol under N2 atmosphere, followed by air oxidation with LiCl to produce the IL tagged chiral salen-MnIII complexes 1(a–c) and 2(a–c) in 79-86% yields. The catalytic activities of these complexes were evaluated in the oxidative kinetic resolution of (±)-1-phenylethanol (8a) with N-bromosuccinimide (NBS) as an oxidizer in biphasic solvent system [H2O - organic solvent (2: 1, v/v)] at 0 °C. The enantioselective oxidation of various (±)-secondary alcohols catalyzed by complex 1c (1 mol%) afforded the chiral secondary alcohols with up to 99% enantiomeric excess and 29.6 krel (selectivity factor) value. The IL tagged chiral salen-MnIII complex 1c was easily recovered with hexane and subsequently reused for five recycles with no significant loss in conversion of (±)-1-phenylethanol (8a) and ee of the resolved product.

Recyclable copper-decorated magnetic composites as non-precious catalysts for effective removal of 4-nitrophenol and azo dyes

Carbonized lotus leaf (CLL) from agricultural waste is employed as the support to prepare the novel Cu-Fe3O4/carbonized lotus leaf (CuX-FCLL) catalysts. The magnetic catalyst Cu1.5-FCLL demonstrated desirable catalytic activity for the reduction of organic dyes (Congo red, Methyl orange) and nitroaromatic compounds (3- and 4-nitrophenols). The magnetically recoverable catalyst (Cu1.5-FCLL) exhibited ultrafast catalytic activity for 4-nitrophenol reduction with a conversion rate of over 98% within 30 s, which was comparable to those noble metal catalysts widely used. The CLL with unique papillae structures could provide large surface areas and prevent aggregation of metal NPs, and boost the catalytic performance of Cu1.5-FCLL by a synergetic effect. Such a magnetic catalyst was facilely recovered and reused after ten cycles with negligible loss of catalytic performance. This work presents an efficient green catalyst to replace noble metals for wastewater treatment.