Recoverable Heterogeneous Catalyst Research Articles

One-pot synthesis of chromenes in the presence of magnetic nanocomposite based on NH2-UiO-66(Zr), graphene oxide and Fe3O4

In this research, GO/Fe3O4/UiO‑66-NH2, a new magnetically recoverable heterogeneous catalyst, was prepared and characterized using various spectroscopic techniques and elemental analysis methods. The promoting ability of GO/Fe3O4/UiO‑66-NH2 was studied in the synthesis of chromenes via one-pot three-component condensation of 4‐hydroxycoumarin, 2‐hydroxynaphthalene‐1,4‐dione and aromatic aldehydes at 110 °C under solvent-free conditions. This new protocol is included some important features such as lower loading of the catalyst, excellent yields (88%–98%), short reaction times (5–10 min), easy work-up procedure, and easy recovery using a simple magnet. The catalyst was characterized by SEM, XRD, EDX, BET, TGA and FT-IR analysis.

Biomimetic Oxidation of Sulfides Catalyzed by Polystyrene-Bound Dioxomolybdenum Complex as an Efficient Recoverable Heterogeneous Catalyst

Biomimetic Oxidation of Sulfides Catalyzed by Polystyrene-Bound Dioxomolybdenum Complex as an Efficient Recoverable Heterogeneous Catalyst

Selective oxidation of benzylic alcohols using Mo(VI) Schiff base complex supported on magnetic nanoparticles as a new recoverable heterogeneous catalyst

Selective oxidation of benzylic alcohols using Mo(VI) Schiff base complex supported on magnetic nanoparticles as a new recoverable heterogeneous catalyst

Fe3O4@C@PrS-SO3H: A Novel Efficient Magnetically Recoverable Heterogeneous Catalyst in the Ultrasound-Assisted Synthesis of Coumarin Derivatives

A novel magnetic core-shell nano-particles of Fe3O4@C@PrS-SO3H were generated and utilized in the green synthesis of coumarin derivatives under conventional and ultrasound-assisted conditions. The synthesized nano-catalysts were fabricated through a three-step method, including the synthesis of Fe3O4@C nano-particles, then coated by (trimethoxysilyl)-1-propanethiol, finally modified with chlorosulfonic acid. The nano-catalysts were identified using FT-IR, X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA) techniques. The catalyst efficiency of the synthesized Fe3O4@C@PrS-SO3H NPs was scrutinized in the Pechmann condensation of phenol and β-ketoester derivatives under solvent-free conditions. The synthesized catalyst was evaluated as very effective under conventional and ultrasonic assistant reaction conditions. A significant reusable activity was observed for the catalyst.

Photocatalytic activation of peroxydisulfate by magnetic Fe3O4@SiO2@TiO2/rGO core–shell towards degradation and mineralization of metronidazole

In the present work, the degradation of metronidazole (MNZ) antibiotic by photocatalytic activation of peroxydisulfate (PDS) was studied in a batch environment. In this regard, TiO2 nanoparticles (NPs) with magnetic core–shell structure were anchored on the reduced graphene oxide (rGO) to fabricate the Fe3O4/SiO2/TiO2@rGO nanocomposite (FST@rGO) and applied as a recoverable heterogeneous catalyst along with ultraviolet (UV) light for activation of PDS. The nanocomposite was synthesized successfully by the sol–gel method and then characterized by using FESEM, EDS, XRD, Raman, EIS, BET, TEM, VSM, PL, and UV–VIS techniques. The degradation rate of MNZ was evaluated as a function of different concentrations of catalyst, PDS, and MNZ as well as the solution pH to determine the optimum operational conditions. Photocatalytic activity of TiO2 toward the degradation of MNZ was enhanced significantly after its magnetization by core–shell structure. Activated PDS exhibited excellent performance for degradation of MNZ in the wide range of pH. Under optimum conditions (pH:7, PDS:3 mM and FST@rGO:0.1 g L-1), >94% of MNZ and 58% of total organic carbon (TOC) were removed within 60 min. Based on trapping tests, HO•, 1O2, holes, and SO4•− species were identified as major reactive species during the MNZ degradation process. After four cycles of reuse the FST@rGO was able to remove 63.5% of MNZ, revealing relative reusability potential of the nanocomposite. In summary, integration of UV light and FST@rGO toward the activation of PDS could be introduced as a promising technique for application in environmental objectives, due to the good performance in the degradation/mineralization, easily separation, and high reusability potential of catalyst.

One-pot synthesis of 1-(benzothiazolylamino)aryl methyl-2-naphthols and 3-benzothiazolyl 2,3-dihydroquinazolinones using a magnetically recoverable core–shell nanocomposite as catalyst

Abstract Nano-magnetite-supported sulfated polyethylene glycol (Fe3O4@PEG-SO3H) was prepared, characterized and utilized as a magnetically recoverable heterogeneous catalyst for the one-pot, three-component reaction of 2-aminobenzothiazole, aldehydes and 2-naphthol/isatoic anhydride resulting in efficient formation of 1-(benzothiazolylamino)arylmethyl-2-naphthol or dihydroquinazolinones derivatives. The significant features of this method include green conditions, operational simplicity, minimizing production of chemical waste, shorter reaction times and good to high yields. In addition, the nanocatalyst can easily be separated from the reaction mixture by application of a magnetic field and reused without significant deterioration in its catalytic activity.

Bovine serum albumin‐silica functionalized γ‐Fe2O3 nanoparticles (BSA‐Si@Fe2O3): A highly efficient and magnetically recoverable heterogeneous catalyst for the synthesis of substituted pyrrole derivatives

The present study used silica functionalized bovine serum albumin as a bio‐support for γ‐Fe2O3 nanoparticles (NPs) to synthesize a magnetically recoverable heterogeneous catalyst (BSA‐Si@Fe2O3). The structure of the catalyst was well established by various techniques such as Fourier transform infrared (FT‐IR) spectroscopy, Scanning Electron Microscope/Energy Dispersive X‐ray (SEM/EDX), elemental mapping, Transmission Electron Microscope (TEM), Thermogravimetric (TG), Powder X‐ray diffraction (XRD), X‐ray Photoelectron Spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and Electron Paramagnetic Resonance (EPR) analyses. The catalyst also possesses magnetic properties as shown by Vibrating Sample Magnetometer (VSM). The strong acidic properties of the catalyst was calculated using potentiometric titration showing Ei value in the range of 0 < Ei < 100 mV. The catalyst was found to be highly efficient for the synthesis of pyrroles affording high yield (87%–94%) in short reaction time period under environmentally feasible reaction conditions (high atom economy and low E‐factor). The BSA‐Si@Fe2O3 could be recycled up to six cycles with insignificant loss in catalytic potential.

FeS₂ Loaded Porous SiO₂ Ball as a Tweezers Recoverable Heterogeneous Fenton Catalyst with Enhanced Recyclability.

We report a novel FeS₂ loaded large SiO₂ sphere (diameter of 3 cm) via double immobilization with (3-mercaptopropyl)trimethoxysilane (KH590) as a highly efficient, stable, and tweezers-recoverable heterogeneous Fenton-like catalyst (FeS₂/KH590/SiO₂@KH590). Notably, as-prepared composite catalyst exhibits a significant recycling improvement (10 runs) over free FeS₂ powder (3 runs). The outstanding recyclability and stability of FeS₂/KH590/SiO₂@KH590 can be attributed to the passivation of FeS₂ nanoparticles on SiO₂ surface by KH590 and subsequent prevention of Fe2+ leaching. Overall, our work provides a new avenue towards fabricating composite Fenton-like catalyst with high stability, enhanced recyclability and the advantage of easy separation.

Metal(II) Coordination Polymers from Tetracarboxylate Linkers: Synthesis, Structures, and Catalytic Cyanosilylation of Benzaldehydes

Three 2D coordination polymers, [Cu2(µ4-dpa)(bipy)2(H2O)]n∙6nH2O (1), [Mn2(µ6-dpa)(bipy)2]n (2), and [Zn2(µ4-dpa)(bipy)2(H2O)2]n·2nH2O (3), were prepared by a hydrothermal method using metal(II) chloride salts, 3-(2′,4′-dicarboxylphenoxy)phthalic acid (H4dpa) as a linker, as well as 2,2′-bipyridine (bipy) as a crystallization mediator. Compounds 1–3 were obtained as crystalline solids and fully characterized. The structures of 1–3 were established by single-crystal X-ray diffraction, revealing 2D metal-organic networks of sql, 3,6L66, and hcb topological types. Thermal stability and catalytic behavior of 1–3 were also studied. In particular, zinc(II) coordination polymer 3 functions as a highly active and recoverable heterogeneous catalyst in the mild cyanosilylation of benzaldehydes with trimethylsilyl cyanide to give cyanohydrin derivatives. The influence of various parameters was investigated, including a time of reaction, a loading of catalyst and its recycling, an effect of solvent type, and a substrate scope. As a result, up to 93% product yields were attained in a catalyst recoverable and reusable system when exploring 4-nitrobenzaldehyde as a model substrate. This study contributes to widening the types of multifunctional polycarboxylic acid linkers for the design of novel coordination polymers with notable applications in heterogeneous catalysis.

Aerobic Cu and amine free Sonogashira and Stille couplings of aryl bromides/chlorides with a magnetically recoverable Fe3O4@SiO2 immobilized Pd(II)-thioether containing NHC

Two value added CC cross coupling reactions; Sonogashira and Stille couplings were achieved at milder conditions in the catalytic presence of a magnetically recoverable heterogeneous catalyst Fe3O4@SiO2@NHC^SPh-Pd(II). The catalyst was earlier reported for Suzuki-Miyaura reaction, and as an extension of its catalytic efficiency, the Stille and Sonogashira cross coupling reactions under aerobic condition has been explored in present report. The Sonogashira coupling of aryl bromides and terminal alkynes produced an excellent yield (~96% at 0.25 mol% Pd) of the desired coupling product under copper and amines free conditions. Moreover, an excellent Stille coupling of readily available and more latent aryl chlorides and trialkylstannane was obtained (yields up to 95% at 0.25 mol% Pd) in absence of toxic fluorides additives. The broad substrate scope of the catalyst for both the coupling reactions and the magnetically recoverable feature of catalyst make this reaction highly desirable for industrial applications of present heterogeneous catalysis.

Gold nanoparticles decorated biguanidine modified mesoporous silica KIT-5 as recoverable heterogeneous catalyst for the reductive degradation of environmental contaminants

This current study involves the novel synthesis of Au nanoparticles (Au NPs) decorated biguanidine modified mesoporous silica KIT-5 following post-functionalization approach. The tiny Au NPs were being stabilized over the in situ prepared biguanidine ligand. The high surface area material was characterized using analytical techniques like Fourier Transformed infrared (FT-IR) spectroscopy, N2-adsorption–desorption isotherm, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction study (XRD). Our material was found to be an efficient catalyst in the reductive degradation of harmful water contaminating organic dyes like Methylene blue (MB), Methyl Orange (MO) and Rhodamin B (RhB) in presence of NaBH4 at room temperature. The whole procedure was followed up with the help of time dependant UV–Vis spectroscopy. All the reactions followed pseudo-unimolecular kinetics and corresponding rate constant were determined. The reduction rate becomes high in presence of higher load of catalysts.

Facile preparation of nanostructured Pd-Sch-δ-FeOOH particles: A highly effective and easily retrievable catalyst for aryl halide cyanation and p-nitrophenol reduction

Iron based compounds are good candidates as supports to immobilize different transition metals due to their eco-friendly nature, capability of facilitating chemical modifications, inexpensiveness, high stability and easy recoverability. In this study, palladium nanoparticles (Pd NPs) were successfully stabilized on designed Schiff base modified δ-FeOOH particles as a highly effective and readily recoverable heterogeneous catalyst (Pd-Sch-δ-FeOOH nanocatalyst). The catalyst was fabricated via a facile multi-step approach without utilizing any additional reducing agents. The Pd-Sch-δ-FeOOH was characterized by Fourier transforms infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET). Characterization studies confirmed that the prepared small sized Pd NPs were spherically shaped and well dispersed on the surface of Schiff base modified δ-FeOOH. The catalytic efficiency of Pd-Sch-δ-FeOOH nanocatalyst was then tested in the preparation of benzonitriles through cyanation of aryl halides using K4[Fe(CN)6] has been utilized as a cyanation agent and also reduction of p-nitrophenol (p-NP) using NaBH4 as the reducing agent. Benzonitriles were characterized using GC-MS. Catalytic studies showed that benzonitriles were obtained in good reaction yields in the presence of heterogeneous Pd-Sch-δ-FeOOH nanocatalyst (87–98%). It was found that Pd-Sch-δ-FeOOH was also a useful nanocatalyst for p-NP reduction at ambient temperature in eco-friendly media within 2 min. The reduction rate for p-NP with Pd-Sch-δ-FeOOH was measured via UV–Vis spectroscopy from 250 nm to 550 nm. Furthermore, Pd-Sch-δ-FeOOH nanocatalyst was able to remain active for six successive runs due to its recyclable/reusable nature.

A Brønsted acidic ionic liquid anchored to magnetite nanoparticles as a novel recoverable heterogeneous catalyst for the Biginelli reaction.

In this study, simple and effective methods were used for the preparation of an ionic liquid that immobilized magnetite nanoparticles. Fe3O4 nanoparticles were prepared via a chemical co-precipitation method. Then, a SiO2 shell was coated on the magnetic core via the Stober method. Finally, CPTES (chloropropyltriethoxysilane) and morpholine were coated on the SiO2 shell. Morpholine sulfate, an acidic ionic liquid, was successfully bound to magnetite nanoparticles (Mag@Morph-AIL) and this was used as an efficient catalyst for the preparation of 3,4-dihydropyrimidinones. Compared to previous works, the easy separation of the nanocatalyst using an external magnet and the recyclability, non-toxicity, versatility, and high stability of the catalyst, combined with low reaction times and excellent yields, make the present protocol very useful for the synthesis of the title products. The synthesized products and catalyst were confirmed via1H-NMR, 13C-NMR, FT-IR, scanning electron microscope, X-ray diffraction, and elemental analysis.

Zr@IL-Fe3O4 MNPs as an efficient and green heterogeneous magnetic nanocatalyst for the one-pot three-component synthesis of highly substituted pyran derivatives under solvent-free conditions.

The present study was conducted to synthesize Zr@IL-Fe3O4 MNPs as a new magnetically recoverable heterogeneous catalyst, which was then characterized by Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The catalytic behavior of the Zr@IL-Fe3O4 MNPs was efficiently used for the synthesis of highly substituted pyran derivatives via a one-pot three-component condensation of 4-hydroxycoumarin/dimedone, malononitrile, and arylaldehydes under solvent-free conditions. This new methodology demonstrated some important features, including short reaction times, excellent yields, lower loading of the catalyst, easy work-up, and recyclability of the catalyst for a minimum of six times without any noticeable decrease in catalytic activity.

Oxidative Desulfurization and Denitrogenation of Simulated Fuels Catalyzed by TBAPMo11Cu@CuO as a High-Performance and Recoverable Heterogeneous Phase-Transfer Catalyst

Aimed at catalytic oxidative desulfurization (cat-ODS) of sulfur-containing aromatic compounds (SAs) and catalytic oxidative denitrogenation (cat-ODN) of nitrogen-containing aromatic components (NAs) to control air pollution, we successfully designed and synthesized a new green catalyst (named as TBAPMo₁₁Cu@CuO) based on quaternary ammonium salt of copperᴵᴵ-monosubstituted phosphomolybdate [(n-C₄H₉)₄N][PMo₁₁CuO₃₉] (TBAPMo₁₁Cu) and copper oxide (CuO) via a sol–gel method. Cat-ODS and cat-ODN processes of SAs (thiophene (Th) and dibenzothiophene (DBT)), NAs (pyridine (Py) and carbazole (CBZ)) were carried out using hydrogen peroxide green oxidant and poly(ethylene glycol) (PEG-200), which is considered as a green extractant over a TBAPMo₁₁Cu@CuO catalyst. This new catalyst demonstrated a superb catalytic activity in the oxidation of SAs and NAs and long-term stability for producing ultraclean fuels: 97, 98, 99, and 98% values of conversion were obtained for Th, DBT, Py, and CBZ, respectively, at 35 °C. The results proved that Th and DBT were converted to the corresponding sulfoxides and sulfones, while Py and CBZ were oxidized to the corresponding N-oxides. Accordingly, the oxidized product of CBZ was identified as carbazole-9-carbaldehyde. Also, the removal of a considerable amount of Th, DBT, Py, and CBZ is possible via catalytic oxidation–extraction; however, simple solvent extraction (using methanol, ethanol, and acetonitrile) was inadequate for deep denitrogenation and desulfurization. TBAPMo₁₁Cu@CuO as a catalyst indicated excellent reusability for five oxidation cycles. The high performance of TBAPMo₁₁Cu@CuO/H₂O₂/PEG-200 can prove it as a promising green method for fuel purification.

Erratum: A green and chemoselective synthesis of coumarins via Pechmann condensation using recoverable heterogeneous catalyst (Au@pSiO2)

Erratum: A green and chemoselective synthesis of coumarins via Pechmann condensation using recoverable heterogeneous catalyst (Au@pSiO2)

Design and Synthesis of Supramolecular Polymer Network Equipped with Pd-porphyrin: An Efficient and Recoverable Heterogeneous Catalyst for C–C Coupling Reactions

The present study aimed to explain a modern and attractive protocol for synthesizing hypercross-linked conjugated supramolecular polymer network contains palladium(II) porphyrin based on calix[4]resorcinarene as an efficient heterogeneous catalyst. Thus, characterizations were conducted by using spectroscopic methods including powder X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy, FT-IR, and UV–Vis spectroscopy. In addition, catalytic activity of Pd-porphyrin@polymer was evaluated for C–C coupling reactions. The catalyst demonstrated an excellent activity, which is highly potential for forming new bond under mild conditions. The synthesis of a novel, green and recoverable heterogeneous catalyst by grafting Pd-porphyrin on the surface of polymeric calix[4]resorcinarene for the synthesis of C–C coupling reactions.

Recyclable copper catalyst on chitosan for facile preparation of alkyl/aryl mixed phosphates via deaminated esterification between diphenylphosphoryl azides and aliphatic alcohols

An efficient methodology was established for the preparation of alkyl/aryl mixed phosphates under aerobic conditions promoted by a easily recoverable heterogeneous catalyst. This highly active copper catalyst was obtained by directly mixing of copper precursor with chitosan solution, followed by a simple work-up process. In this catalytic system, different phosphoryl azides and aliphatic alcohols were employed to generate desired products in moderate to excellent yields with good functional group tolerance. This protocol provided a practical application of the chitosan supported heterogeneous copper catalyst towards a novel PO bond formation.

Copper(II)-Ethanolamine Triazine Complex on Chitosan-Functionalized Nanomaghemite for Catalytic Aerobic Oxidation of Benzylic Alcohols

In this study a novel, effective and recoverable Cu(II)-catalyst was synthesized by incorporating of Cu(OAc)2 within ethanolamine-triazine derivative (TAETA) attached to chitosan (Chs)-functionalized γ-Fe2O3 nanoparticles [MNP@Chs/TAETA-Cu(II)]. It was characterized by different techniques such as FT-IR, EDS, ICP, TEM, TGA and VSM. The as-prepared nanocomposite demonstrated high oxidation activity and desired selectivity in the aerobic oxidation of structurally diverse set of benzyl alcohols. Spectral results and leaching experiments revealed that this magnetically recoverable heterogeneous catalyst preserved its structure after it was reused several times. This protocol offers some beneficial features such as the use of oxygen as an ideal oxidant, stability of nanocomplex, easily catalyst separation by using an external magnetic field and efficient recycling as well as the lack of by-products.

A green and chemoselective synthesis of coumarins via Pechmann condensation using recoverable heterogeneous catalyst (Au@pSiO2)

Nano Au@porous SiO2 as a heterogeneous catalyst was prepared and characterized by Fourier transform infrared, X‐ray powder diffraction, transmission electron microscopy, thermogravimetric analysis and inductively coupled plasma–atomic emission spectroscopy techniques and then used as an efficient catalyst in the condensation of various phenols with ethyl acetoacetate for the preparation of coumarin derivatives through the Pechmann reaction. The combined merits of chemoselective and solvent free reaction conditions and the recyclability of the nanostructured catalyst make the condensation a safe operation, with low pollution, rapid access to products and simple workup.