Recyclable Heterogeneous Catalyst Research Articles

Paracetamol degradation by photo-assisted activation of peroxymonosulfate over ZnxNi1−xFe2O4@BiOBr heterojunctions

Developing efficient and recyclable heterogeneous catalysts in advanced oxidation processes towards aqueous organic pollutants degradation on real samples remains challenging. Herein, semiconductor heterojunction photocatalysts with variable composition (ZnxNi1−xFe2O4@BiOBr; x = 0, 0.2, 0.5, 0.8 and 1) were synthesized through a two steps hydrothermal process. The influence of cation composition, microstructure heterojunction, catalyst and peroxymonosulfate (PMS) dosage and pH variation were investigated for the degradation of paracetamol (PAM) as target pollutant. Real degradation datasets from commercial tablet solutions were compared with pure paracetamol (p-PAM). Doping Ni into ZnFe2O4 significantly affect the catalytic performance as well as enable magnetic removal of catalyst. The ratio between ZnxNi1−xFe2O4 and BiOBr was also optimized to realize best catalytic degradation. Complete removal of PAM was achieved after 100 min at optima conditions (0.5 g/L Zn0.8Ni0.2Fe2O4@BiOBr, 2 mM PMS, 10 mg/L PAM, UV-A, pH 7) while 64% removal account in 100 min in darkness. A chemical method probe, through free radical scavengers, revealed that SO4•- is the main specie involved in the degradation reaction. A novel degradation mechanism was proposed by the identification of eight different intermediates. Reusability of the heterojunction photocatalysts was studied after five consecutive treatments. Zn0.8Ni0.2Fe2O4@BiOBr efficiently activate PMS under UV-A irradiation vanishing PAM, one contaminants of most emerging concern found in water. This study will shed light into the understanding of photo-assisted PMS activation for aqueous pollution abatement.

Magnetically separable and efficient platinum catalyst: Amino ligand enhanced loading and Fe2+ facilitated Pt0 formation

AbstractUnderstanding the interaction between metal and the support is crucial in searching of efficient and recyclable noble metal heterogeneous catalysts. Herein, we report a core‐shell structured support for Pt catalyst with a magnetic Fe3O4 core and a porous silica shell bearing amino groups. The prepared catalyst Fe3O4@mSiO2‐APTES‐Pt showed a high loading of Pt (7.93 wt%) as well as a high fraction of active Pt0 species, which both contributed to the high activity toward a model hydrosilylation reaction between 1‐octene and 1, 1, 1, 3, 5, 5, 5‐heptamethyltrisiloxane (HMTS). X‐ray photoelectron spectra (XPS) analysis revealed that the amino ligands played a dominant role in Pt loading and Fe2+ probably facilitated the formation of low valence Pt0. Under the combined effect of magnetic nature of the support and proper support‐metal interactions, the catalyst exhibited excellent recyclability with a recovery of 99.7% and a yield of over 90% even after eight runs of recycling. This catalyst may provide a new option in designing and preparing heterogeneous catalysts that are highly recoverable, reusable, and recyclable.

Synthesis of α-amino phosphonates catalyzed by copper-based metal organic frameworks

In this paper we report a novel and straightforward method for the synthesis of α-amino phosphonates via three-component reaction of amines, aldehydes, and triethyl phosphite in the presence of Cu2(BDC)2DABCO (Cu-MOF) as a recyclable heterogeneous catalyst. The chemical structures of the all synthesized compounds were confirmed by NMR, IR and CHN analysis.

Synthesis of 2-iminothiazolidin-4-ones using guanine functionalized SBA-16 as a solid base catalyst

The first example of a one-pot three-component tandem annulation approach is described for the synthesis of 2-iminothiazolidin-4-ones by the reaction of aromatic/aliphatic amines, aryl isothiocyanates, and ethyl bromoacetate, catalysed by guanine-functionalized SBA-16, [SBA-16@G], as an efficient and recyclable heterogeneous solid base catalyst. The methodology is simple and offers a broad-substrate scope under mild reaction conditions.

Silver nanoparticles supported on UiO-66 (Zr): As an efficient and recyclable heterogeneous catalyst and efficient adsorbent for removal of indigo carmine

As incorporating silver nanoparticles (Ag NPs) into zirconium metal-organic frameworks (UiO-66) offer an extensive potential in numerous applications such as wastewater treatment and catalysis, we herein synthesized UiO-66, followed by incorporating different contents of Ag NPs into UiO-66. The prepared UiO-66 composites were identified by means of various techniques like X-ray-diffraction patterns (XRD), nitrogen adsorption desorption (BET), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) analysis. Besides, acidic properties of composites were examined using FTIR of chemisorbed pyridine and non-aqueous potentiometric titration. The results displayed that UiO-66 crystals exhibited sizes of 180 and 240 nm. Their surface area and total pore volume respectively reached 1593 m 2 g −1 and 0.834 m 3 g −1 , and decreased by incorporating Ag NPs to 863 m 2 g −1 and 0.432 m 3 g −1 at 5.0 wt% Ag/UiO-66. TGA data manifested that adding Ag NPs could improve the thermal stability of the primitive UiO-66. The as-synthesized composites were tested towards indigo carmine (IC) adsorption from aqueous media and in synthesis of 3,4-dihydro-pirimidin-2(1H)-ones (3,4-DHPs). The adsorption data showed that silver nanoparticles incorporation enhanced IC removal performance of UiO-66 and adsorption capacity was augmented from 87.2 mg g −1 (UiO-66) to 312.8 mg g −1 at 2.0 wt% Ag/UiO-66. This performance was efficient relying on adsorption isotherm measurements, indicating that incorporating Ag NPs augmented the number of adsorption sites and π–π interactions between adsorbate and adsorbent were enhanced, resulting in improved adsorption capacity towards anionic dyes. Also, incorporated Ag NPs show better catalytic activity in the preparation of DHPs and the yield reached 88% using 2.0 wt% Ag/UiO-66, imparting excellent recyclability for four cycles.

Synthesis of Functionalized-Magnetic Nanoparticles and Application as a Retrievable and Efficient Catalyst for the Green Synthesis of Pyrano[2,3-c]Phenazine-15-yl)Methanone Derivatives Under Solvent-Free Conditions

A novel method for the synthesis of four-component pyrano[2,3-c]phenazin-15-yl) methanone derivatives has been developed via condensation/Knoevenagel/Michael in the presence of Fe3O4@ZnO-SO3H as a recyclable heterogeneous catalyst under Solvent-Free Conditions, using microwave irradiation. This green process has many advantages such as high productivity, shorter reaction times, environmentally friendly, quick isolation, and prevention of hazardous solvents in the laboratory for the synthesis of pyrano[2,3-c]phenazin-15-yl)methanone derivatives, which are promising compounds in various aspects of medical sciences (pharmacy).

SYNTHESIS AND APPLICATION OF Cu-Fe HYDROTALCITE IN ALDOL REACTION

The heterogeneous recyclable catalyst, Cu-Fe hydrotalcite, was synthesized by coprecipitation, activated at 200oC and then successfully applied in Aldol reaction. The Aldol products were obtained in moderate yield under mild conditions, simple and environmentally benign process, with the recovery of hydrotalcite catalyst up to 99%. This procedure also exhibited efficiency in the total synthesis of Abhexone, a flavor with high demand in the food and cosmetic industry.

Magnetic silica surface functionalized palladium catalyst: A modular approach for C-C cross-coupling reactions in water

A novel Pd immobilized catalyst has been prepared via surface modification of magnetic silica and characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), UV–Vis spectroscopy, X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) and inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The prepared composite material found to be highly efficient and recyclable heterogeneous catalyst for the Suzuki coupling reaction in aqueous medium with high turnover number (TON) of 1138 and turnover frequency (TOF) of 2276 h−1. The Pd content of the catalyst was 0.09 mol% and afforded excellent to good yield of biaryls from a wide variety of aryl halides, including electron- withdrawing and releasing groups. The catalyst was reused up to six cycles with 97% efficiency for the Suzuki coupling reaction.

Catalytically Active Gold Nanomaterials Stabilized by N-heterocyclic Carbenes.

Solid supported or ligand capped gold nanomaterials (AuNMs) emerged as versatile and recyclable heterogeneous catalysts for a broad variety of conversions in the ongoing catalytic ′gold rush′. Existing at the border of homogeneous and heterogeneous catalysis, AuNMs offer the potential to merge high catalytic activity with significant substrate selectivity. Owing to their strong binding towards the surface atoms of AuMNs, NHCs offer tunable activation of surface atoms while maintaining selectivity and stability of the NM even under challenging conditions. This work summarizes well‐defined catalytically active NHC capped AuNMs including spherical nanoparticles and atom‐precise nanoclusters as well as the important NHC design choices towards activity and (stereo‐)selectivity enhancements.

Palladium nanoparticles supported by functionalized metal-organic framework: an excellent recyclable heterogeneous catalyst for the synthesis of commercially important rose essence, 2-phenyl ethanol

Palladium nanoparticles on ethylenediamine-grafted functionalized chromium-based metal organic framework (Pd-ED-MIL-101) was tested for the hydrogenation of styrene oxide to 2-phenylethanol, the key ingredient of the rose essence. The catalyst was found as an excellent heterogeneous recyclable catalyst for selective hydrogenation of styrene oxide to 2-phenylethanol (100% conversion and ∼100% selectivity) within 2 h in methanol with a catalyst loading only 0.25 mol % palladium at ambient pressure and temperature under molecular hydrogen. If the catalyst loading increases to 0.50 mol % palladium, the conversion time reduces to 1 h. In repeated runs (tested for 5 cycles) showed no loss of activity and selectivity of the catalyst. To the best of our knowledge, the performance of the present catalyst is one of the best compared to all other reported catalysts in terms of conversion, selectivity, reaction time, reaction conditions, purification, catalyst stability, catalyst loading, catalyst recyclability, safety and convenience.

Efficient and Recyclable Heterogeneous Catalyst Based on PdNPs Stabilized on a Green-Synthesized Graphene-like Nanomaterial: Effect of Surface Functionalization.

This work reports for the first time a straightforward and efficient approach to covalent surface functionalization of a sustainable graphene-like nanomaterial with abundant carboxylic acid groups. This approach results in an efficient and robust chelatant platform for anchoring highly dispersed ultrasmall palladium particles with excellent catalytic activity in the reduction of both cationic (methylene blue, MB) and anionic (eosin-Y, Eo-Y) toxic organic dyes. The large-specific-surface-area (SBET = 266.94 m2/g) graphene-like nanomaterial (GHN) was prepared through a green and cost-effective pyrolysis process from saccharose using layered bentonite clay as a template. To introduce a high density of carboxylic acid functions, GHN was first doubly functionalized by successive grafting reaction using two different strategies: (i) in the first case, GHN was first grafted by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) and then bifunctionalized by chemical grafting of tris(4-hydroxyphenyl)methane triglycidyl ether (TGE). In the second case, the grafting order of the two molecules has been reversed. GHN-GPTMS-TGE provided the highest number of grafted reactive epoxy groups, and it was selected for further functionalization with carboxylic acid functions via a ring-opening reaction through a two-step hydrolysis (H2SO4)/oxidation (KMnO4) approach. The GHN nanomaterial bearing carboxylic acid groups was then treated with sodium hydroxide to produce a deprotonated carboxylic acid-rich platform. Finally, due to a high density of accessible chelatant carboxylic acid groups, GHN-COO- binds strongly a great amount of Pd2+ ions to form stable complexes which after reduction by NaBH4 leads to highly dispersed, densely anchored, and uniformly distributed nanoscale Pd particles (d ∼ 4.5 nm) on the surface of the functionalized GHN. The GHN-COO-@PdNPs nanohybrid proved to be highly efficient for dye reduction by NaBH4 in aqueous solution at room temperature. Moreover, because of the high stability of the as-prepared graphene-like supported PdNPs, it exhibited very good reusability and could be recycled up to eight times without any significant loss in activity.

Magnetically Recyclable Heterogeneous Cobalt Ferrite Catalyst for the Direct N‐Alkylation of (Hetero)aryl Amines with Alcohols

AbstractHerein we report the use of spinel cobalt ferrite nanoparticles as an efficient and selective catalyst for the mono N‐alkylation of aryl and hetero aryl amines with various aromatic and aliphatic alcohols. Based on our experiments, the optimum condition for good to excellent yield were observed with alcohol (1.0 mmol), aniline (1.2 mmol), KOH (0.5 equiv), and CoFe2O4 nanocatalyst (10 mol%) in toluene at 130 °C in 24 hours. Further control experiment studies revealed that the reaction does not proceed in the absence of the catalyst or a strong base. This magnetically recyclable nanocatalyst does not require any ligands and is easily synthesized at low temperature. The reutilization of the recovered catalyst in a fresh reaction gave good to excellent yield. The experiment results strongly suggest a borrowing hydrogen pathway for N‐alkylation under our standard conditions. The utility of these nanocatalysts was also demonstrated for the dehydrogenative synthesis of heterocycles like indole and quinolines.

Facile N‐Formylation of Amines on Magnetic Fe3O4−CuO Nanocomposites

AbstractA facile, eco‐friendly, efficient, and recyclable heterogeneous catalyst is synthesized by immobilizing copper impregnated on mesoporous magnetic nanoparticles. The surface chemistry analysis of Fe3O4−CuO nanocomposites (NCs) by XRD and XPS demonstrates the synergistic effect between Fe3O4 and CuO nanoparticles, providing mass‐transfer channels for the catalytic reaction. TEM images clearly indicate the impregnation of CuO onto mesoporous Fe3O4. This hydrothermally synthesized eco‐friendly and highly efficient Fe3O4−CuO NCs are applied as a magnetically retrievable heterogeneous catalyst for the N‐formylation of wide range of aliphatic, aromatic, polyaromatic and heteroaromatic amines using formic acid as a formylating agent at room temperature. The catalytic activity of the NCs for N‐formylation is attributable to the synergistic effect between Fe3O4 and CuO nanoparticles. The N‐formylated product is further employed for the synthesis of biologically active quinolone moieties.

Development of N,N-disulfo-1,1,3,3-tetramethylguanidinium Chlorometallates as Heterogeneous Catalysts for One Pot Synthesis of 1,2-dihydro-1- aryl-3H-naphth[1, 2-e][1,3]oxazin-3-one Derivatives

Background: Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 -, Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for threecomponent synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones. Methods: N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3-tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst. Results: The characterization of synthesized chlorometallates was done using spectroscopic and other analytical techniques, including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study. Conclusion: A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4-/Zn2Cl6 2-/NiCl4 2-/MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as an efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2-dihydro-1-aryl-3Hnaphth[ 1,2-e][1,3]oxazin-3-ones in neat condition.

Copper(0) nanoparticles immobilized on SBA-15: A versatile recyclable heterogeneous catalyst for solvent and ligand free C–S coupling reaction from diverse substrates

Thioester is a vital part of several commercially available drugs. Consequently, development of suitable low cost catalyst for C–S bond formation is extremely necessary. In present work, we report a SBA-15 supported copper(0) nanoparticles based catalyst (Cu(0)MS) using wet impregnation method. The catalyst was thoroughly characterized by several techniques including powder X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), transmission electron microscopy (TEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and inductively coupled plasma-optical emission spectrometry (ICP-OES). This mesoporous silica supported copper(0) nanoparticles have been exploited as a catalyst for ligand-free and solvent-free C–S cross-coupling reactions. Symmetrical/unsymmetrical aryl/alkyl sulphides have been synthesized by the S-arylation of aromatic, heteroaromatic, and aliphatic thiols with aryl, heteroaryl as well as vinyl halides. Aryl chlorides also responded the reaction very well to produce aryl sulfides. The applicability of the current protocol has also been explored for the synthesis of the starting materials of different C–S bond containing pharmaceuticals. In addition, the present catalytic system is also suitable for the synthesis of a variety of symmetrical diaryl sulphides from aryl halides using thiourea as a sulfur source. Furthermore, it was also found that the Cu(0)MS catalyst can be reused five times without substantial loss in activity. • SBA-15 supported copper(0) nanoparticle. • Ligand-free and solvent-free C–S cross-coupling reaction. • Diverse substrates scope including vinyl halides. • Gram scale synthesis of the key structures of commercially available C–S bond containing drugs. • Symmetrical diaryl sulphides from aryl halides and thiourea.

Facile one-step synthesis of 3D honeycomb-like porous chitosan bead inlaid with Mn[sbnd]Fe bimetallic oxide nanoparticles for enhanced degradation of dye pollutant

Developing a sustainable, efficient and recyclable heterogeneous Fenton-like catalyst is important to wastewater treatment. Herein, well-dispersed MnO2 and Fe3O4 nanoparticles inlaid in chitosan beads (MnO2-Fe3O4/CH) was firstly fabricated and employed in the degradation of methylene blue (MB). The bead was prepared via a facile one-step method by dropwise addition of chitosan-metal salt solution into alkaline solution. Comparing with monometallic chitosan beads (MnO2/CH, Fe3O4/CH) and naked MnO2-Fe3O4, MnO2-Fe3O4/CH displayed significantly higher activity for MB degradation with the assistance of hydrogen peroxide (H2O2), finally removing 96.8% MB under the optimal conditions (50 mg L−1 MB, 4.0 g L−1 catalyst, 30 g L−1 H2O2, pH = 7, 60 min). Based on a series of characterizations, the large surface area (60.1 m2 g−1), well-developed porosity (0.3 cm3 g−1), and intensified electron transport of MnO2-Fe3O4/CH consequently enhanced the catalytic performance via a synergistic effect. Because the specific porous structure of MnO2-Fe3O4/CH facilitated the adsorption/diffusion of reactants and exposure of active sites. Meanwhile, the electron transfer from Mn3+ to Fe3+ accelerated the Fe3+/Fe2+ cycle, which favored the production of dominant reactive species hydroxyl radical for MB degradation. Besides, the magnetic beads could be easily collected from the solution and reused for five times with a negligible leaching.

Rosin-based porous heterogeneous catalyst functionalized with hydroxyl groups and triazole groups for CO2 chemical conversion under atmospheric pressure condition

Development of efficient, green and recyclable heterogeneous catalysts for the chemical conversion of CO2 into cyclic carbonates with excellent yields under atmospheric pressure condition is still a very challenging task. Herein, a class of biomass-derived hyper-cross-linked porous heterogeneous catalysts MPAc-Br and MPAc-OH-Br, based on easily available and sustainable rosin, was synthesized by Friedel–Crafts polymerization and the further N-alkylation of triazole groups. Compared with MPAc-Br, the bifunctional catalyst MPAc-OH-Br (bearing triazole IL groups and -OH groups) exhibited higher catalytic activity for direct chemical conversion of CO2 into cyclic carbonates (up to 99% yields) under metal-, solvent-free and atmospheric pressure conditions. The rosin-based porous molecular structure and bifunctional groups on the surface of MPAc-OH-Br played a very important role in the promoting the cycloaddition of CO2 with epoxides under the optimal conditions. Furthermore, MPAc-OH-Br exhibited good stability and reusability (96% yield after 10 recycles).

Silica supported dodecatungstophosphoric acid (DTP/SiO2): An efficient and recyclable heterogeneous catalyst for rapid synthesis of quinoxalines

A facile synthesis of quinoxalines by the cyclocondensation of substituted phenacyl bromides with o-pheneylenediamines using silica-supported dodecatungstophosphoric acid (DTP/SiO2) as a recyclable heterogeneous catalyst is unveiled in this research work. This method is practicable due to environmentally benign, easy workup, high yield, less reaction time, low cost, mild reaction condition, and recyclable heterogeneous catalyst. The catalyst can be easily recovered from the reaction mixture only by filtration and reused up to five catalytic cycles without significant loss of catalytic activity and product yield. This leads to making the process more affordable.

Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols.

Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.

Perlite impregnated with HPA/α-Fe2O3: Magnetically separable catalyst for the synthesis of 3,3,6,6-tetramethyl-9-substituted-3,4,6,7-tetrahydro-2H-xanthene-1,8-(5H,9H)-diones

Phosphotungstic acid (HPA)/α-Fe2O3-loaded Perlite has been prepared as a recyclable heterogeneous catalyst for the synthesis of xanthenes. The prepared catalyst has been characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM) with selected-area electron diffraction (SAED) pattern analysis, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) measurements. XRD peaks at 2θ = 9.08° and 26.73° (HPA) and 36.03°, 39.72°, and 62.6° (α-Fe2O3) showed efficient loading of HPA/α-Fe2O3 on the Perlite surface. TEM images of the prepared HPA/α-Fe2O3/Perlite corroborated the successful loading of α-Fe2O3 on the Perlite. Advantages of this new protocol include facile handling, low cost, easy work-up procedure, and remarkable reusability over several cycles without loss of the catalytic activity.