Robust Heterogeneous Catalyst Research Articles

Advancing Sustainable Manufacturing through a Heterogeneous Cobalt Catalyst for Selective C–H Oxidation

An increasingly important chemical transformation that will be necessary as we move toward sustainable manufacturing is the oxidation of C–H bonds. Our reported robust heterogeneous cobalt water oxidation catalyst, formed from a metal carbonyl phosphine complex as precursor, is now shown to be active for the selective oxidation of C–H bonds. Of 10 oxidants tested, only Oxone and its oxidatively active component KHSO5 proved competent. A wide variety of substrates were effectively oxidized with KHSO5, including heterocycles, alkyl arenes, alcohols, alkenes, and alkanes. The catalyst is highly selective for C–H bonds over water oxidation when the reaction is conducted in aqueous media. The catalyst can be recycled with minimal loss of activity while under N2. Preliminary mechanistic data are also discussed.

Modified Montmorillonite Clay Stabilized Silver Nanoparticles: An Active Heterogeneous Catalytic System for the Synthesis of Propargylamines

We have synthesized size selective silver nanoparticles (Ag-NPs) in the nanopores of modified montmorillonite clay by an “in situ” approach. The modification of montmorillonite K-10 was carried out with HCl under controlled condition for generating a high surface area and porous matrix which acted as hosts for the “in situ” generation of silver nanoparticles. The synthesized nanocomposite material was well characterized by UV–Visible spectroscopy, powder XRD, N2 adsorption–desorption isotherm and TEM analysis. UV–Visible and TEM study revealed silver nanoparticles of 0–10 nm were evenly distributed on the support. The Ag-NPs stabilized on modified montmorillonite serves as an efficient green heterogeneous catalyst for the three component one-pot synthesis of propargylamines with 83–95 % yield and 100 % selectivity under mild reaction condition. The nanocatalyst can be recycled several times without any significant loss in its catalytic activity. Ag-NPs@mmt is found to be an efficient and robust heterogeneous catalyst for the synthesis of propargylamines under mild reaction condition.

1604096: CeO2 nanoparticles: a robust and reusable heterogeneous catalyst for the diastereoselective synthesis of β-acetamido esters – ESI

1604096: CeO2 nanoparticles: a robust and reusable heterogeneous catalyst for the diastereoselective synthesis of β-acetamido esters – ESI

1604096: CeO2 nanoparticles: a robust and reusable heterogeneous catalyst for the diastereoselective synthesis of β-acetamido esters – ESI

1604096: CeO2 nanoparticles: a robust and reusable heterogeneous catalyst for the diastereoselective synthesis of β-acetamido esters – ESI

Sustainable synthesis of sulfonamides using supported ionic liquid phase catalyst containing Keggin‐type anion

A silica‐supported ionic liquid phase catalyst containing Keggin‐type anion has been prepared by covalent grafting of ferrocene‐tagged ionic liquid in a matrix of silica followed by anion metathesis reaction. This novel catalyst served as a robust heterogeneous catalyst for the synthesis of biologically active sulfonamides from 4‐toluenesulfonyl chloride and amines. Additionally, recycling experiments showed that the catalyst could be reused five times. Copyright © 2015 John Wiley & Sons, Ltd.

One-pot sonochemical synthesis of 1,3-thiazolidin-4-ones using nano-CdZr4(PO4)6 as a robust heterogeneous catalyst

An efficient three-component synthesis of 1,3-thiazolidin-4-ones is described by one-pot condensation of aldehydes, aniline and thioglycolic acid with nano-CdZr4(PO4)6 as a robust heterogeneous catalyst under ultrasonic irradiation. Use of simple and readily available starting materials, experimental simplicity, applying the sonochemical methodology as an efficient method and innocuous means of activation in synthetic chemistry are some advantages of this protocol.

Integrated Process of Aerobic Oxidation–Olefination–Asymmetric CC Bond Formation Catalyzed by Robust Heterogeneous Gold/Palladium and Chirally Modified Rhodium Nanoparticles

AbstractWe have achieved an integrated process of oxidation–olefination–asymmetric 1,4‐addition reactions under aerobic and aqueous conditions using metal nanoparticles as robust heterogeneous catalysts. A tandem process of aerobic oxidation and Horner–Wadsworth–Emmons olefination was successfully catalyzed by gold/palladium bimetallic nanoparticles. A wide range of substrates gave the desired products in high yields and excellent selectivities. This tandem process was further connected with an asymmetric 1,4‐addition reaction catalyzed by chiral rhodium nanoparticles to achieve a challenging three‐step, one‐pot sequential reaction. Various types of esters with a chiral center at the β‐position were obtained from readily available and stable alcohols and arylboronic acids in high yields with high enantioselectivities in a one‐pot sequential reaction integrating three transformations.magnified image

Bioinspired Nanoparticle‐Assembly Route to a Hybrid Scaffold: Designing a Robust Heterogeneous Catalyst for Asymmetric Dihydroxylation of Olefins

AbstractA hierarchical polyamine‐silica structure is shown to encase osmate ions resulting in robust and reusable catalysts for asymmetric dihydroxylation of olefins with a high TON (>700). Whilst the polypeptide and related polyamines resembling a proteinaceous matrix in biosilica nanostructures preserve the osmate as the active centre, the surrounding assembly of silica nanoparticles imparts stability and textural properties to the catalyst. This confinement of osmate in the microsphere leads to higher catalytic activity and enantioselectivity for a variety of olefins as the substrate. The hybrid nature of the catalyst not only allows for the usage of various solvent systems, but also provides a means to be integrated with multi‐components/functions for tuning the activity, catalysis separation and reusability. Interestingly, the presence of polyamine makes the catalyst retain its activity even in the presence of chelating acids like citrate that are known to diminish enantioselectivity.

Ultradispersed Palladium Nanoparticles in Three-Dimensional Dendritic Mesoporous Silica Nanospheres: Toward Active and Stable Heterogeneous Catalysts.

Immobilization of highly monodispersed palladium nanoparticles in colloidal mesoporous silica supports has been successfully achieved. The Pd nanoparticles with a uniform small size of ∼1.2 nm can be homogeneously distributed in individual mesopore channels of amino group-functionalized three-dimensional dendritic mesoporous silica nanospheres (3D-dendritic MSNSs) with a Pd content of ∼2.8%. The 3D-dendritic MSNSs-based nanoreactors show high activity in Suzuki-Miyaura cross-coupling reactions of bromobenzene with phenylboronic acid, obtaining a yield over 99% with 0.075 mol % Pd catalyst at room temperature in the dark within 12 h. More importantly, the excellent catalytic performance can be maintained with a negligible decrease lasting at least six cycles. It further reveals that the mesoporous frameworks of the colloidal silica supports can be well-preserved after four catalytic runs; meanwhile, the Pd nanoparticles in the mesopore channels also can remain the sizes of 1.5±0.3 nm without significant transfer and aggregation. The unique mesostructure of the 3D-dendritic MSNSs with mesopore channels of short length and large diameter is supposed to be the key role in immobilization of active and robust heterogeneous catalysts, and it would have more hopeful prospects in catalytic applications.

Four alkoxohexavanadate-based Pd-polyoxovanadates as robust heterogeneous catalysts for oxidation of benzyl-alkanes.

Four alkoxohexavanadate-based Pd-POVs [Pd(dpa)(acac)]2[V6O13(OMe)6] (1), [Pd(dpa)(acac)]2[V6O11(OMe)8] (2), [Pd(dpa)(acac)]2[V6O11(OMe)8]·H2O (3), and [Pd(DMAP)2(acac)]2[V6O11(OMe)8]·H2O (4) (POV = polyoxovanadate; dpa = 2,2'-dipyridine amine; DMAP = 4-dimethylaminopyridine; acac = acetylacetone anion) have been synthesized and fully characterized by single crystal X-ray diffraction and powder X-ray diffraction analyses, Fourier transform infrared spectroscopy, element analyses, and X-ray photoelectron spectroscopy. In 1-4, Pd complexes and hexavanadate anions are assembled through electrostatic interactions. Interestingly, the [V6O11(OMe)8](2-) cores in 2 and 3 are a pair of isomers that can be isolated by controlling crystallization temperature. Moreover, to the best of our knowledge, the {V6} core in 3 represents a new octamethoxyhexavanadates cluster. It is notable that compounds 1-4 exhibit excellent heterogeneous catalytic performance in the oxidation of benzyl-alkanes with t-butylhydroperoxide as oxidant. Among them, the catalytic activity of 1 (conv. and selec. up to 99%, respectively) outperforms others and can be reused without losing its activity.

Copper loaded cross-linked poly(ionic liquid): robust heterogeneous catalyst in ppm amount

A novel heterogeneous copper catalyst was synthesized in which poly(1-vinyl imidazole-co-ionic liquid) was used as a solid heterogeneous support.

Copper-loaded polymeric magnetic nanocatalysts as retrievable and robust heterogeneous catalysts for click reactions

A novel heterogeneous copper catalyst based on poly(ionic liquid)-coated magnetic nanoparticles was prepared by the polymerization of 3-carboxymethyl-1-vinylimidazolium in the presence of surface-modified magnetic nanoparticles, followed by the coordination of the carboxylate units in the polymer chains with copper sulfate.

Polystyrene resin-supported CuI-cryptand 22 complex: a highly efficient and reusable catalyst for three-component synthesis of 1,4-disubstituted 1,2,3-triazoles under aerobic conditions in water

Polystyrene resin-supported copper(I) iodide-cryptand-22 complex (PS–C22–CuI) was synthesized and characterized by FT-IR, EDX, SEM, XPS, and TG-DTA analysis. This complex was found to be a highly active and robust heterogeneous catalyst for either three-component reaction of organic halides, sodium azide, and terminal alkynes, or the reaction of organic azides and alkynes to form 1,4-disubstituted 1,2,3-triazoles in good to excellent yields at room temperature, using water as the green solvent. The catalyst can be not only easily isolated from the final product by filtration but also reused without significant loss of catalytic activity.

ChemInform Abstract: Robust Heterogeneous Nickel Catalysts with Tailored Porosity for the Selective Hydrogenolysis of Aryl Ethers.

AbstractSiC materials with tailored porosity and integrated Ni‐nanoparticles are synthesized and their catalytic activity for the hydrogenolytic cleavage of different phenyl ethers is examined.

Ligand-free direct C-arylation of heterocycles with aryl halides over a metal-organic framework Cu2(BPDC)2(BPY) as an efficient and robust heterogeneous catalyst

A crystalline porous metal-organic framework Cu2(BPDC)2(BPY) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu2(BPDC)2(BPY) exhibited high catalytic activity in direct CH arylation reactions between heterocyles and aryl halides. The Cu2(BPDC)2(BPY)-catalyzed CH arylation reaction could proceed to higher conversion than that of the reaction using Cu3(BTC)2, Cu(BDC), Cu(BPDC), and Cu2(BDC)2(BPY) as catalyst. Furthermore, under our conditions, the Cu2(BPDC)2(BPY) also exhibited significantly higher activity than that of common copper salts, including Cu(NO3)2, CuCl, CuCl2, and CuI. Excellent reusability of the Cu-MOF in the direct heterocycle CH arylation reaction was achieved.

Robust Heterogeneous Nickel Catalysts with Tailored Porosity for the Selective Hydrogenolysis of Aryl Ethers

AbstractSiC materials with tailored porosity and integrated Ni NPs (Ni@SiC) were synthesized via microphase separation of polycarbosilane‐block‐polyethylene followed by its pyrolysis. Changing the length of organic block allowed the synthesis of micro, meso and hierarchical Ni@SiC materials which were characterized by PXRD, TEM, TGA, and nitrogen physisorption. Selective hydrogenolysis of aryl ethers mimicking the most abundant linkages of lignin was achieved in water avoiding the possible hydrogenation of aromatic rings.

Surface Functionalization of Supported Mn Clusters to Produce Robust Mn Catalysts for Selective Epoxidation

A robust heterogeneous Mn catalyst for selective epoxidation was prepared by the attachment of a Mn4 oxonuclear complex [Mn4O2(CH3COO)7(bipy)2](ClO4)·3H2O (1) on SiO2 and the successive stacking of SiO2-matrix overlayers around a supported Mn cluster. The structures of supported Mn catalysts were characterized by means of FT-IR spectroscopy, diffuse-reflectance UV/vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and Mn K-edge X-ray absorption fine structure. A ligand exchange reaction between the CH3COO ligand of 1 and surface silanol group produced a SiO2-supported Mn cluster (2), whose coordination structure was similar to 1. Subsequent heating of 2 under vacuum yielded supported Mn clusters (3, 4) through the partial elimination of CH3COO ligands. The surface-attached Mn clusters of 2, 3, and 4 were easily released to a reaction solution under epoxidation conditions (Mn leaching: approximately 50%), although they were active for epoxidation of trans-stilbene (the conversion of trans-stilbene, 99%, and the selectivity of trans-stilbene epoxid, 96%, for 6 h on 3). We found that the functionalization of the supported Mn cluster on 2 with surface SiO2-matrix overlayers altered the reactivity of the supported Mn cluster. Dimeric Mn species (5c) with reduced Mn oxidation state and coordination numbers was formed together with a reaction nanospace surrounded by the SiO2-matrix overlayers. By optimizing the stacking manner of the SiO2-matrix overlayers, the durability of the Mn catalyst was remarkably improved from leaching (the Mn leaching reached the minimum value of 0.01%), and active and stable epoxidation performances were successfully achieved in the heterogeneous phase (the conversion of trans-stilbene, 97%, and the selectivity of trans-stilbene epoxide, 91%, for 31 h on 5c).

Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes

Abstract Rhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

Two-dimensional copper-based metal–organic framework as a robust heterogeneous catalyst for the N-arylation of imidazole with arylboronic acids

N-arylation of imidazole was accomplished with a two-dimensional (2D) [Cu(ima)2]n metal–organic framework in methanol at room temperature. A variety of N-arylimidazoles were isolated in good yields after a short reaction time. Moreover, the robust MOF may be readily recovered after the reaction and reused for many cycles without loss of catalytic activity.

Multiple Oxo-Vanadium Schiff Base Containing Cyclotriphosphazene as a Robust Heterogeneous Catalyst for Regioselective Oxidation of Naphthols and Phenols to Quinones

Grafting of multiple oxo-vanadium Schiff base moieties to cyclotriphosphazene provided an efficient and recyclable heterogeneous catalyst for the regioselective oxidation of naphthols and phenols to quinones by using t-butylhydroperoxide as oxidant. One of the main advantages of the developed catalyst was the presence of multiple oxo-vanadium moieties in close proximity which made the developed catalyst more active as compared to its homogeneous oxo-vanadium Schiff base. After the reaction, the catalyst was easily recovered from the reaction mixture by simple filtration and reused for five runs without loss in activity.