Preparation and characterization of a titanium(IV) silsesquioxane epoxidation catalyst anchored into mesoporous MCM-41.

This paper describes the synthesis and spectroscopic study of a titanium(IV) silsesquioxane complex, which is heterogenised in the pores of an MCM-41 host material. Its immobilization is performed via chemical bonding, not by means of physical adsorption. As a linking molecule between the MCM-41 carrier and the silsesquioxane, (3-glycidyloxypropyl)trimethoxysilane is used. Characterization is performed by using nitrogen adsorption techniques, TGA, diffuse reflectance infrared spectroscopy (DRIFT) and ICP-MS. Also its catalytic activity towards the epoxidation of alkenes shows interesting results.     

Amino groups immobilized on MCM-48: an efficient heterogeneous catalyst for the Knoevenagel reaction

Aminopropyl was grafted onto MCM-48 via post-synthesis methods. The aminopropyl-functionalized MCM-48 was found to be an effective base catalyst for Knoevenagel condensation.     

Diphosphino-functionalized MCM-41 anchored palladium(0) complex as an efficient catalyst for Heck arylation of conjugated alkenes with aryl halides

Diphosphino-functionalized MCM-41 anchored palladium(0) complex (denoted as MCM-41-2P-Pd(0)) was conveniently synthesized from commercially available and cheap γ-aminopropyltriethoxysilane via immobilization on MCM-41, followed by reacting with diphenylphosphinomethanol and palladium chloride and then the reduction with hydrazine hydrate. XRD and XPS spectroscopies were employed to characterize the title palladium complex. It was found that this complex is a highly active and stereoselective catalyst for Heck arylation of conjugated alkenes with aryl halides and can be reused many times without loss of activity.     

Synthesis of tetradentate N4 Schiff base dioxomolybdenum (VI) complex within MCM-41 as selective catalyst for epoxidation of olefins

Covalent grafting of MCM-41 with 3-chloropropyl trimethoxysilane and subsequent reactions respectively with pypr [N,N′-bis(2-pyrrolmethylidenaminopropyl)amine] and complexation with MoO₂(acac)₂ afforded MoO₂pyprMCM-41. X-ray diffraction and nitrogen sorption analyses revealed the preservation of the textural properties of the support as well as accessibility of the channel system despite sequential reduction in surface area, pore volume and pore size. Elemental analyses showed nearly complete complexation of the supported ligands and the presence of 0.24 mmol molybdenum per gram of the catalyst. Epoxidation of cyclooctene, cyclohexene, 1-hexene and 1-octene in the presence of MoO₂pyprMCM-41 with tert-butyl hydroperoxide (TBHP) were carried out with 21–98% conversion under the mild reaction conditions.     

Immobilization of new Mn(salen) complex over MCM-41 and its activity in asymmetric epoxidation of styrene

New tetradentate chelates of bis-Schiff bases were synthesized and then these chiral salen ligands were immobilized over mesoporous MCM-41 by using the ion-exchange method. The efficiency of the chiral catalyst was examined in the asymmetric epoxidation of styrene. Chiral Mn(salen) complexes immobilized onto mesoporous MCM-41 were stable during the reaction without any leaching and exhibited relatively high enantioselectivity for epoxidation as compared with homogeneous complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Schiff base complex of Cu immobilized on MCM-41 as reusable catalyst for efficient oxidative coupling of thiols and oxidation of sulfides using hydrogen peroxide

Schiff base complex of copper-functionalized MCM-41 (Cu-complex@MCM-41) was synthesized and used as an efficient and novel heterogeneous catalyst for the oxidative coupling of thiols into corresponding disulfides and oxidation of sulfides to sulfoxides using hydrogen peroxide (H₂O₂) as the oxidant. An aliphatic and aromatic series of sulfides and thiols including various functional groups were successfully converted into corresponding products. The all products were obtained in good to excellent yields. The mesoporous catalyst is characterized by FT-IR spectroscopy, BET, XRD, SEM, EDS and TGA. Recovery of the catalyst is easily achieved by simple filtration and reused for several consecutive runs without significant loss of its catalytic efficiency.     

Catalytic Oxidation of Alkylaromatics over Mesoporous (Cr)MCM-41

Liquid-phase catalytic oxidation of certain alkylaromatics over mesoporous (Cr)MCM-41 molecular sieves in the presence of chlorobenzene and tertiary butylhydroperoxide showed high substrate conversion and excellent product selectivity. The high catalytic activity of the materials is attributed to the complete oxidation of chromium ions to hexavalent chromium and the absence of pentavalent chromium in the mesoporous matrix.     

Co(II) coordinated metal-organic framework: An efficient catalyst for heterogeneous aerobic olefins epoxidation

An 8-connected, linear trinuclear cluster-based microporous metal organic framework (NH₄)₂[Co₃(Ina)(BDC)₃(HCOO)] (denoted as Co₃InaBDC₃, Ina = isonicotinate and BDC = 1,4-benzenedicarboxylate, CCDC is 935147) had been successfully synthesized by a facile hydrothermal synthesis method. The compound was extended through BDC linkers breadthwise and Ina linkers lengthways to the highly-connected framework. The Co₃InaBDC₃ was characterized through FT-IR, N₂ adsorption, XRD, TGA and SEM, and its characteristic structure was elucidated by single crystal X-ray diffraction. Using O₂ as oxidant, the Co₃InaBDC₃ was investigated as a good performed heterogeneous catalytic material for cyclooctene epoxidation. An extremely high turnover frequency (1370 h^− 1) for epoxycyclooctane was achieved, and Co₃InaBDC₃ exhibited excellent stabilities in 5 recycles without any loss of its catalytic performance.     

Ammonium decatungstocerate (IV): an efficient catalyst for ring opening of epoxides with aromatic amines

A mild, convenient and efficient ring opening of oxiranes with aromatic amines was catalyzed by ammonium decatungstocerate (IV) in acetonitrile. The reaction afforded the corresponding products in 92–100% yields. The catalyst was reused for several times with consistent activity.     

Zn-VCO3 hydrotalcite: A highly efficient and reusable heterogeneous catalyst for the Hantzsch dihydropyridine reaction

The Zn-VCO₃ hydrotalcite was found to be an excellent solid catalyst for the one-pot synthesis of triphenylpyridine-3,5-dicarboxamide via Hantzsch reaction of acetoacetanilide, ammonium hydroxide and various aromatic aldehydes. The combinatorial syntheses were achieved for the first time using hydrotalcite as a heterogeneous catalyst. The catalyst was active for the Hantzsch reaction in water at 60 °C. The products were isolated in good yields (85–93%) with short reaction times (2–3 h). The resulting substituted dihydropyridines were characterized and confirmed by ¹H and ¹³C NMR, FTIR, and HRMS spectral data and the solid catalyst was characterized by XRD, BET, SEM and TEM. The newly synthesized heterogeneous solid catalyst offers simple means for recovery and the isolated catalyst was reused for five rounds for the synthesis of compound 4a, without significant loss of catalytic activity. For all the other reactions carried out with the recycled catalyst, results were similar to with the fresh catalyst.     

Palladium(II) containing hydrotalcite as an efficient heterogeneous catalyst for Heck reaction

Palladium(II) containing hydrotalcite (Pd-HT) has been found to be an efficient and reusable catalyst in Heck reaction between aryl halides (X = Br, I) and olefins to give carbon–carbon coupled products in good to moderate yields.     

MCM-41-supported poly(γ-mercaptopropylsiloxane palladium(0)) complex as an efficient catalyst for Heck arylation of conjugated alkenes with aryl halides

MCM-41-supported poly(γ-mercaptopropylsiloxane palladium(0)) complex [MCM-41-SH-Pd(0)] was conveniently synthesized from commercially available and cheap γ-mercaptopropyltriethoxysilane via immobilization on MCM-41, followed by reacting with palladium chloride and then the reduction with hydrazine hydrate. XRD and XPS spectroscopy were employed to characterize the title palladium complex. It was found that this complex is a highly active and stereoselective catalyst for Heck arylation of conjugated alkenes with aryl halides and can be reused many times without loss of activity.     

环己烷催化氧化制环己酮的MCM-41催化剂研究

以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,采用水热合成法制备纯MCM-41分子筛和掺杂不同金属离子的MCM-41分子筛,并采用等体积浸渍法将一定量的金属离子负载在纯MCM-41分子筛内表面上,制备了负载型和掺杂型2类不同的MCM-41分子筛催化剂.分别考察了负载和掺杂的金属种类、金属Cr负载和掺杂量等对环己烷氧化制环己酮中的催化活性和选择性的影响.研究表明:采用掺杂制备的MCM-41分子筛催化剂活性明显高于负载型MCM-41分子筛催化剂;Cr掺杂量增加,虽然环己烷氧化转化率增加,但产物选择性下降;掺杂Cr的MCM-41分子筛催化剂,用于环己烷氧化制环己酮,在Si与Cr摩尔比为50以下、反应温度75℃、H2O2与环己烷摩尔比为1.2的条件下,环己烷的转化率可达60%左右,环己酮和环己醇的总选择性可达94%以上.     

Gold nanoparticles supported on mercaptoethanol directly bonded to MCM-41: An efficient catalyst for the synthesis of propargylamines

Mercaptofunctionalized MCM-41 (MCM-SH) was obtained via reaction of MCM-chloride with mercaptoethanol. Then, gold nanoparticles supported on MCM-SH (Au@HS-MCM nanocomposite) were prepared by chemical reduction of HAuCl₄ by NaBH₄. The obtained catalyst was used as an effective and reusable heterogeneous catalyst in three-component coupling of aldehydes, alkynes, and amines (A³-coupling) in water. The catalyst could be recovered and reused several times without a significant loss of activity.     

The use of palladium nanoparticles supported with MCM-41 and basic (Al)MCM-41 mesoporous sieves in microwave-assisted Heck reaction

A series of supported catalysts has been obtained by grafting of chemically generated palladium nanoparticles onto basic, Cs⁺ ion-exchanged molecular sieves (Al)MCM-41 and onto the non-basic, parent material MCM-41. Catalytic activity of the catalysts has been investigated in the Heck reaction between bromobenzene and butyl acrylate under microwave irradiation. The activity of the bifunctional catalysts (Pd@Cs⁺-(Al)MCM-41) and the activity of Pd@MCM-41 combined with sodium acetate as an external base were considerably higher under microwave irradiation than activities observed for the same catalytic systems under the conventional heating. The Pd@MCM-41/NaOAc system showed higher conversions than the bifunctional catalysts presumably due to a different nature and accessible amount of the base. On the other hand, microwave irradiation seems to increase the rate of aggregation of the metallic particles and thus also catalyst deactivation as compared with the usual heating.     

Synthesis and investigation of anchored copper (II) complexes within MCM-41 as selective catalysts for epoxidation of olefins

In the present study, preparation, characterization and catalytic activity of encapsulated copper (II) complexes within MCM-41 were investigated. The mesoporous molecular sieve MCM-41 was synthesized and grafted with 3-(trimethoxysilyl)-1-propanethiol to give a thiol modified material (MCM-41-S). The prepared material successively was reacted with acrylic acid and acrylonitrile to give AA-MCM-41 and AN-MCM-41, respectively. Using hexamethyldisilazane and copper (II) chloride, copper (II) complexes in the cavities of MCM-41 (Cu-AA-MCM-41 and Cu-AN-MCM-41) were prepared. The presence of copper (II) complex on the surfaces of host matrix and the structure of prepared catalyst is investigated by FT-IR, inductively coupled plasma-optical emission spectroscopy (ICP-OES), powder X-ray diffraction (XRD) and BET nitrogen adsorption–desorption methods. The catalytic activities of the catalysts were studied in epoxidation of olefins. The results showed that activities of the prepared catalysts (Cu-AA-MCM-41 and Cu-AN-MCM-41) and their selectivity to corresponding epoxides were more than those of MCM-41. In addition, the synthesized heterogeneous catalysts were truly reusable.     

Oxovanadium(IV) salicylidene Schiff base complex anchored on mesoporous silica MCM-41 as hybrid materials: a robust catalyst for the oxidation of sulfides

Oxovanadium(IV) Schiff base complex have been anchored onto the surface of purely siliceous MCM-41 and tested for its activity as catalyst for the oxidation of sulfides. This catalyst could alter this oxidation reaction extremity, exhibiting excellent yields with 100 % selectivity. The intercalation of the complex inside the silica matrix was supported by various characterization techniques like X-ray diffraction, differential thermogravimetric (TG-DTA), BET measurements, UV–Vis diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy (FT-IR). The stability of the catalyst during the course of the reaction was confirmed from its post catalytic FT-IR and XRD analysis. The catalyst could be reused five times without notable loss of its catalytic activity and efficiency which indicates that the metal-Schiff base moiety is intact and the coordination environments are not altered during the reaction.     

An efficient oxidation of cyclohexane over Au@TiO2/MCM-41 catalyst prepared by photocatalytic reduction method using molecular oxygen as oxidant

Cyclohexane oxidation using molecular oxygen as oxidant is one of the most challenge subjects. A novel photocatalytic reduction method to prepare Gold nanoparticles Au@TiO₂/MCM-41 was proposed. The prepared samples were characterized by XRD, N₂ adsorption isotherm, FT-IR, TEM and EDS. The results showed that gold nanoparticles were well-dispersed on TiO₂/MCM-41, and TiO₂ was dispersed on the surface of the support and the gold existed as Au⁰. Newly-developed catalyst was promising for the cyclohexane oxidation, achieving a turnover frequency (TOF) as high as 29,145 h^− 1 with 9.87% conversion of cyclohexane.     

Heterogeneous Fenton catalyst derived from hydroxide sludge as an efficient and reusable catalyst for anthraquinone dye degradation

Hydroxide sludge (HS) is the main by-product of drinking water production stations. In our work, we have promoted the valorization of these sludge, we convert it into activated carbon to serve as a support as a heterogeneous Fenton catalyst for reactive blue 19 (RB 19) degradation. The HS and Fe/HS-300 were characterized by means of SEM, EDX-ray, FTIR and XRD analysis. RB 19 and TOC removals were 92% and 41% respectively in optimal condition. More importantly, Fe/HS-300 exhibited an excellent stability and low Fe ion leaching (0.2–0.7mg/L), it was recycled 6 runs still maintaining the same efficiency.