Tianbin Wu

MOF-5/n-Bu4NBr: an efficient catalyst system for the synthesis of cyclic carbonates from epoxides and CO2 under mild conditions

The development of efficient heterogeneous catalysts for the cycloaddition of CO2 with epoxides to produce five-membered cyclic carbonates under mild reaction conditions is of great importance. In this work, the coupling reaction of CO2 with propylene oxide (PO) to produce propylene carbonate (PC) catalyzed by MOF-5 (metal-organic frameworks) in the presence of quaternary ammonium salts (Me4NCl, Me4NBr, Et4NBr, n-Pr4NBr, n-Bu4NBr) was studied in different conditions. It was discovered that MOF-5 and quaternary ammonium salts had excellent synergetic effect in promoting the reaction, and the MOF-5/n-Bu4NBr catalytic system was the most efficient among them. The optimal temperature for the reaction was around 50 °C. The reaction could be completed in 6 h at low CO2 pressure with very high selectivity. A decrease of the yield of PC was not noticeable after MOF-5 was reused three times, indicating that the MOF-5 was stable. The MOF-5/n-Bu4NBr catalytic system was also very active and selective for the cycloaddition of CO2 with other epoxides, such as glycidyl phenyl ether, epichlorohydrin and styrene oxide. The mechanism for the coupling reaction is also discussed.

Ru nanoparticles immobilized on metal–organic framework nanorods by supercritical CO2-methanol solution: highly efficient catalyst

A simple and efficient route for the immobilization of noble metal nanoparticles onto metal–organic framework (MOF) has been designed in this work. The Ru/MOF nanocomposites were prepared using RuCl3·3H2O as a precursor in supercritical CO2-methanol solution at 200 °C. The as-synthesized Ru/MOF composite presented a high catalytic performance for the hydrogenation of cyclohexene and benzene. There was almost no activity loss after the catalyst was reused five times. The intermolecular interactions between the MOF and Ru nanoparticles were investigated by X-ray photoelectron spectra and FT-IR spectra. It was shown that the carboxylate groups of MOF were coordinated to Ru. The formation mechanism of the Ru/MOF nanocomposites in supercritical CO2-methanol solution through an inorganic reaction route was discussed. This method can be easily applied to the synthesis of other MOF-supported metal nanoparticles.

One-step synthesis of highly efficient nanocatalysts on the supports with hierarchical pores using porous ionic liquid-water gel.

Stable porous ionic liquid-water gel induced by inorganic salts was created for the first time. The porous gel was used to develop a one-step method to synthesize supported metal nanocatalysts. Au/SiO2, Ru/SiO2, Pd/Cu(2-pymo)2 metal-organic framework (Cu-MOF), and Au/polyacrylamide (PAM) were synthesized, in which the supports had hierarchical meso- and macropores, the size of the metal nanocatalysts could be very small (<1 nm), and the size distribution was very narrow even when the metal loading amount was as high as 8 wt %. The catalysts were extremely active, selective, and stable for oxidative esterification of benzyl alcohol to methyl benzoate, benzene hydrogenation to cyclohexane, and oxidation of benzyl alcohol to benzaldehyde because they combined the advantages of the nanocatalysts of small size and hierarchical porosity of the supports. In addition, this method is very simple.

Preparation of Catalytic Materials Using Ionic Liquids as the Media and Functional Components

Ionic liquids (ILs) have attracted much attention due to their unique properties and wide application potential in a variety of fields. The unusual properties of ILs provide numerous opportunities to design and prepare arious advanced materials, including highly efficient catalysts. In recent years, synthesis of different kinds of catalytic materials and their applications in chemical reactions have been studied extensively and have become a very interesting area. Herein, we present a review on the synthesis of catalytic materials using ILs as the media and/or functional components; the important and widely investigated topics are discussed, including mainly metal nanocatalysts/IL, functional IL/support, metals or metal oxides/IL/support, polymeric ILs (PILs) catalysts, and the performances of catalytic systems are highlighted. An outlook for this interesting area is also given at the end of the article.

Facile one-pot synthesis of VxOy@C catalysts using sucrose for the direct hydroxylation of benzene to phenol

VxOy@C catalysts were prepared from sucrose and NH4VO3 by a one-pot hydrothermal method. They showed satisfactory catalytic performance for the hydroxylation of benzene to phenol in acetonitrile using oxygen as the oxidant.

Shape controlled synthesis of palladium nanocrystals by combination of oleylamine and alkylammonium alkylcarbamate and their catalytic activity

The shape of Pd nanocrystals (NCs) can be controlled by combination of oleylamine (OAm) and alkylammonium alkylcarbamate (AAAC), and Pd spheres, tetrahedra and multipods have been synthesized. The multipods and tetrahedra are much more active than the spheres for hydrogenation reactions.

Ru–Zn supported on hydroxyapatite as an effective catalyst for partial hydrogenation of benzene

Design and preparation of efficient and greener catalytic systems for partial hydrogenation of benzene to cyclohexene is an interesting topic in green chemistry. In this work, Ru and Ru–Zn catalysts supported on hydroxyapatite (HAP), which is nontoxic and abundant in nature, were prepared via the simple ion-exchange method. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron spectroscopy (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption–desorption methods. The influences of Ru/Zn molar ratio, reaction temperature, pressure, reaction time, and amount of modifier NaOH on the partial hydrogenation of benzene were studied in detail. It was demonstrated that metallic nanoparticles of less than 2 nm were dispersed uniformly on the surface of the HAP, and the bimetallic Ru–Zn/HAP catalysts showed high activity and selectivity. The yield of cyclohexene could reach 33% over Ru–Zn/HAP at the optimized conditions, and the catalyst could be reused at least four times without obvious loss of the activity and selectivity.

Highly selective benzene hydrogenation to cyclohexene over supported Ru catalyst without additives

The Ru/ZnO–ZrOx(OH)y catalyst is very efficient for the selective hydrogenation of benzene to cyclohexene, and the yield of cyclohexene can reach 56% without using any additive. This work provides a highly efficient, cheap and clean method to produce cyclohexene.

Highly selective oxidation of cyclohexene to 2-cyclohexene-1-one in water using molecular oxygen over Fe–Co–g-C3N4

Efficient and greener oxidation of cyclohexene to 2-cyclohexene-1-one is an interesting topic. In this work, we prepared a series of Fe–Co doped graphitic carbon nitride (Fe–Co–g-C3N4) catalysts through simple impregnation and calcination methods. The catalysts were characterized by different techniques, such as transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption–desorption measurement, powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The selective oxidation of cyclohexene to 2-cyclohexene-1-one was carried out in different solvents over the catalysts using molecular oxygen as an oxidant. The influence of supports, solvents, Fe/Co molar ratio in the catalysts, pressure of oxygen, reaction temperature and time of the reaction was investigated. It was revealed that the bimetallic Fe–Co–g-C3N4 catalysts were very efficient for the reaction. More interestingly, the selectivity of the reaction in water was much higher than that in other solvents. Under optimized conditions, the selectivity to 2-cyclohexene-1-one could reach 95% at a cyclohexene conversion of 36%. The Fe–Co–g-C3N4 catalyst could be reused at least four times without obvious loss of efficiency.

Cross-linked polymer coated Pd nanocatalysts on SiO2 support: very selective and stable catalysts for hydrogenation in supercritical CO2

Using greener solvents, enhancing the selectivity and stability of catalysts is an important aspect of green chemistry. In this work, we developed a route to immobilize Pd nanoparticles on the surface of silica particles with cross-linked polystyrene coating by one-step copolymerization, and Pd(0) nanocatalysts supported on the silica particle supports with cross-linked polystyrene coating were successfully prepared. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), plasma optical emission spectroscopy, and thermogravimetric analysis (TGA), and were used for hydrogenation of 2,4-dimethyl-1,3-pentadiene to produce 2,4-dimethyl-2-pentene and allyl alcohol to produce 1-propanol. It was found that the selectivity of the reaction was enhanced significantly by the polymer coating, and the catalysts were very stable due to the insoluble nature of the cross-linked polymers. Supercritical (sc)CO2 can accelerate the reaction rates of the reactions catalyzed by the specially designed catalysts significantly. The excellent combination of polymer coating and scCO2 has wide potential applications in catalysis.