Xia Chungu

Versatile MOF-derived cobalt catalyst for the reductive amination

The tunable metal center and the tailorable organic linker of metal-organic framework (MOF) make the characteristic of ultrahigh porosity, controllable pore size, crystalline nature and highly-ordered structures [1]. Since its emergence [2,3], it represents one of the most celebrated functional materials. Owing to the rich diversity of MOF family, a vast of important applications including the storage of gas, recognition of molecules as well as environment remediation have been developed [1,4]. Moreover, the extensive utilization of MOF as heterogeneous catalyst [5] and host matrices for immobilization of molecular catalysts [6] has demonstrated its versatility in applied catalysis. Meanwhile on the other aspect, as one of the well-established electrocatalysts for the oxygen reduction reaction [7], transition-metal nanoparticles (NPs) supported on nitrogen-doped carbon were groundbreakingly introduced into the liquid-phase catalytic hydrogenation and oxidation of organic molecules by the research group of Prof. Matthias Beller in Leibniz-Institut für Katalyse [8–10]. The nitrogen atoms implanted by pyrolyzing metal-phenanthroline complexes immobilized on support contributed to the catalytic reactivity of metal. Since then, these fascinating materials have enabled a series of progress for many important catalytic transformations [11,12]. Some insightful understandings about the effect of nitrogen atoms and metal cluster on catalytic performance have been revealed as well [13,14]. However, most of these catalysts exhibit poor reactivity and selectivity, challenging multicomponent synthetic organic reactions. To address this issue, Beller and co-workers developed MOF-derived cobalt NP catalyst supported on nitrogendoped carbon by taking full advantage of uniform topology and strong bonds between inorganic and organic units in MOF [15]. The nitrogen-contained cobalt MOF comprising two organic linkers 1,4-diazabicyclo[2.2.2] octane (DABCO) and terephthalic acid (TPA) was employed as structure directing template. The pyrolysis of in-situ assembled cobalt-DABCO-TPA MOF supported on carbon at 800°C under argon produced graphitic shell encapsulated cobalt nanoparticles (Fig. 1), which is the most active material. Characterization disclosed that there

Catalysis and applications of task-specific ionic liquids

Task-specific ionic liquids (TSILs) can be defined as liquid salts in which functional group is covalently tethered to the cation or anion (or both) of the salts. By incorporating a catalytic active group on the cation or anion, a new type of ionic liquid catalytic material could be obtained. Due to their novel physicochemical properties and facile separation and recycling, TSILs are regarded as powerful catalysts for a variety of important catalytic processes. The present review focuses on our recent progresses in the field of TSILs with particular emphasis on their applications in catalysis. The existing problems and the developing direction of the further research are also put forwarded.

Purification and biochemical characterization of soluble methane monooxygenase hydroxylase from Methylosinus trichosporium IMV 3011

Methane monooxygenase hydroxylase was purified by chromatography and characterized by electrophoresis and spectroscopy. The molecular mass of hydroxylase was 201.3 KDa as determined by gel filtration, whereas the total molecular mass was 234 KDa as judged by SDS–PAGE. Structure study indicated that the enzyme is a homodimer structure, consisting of three subunits, designated α, β, and γ, with molecular masses of 58 KDa, 36 KDa, and 23 KDa respectively. IEF analysis indicated that the enzyme has a pI of 5.2. The UV–Vis spectrum of hydroxylase revealed an absorption peak near 281 nm and a weak shoulder peak around 395 nm–420 nm, and a fluorescence spectrum revealed an emission peak at 341.3 nm. Circular dichroism measurement indicated that hydroxylase mainly consists of α-helical regions. Finally, phylogenetic analysis indicated that this strain is very close to Methylosinus trichosporium OB3b.

Recent progress in asymmetric epoxidation of olefins catalyzed by non-heme iron, manganese complexes

Optically active epoxides are regarded as important intermediates in organic reactions. Metallooxy-genases-catalyzed oxidations often exhibit high efficiency as well as selectivity, and operate under mild conditions through inherently green processes. Asymmetric epoxidation of olefins catalyzed by a series of iron or manganese complexes with chiral tetradentate nitrogen ligands to mimic non-heme iron dioxygenase has become an important method for obtaining chiral epoxides with high yields and high enantioselectivities. Recent progress in asymmetric epoxidation of olefins catalyzed by iron or manganese complexes with tetradentate nitrogen ligands and the corresponding mechanisms are described.

Effect of Alumina Support and Barium Oxide on the Structure and Catalytic Activity of Ruthenium Catalysts for Ammonia Synthesis

A series of Ba-Ru/Al2O3 catalysts were prepared by the impregnation method using industrial alumina (Al2O3-1) and synthesized alumina (Al2O3-2) as supports. The catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, X-ray fluorescence spectroscopy, transmission electron microscopy, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, and X-ray photoelectron spectroscopy. The effect of Al2O3 and the BaO promoter on the phase structure, texture properties, morphology, surface properties, and catalytic activity in ammonia synthesis were investigated. The results indicate that the physical and chemical properties of Al2O3 have a strong impact on the structure and activity of the ruthenium catalysts. The BaO promoter has a strong impact on the ruthenium catalyst in two ways: first, the amount of BaO added leads to a difference in the interaction between BaO and γ-Al2O3, which further influences the specific area and the porous structure of the catalysts; second, the addition of BaO influences the reduction process and the surface acidity and alkaline properties of the ruthenium catalysts. A proper amount of BaO promotes the activity and the optimal amount of BaO depends on the properties of the supports.