查看更多>>摘要：? 2022 Elsevier B.V.Ionic liquids are potential media/solvents for asymmetric synthesis when combined with chiral catalysts, while most reported catalysts are homogenous, making them difficult to separate from the reaction systems. Herein, chiral porous poly(ionic liquid)s (CPPILs) containing chiral salen Mn(III) complex have been successfully synthesized through a simple and one-pot route involving simultaneously occurred Friedel-Crafts alkylation and quaternization. These CPPILs possess large specific surface area, plentiful micro/meso-porosity, and abundant ionic active sites. Consequently, CPPILs can serve as highly efficient heterogeneous catalysts for asymmetric epoxidation of styrene. Excellent catalytic performance with yield of epoxides and enantiomeric excess value comparable with or even higher than that of the homogeneous system was achieved. The high catalytic activity can be further expanded to various substrates of unfunctionalized olefins. These catalysts are stable and could be recycled at least five times without significant loss of reactivity and enantioselectivity.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, entropy stabilized catalytic systems have been raised great concerns due to the urgent demand for functional materials aiming to realize chemical catalysis. As one of the significant groups, high entropy oxides (HEOs) with variable structure, controllable chemical composition, and rich functional properties have become the research hotspots. This review briefly introduces the advantages of HEOs in the catalytic system brought by their structural characteristics and fully summarizes recent applications of HEOs in thermal/electro/photo-catalysis and supports. Finally, the future prospects of HEOs in environmental catalysis, such as visible light catalysis, catalytic wet air oxidation (CWAO), and single-atom catalyst supports are proposed, which will provide a general direction for the development and breakthrough of HEOs in related fields.
查看更多>>摘要：? 2022 Elsevier B.V.This work reports main principles for designing metal/N-doped carbon (metal/NC) nanocatalysts via sol-gel method with high catalysis performances toward hydrogenation reduction reactions of 4-nitrophenol. Depending on standard electrode potentials of metallic ions, different kinds of polymerization agents should be selected. For designing Pd/NC, Pt/NC, Ni-Pd/NC nanocatalysts, starch can be selected as polymerization agent, and ethylene diamine tetraacetic acid is effective in designing Cu/NC nanocatalysts. For designing Ni/NC and Co/NC nanocatalysts, polyols, amines and amides, extracts of plant leaves can be used as polymerization agent. Nanocatalysts could be obtained when the dried precursors were calcined in the range of 350–700 °C under N2 atmosphere. By using NaBH4 as reducing agent, high activity parameter (per mass of metal) of 68.8 s?1·g?1, 597.1 s?1·g?1, 5571.7 s?1·g?1 can be obtained for Ni/NC, Cu/NC and Pd/NC nanocatalysts toward hydrogenation reaction of 4-nitrophenol. Our results provide new insight into designing and application of metal/N-doped carbon nanocatalysts.
查看更多>>摘要：? 2022 Elsevier B.V.The production of jet-fuel precursors from the aldol-dimerization of levulinic acid (LA) over acid zeolites is presented. Under solventless conditions, high LA conversion with selectivities to LA dimers > 90% are achieved. Chemisorption and spectroscopic analyses of the materials have revealed a cooperative effect between strong Br?nsted (BS) and strong Lewis (LS) acid sites, which favors the selective formation of dimers. BEA structure is the most efficient owing to shape selectivity effect. H-Beta 19, having an optimum Br?nsted to Lewis acid sites ratio and the adequate balance of BS/LS acid sites, displayed the best catalytic performance in terms of activity and selectivity to LA dimers. Under optimized reaction conditions H-Beta 19 achieved 79% LA conversion and > 98% selectivity. An analysis on the stability showed good reusability in consecutive reaction cycles. The small loss of activity, ascribed to the formation of organic deposits, can be reverted by calcination in air.
查看更多>>摘要：? 2022 Elsevier B.V.Currently, the catalytic hydrodeoxygenation (HDO) of oxygen-containing compounds derived from biomass to highly valuable chemicals or hydrocarbon bio-fuels is attracting more and more attention. Concerning the design and synthesis of high-performance supported metal catalysts for HDO, the efficient deposition/immobilization of active metal species on supports, as well as the construction of the favorable properties of supports, is quite necessary. In this work, we fabricated series of aluminum-zirconium oxide solid solution supported Ni-based catalysts by a simple surfactant-assisted homogeneous coprecipitation and applied them in the HDO of anisole. Various structural characterizations showed that surface-interface properties of Ni-based catalysts (i.e., surface acidity, defective structures, and metal-support interactions) could be finely tuned by adjusting the amount of Al introduced into Al-Zr oxide solid solutions, thus profoundly governing their catalytic HDO activities. It was demonstrated that the introduction of an appropriate amount of Al could not only enhance surface acidity and promote the formation of defective Zr-Ov-Al structures (Ov: oxygen vacancy) but also facilitate the generation of interfacial Niδ+ species bound to the support. Over the Ni-based catalyst bearing an Al2O3:ZrO2 mass ratio of 5:2, a high cyclohexane yield of ～77.4% was attained at 230 °C and 1.0 MPa initial hydrogen pressure. The high catalytic HDO efficiency was revealed to be correlated with the catalytic synergy between Ni0 and adjacent interfacial Niδ+ species, together with the promotion of neighboring defective oxygen vacancies and acidic sites, which contributed to the enhanced activation of the methoxy group in anisole and reaction intermediate and thus greatly improved HDO activity. The present findings offer a new and promising guidance for constructing high-performance metal-based catalysts via a rational surface-interface engineering.
查看更多>>摘要：? 2022 Elsevier B.V.Herein, we designed and prepared a novel two-dimensional/two-dimensional WS2/Bi2WO6 heterostructure photocatalyst. Firstly, by first-principles calculations, we found that Bi2WO6 and WS2 could form a stable WS2/Bi2WO6 heterostructure with a type-II band alignment structure. Supporting by the theoretical prediction, a series of WS2/Bi2WO6 heterostructures with different amounts of WS2 were synthesized via a facile hydrothermal method. The WS2/Bi2WO6 heterostructures exhibited higher photocatalytic activity in degradation of rhodamine B and oxytetracycline under visible light irradiation than the pure Bi2WO6 and WS2. And the WS2/Bi2WO6 heterostructure had a large specific surface area and good photo-stability. The photoluminescence spectra and photoelectrochemical measurements showed that the WS2/Bi2WO6 heterostructure possessed the ability to facilitate the separation and transfer of photo-generated carries. The active species generated in the photocatalytic system were photo-induced holes, singlet oxygen, and superoxide anion, which were verified by the trapping experiments and electron spin resonance technique. Furthermore, a Z-scheme photocatalytic mechanism was proposed.
查看更多>>摘要：? 2022 Elsevier B.V.A novelty catalyst synthesis method is introduced in this investigation, which employs O3 pulse to induce a segregation of Pd-Pt species to synthesize Pt-Pd core shell structural catalyst. In Pt-Pd alloy, O3 releases highly active oxygen (O*) species (O3→O2 + O·), which combine with Pd species or Pt species selectively. This combination induces a relative migration between Pd and Pt atoms, forming Pt-core@PdO-shell structural catalyst, which meets the thermodynamic stability of Pt-Pd alloy. Core shell structural catalyst displays a better catalytic performance for C-H bond activation. Experimental results indicate core-shell structural catalyst produces more highly active oxygen species than alloy catalyst does. These highly active oxygen species activate C-H bond in alkanes, contributing to a higher catalytic reactivity. In addition, the interaction between Pt-core and PdO-shell lowers the binding energy of ionic Pd species, which facilitates the release of reactive oxygen species.
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