Ning Zhang

3-Aminopropyl-triethoxysilane Functionalized Graphene Oxide: A Highly Efficient and Recyclable Catalyst for Knoevenagel Condensation

A solid base catalyst has been prepared by covalent functionalization of graphene oxide with 3-aminopropyl-triethoxysilane. The catalyst exhibits a superior catalytic performance in Knoevenagel condensation (over 90xa0% yield and at least seven times reusability), and is applicable to a wide range of substrates.Graphical Abstract

One-Pot Facile Fabrication of Multiple Nickel Nanoparticles Confined in Microporous Silica Giving a Multiple-Cores@Shell Structure as a Highly Efficient Catalyst for Methane Dry Reforming

Methane dry reforming (MDR) is a very important reaction, which can efficiently use two kinds of greenhouse gases (CO2 and CH4) to prepare synthesis gas or produce green hydrogen energy. What inhibits the industrialization of MDR is the sintering of active Ni nanoparticles and severe carbon deposition for Ni‐based catalysts. To resolve these problems, a novel structured catalyst with multiple ultra‐small Ni nanoparticles (4.3u2005nm) as the core and microporous silica as the shell was rationally fabricated by a facial one‐pot reverse micelle method and applied for MDR. The multiple‐cores@shell (M‐Ni@SiO2) catalyst displays superior carbon resistance and long‐term durability with the methane and carbon dioxide conversion close to thermodynamic equilibrium and a H2 to CO molar ratio near 1, whereas the commercial catalyst, Ni/Al2O3, and Ni directly supported on silica spheres (Ni/SiO2) show low stability and notable carbon deposition. The ultra‐small Ni particle size and confinement effect of the porous silica shell are believed to be the determining factors for the outstanding performance of the multiple‐cores@shell catalyst. The novel multiple‐cores@shell structure catalyst could be potentially used for industrial applications of MDR.

La-doped Pt/TiO2 as an efficient catalyst for room temperature oxidation of low concentration HCHO

Catalytic oxidation of formaldehyde (HCHO) is the most efficient way to purify indoor air of HCHO pollutant. This work investigated rare earth La-doped Pt/TiO 2 for low concentration HCHO oxida-tion at room temperature. La-doped Pt/TiO 2 had a dramatically promoted catalytic performance for HCHO oxidation. The reasons for the La promotion effect were investigated by N 2 adsorption, X-ray diffraction, CO chemisorption, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and high-angle annular dark field scanning TEM. The Pt nanoparticle size was reduced to 1.7 nm from 2.2 nm after modification by La, which led to higher Pt dispersion, more exposed active sites and enhanced metal-support interaction. Thus a superior activity for indoor low concentration HCHO oxidation was obtained. Moreover, the La-doped TiO 2 can be wash-coated on a cordierite monolith so that very low amounts of Pt (0.01 wt%) can be used. The catalyst was evaluated in a simulated indoor HCHO elimination environment and displayed high purifying efficiency and stabil-ity. It can be potentially used as a commercial catalyst for indoor HCHO elimination.

Elucidating the promotional effects of niobia on SnO2 for CO oxidation: developing an XRD extrapolation method to measure the lattice capacity of solid solutions

A series of Sn–Nb binary catalysts have been prepared by using a co-precipitation method and used for CO oxidation. All the catalysts show much higher specific surface areas than the individual oxides, indicating their improved thermal stability. It was found that Nb5+ cations can be doped into the lattice of tetragonal rutile SnO2 to replace a portion of the Sn4+ to form a solid solution structure. Using an XRD extrapolation method, the SnO2 lattice capacity for Nb2O5 has been quantified, which proves that only 25% of the Sn4+ in the SnO2 lattice can be replaced by Nb5+ to form a stable solid solution. For the samples with Nb contents below the capacity, the formed solid solution structure can induce the formation of a large quantity of stable and active surface deficient oxygen species due to charge imbalance and lattice defects, which improve the CO oxidation activity remarkably. For the samples with Nb contents above the capacity, the excess Nb is present as free Nb2O5 in the catalysts, which is harmful to their activity. It is concluded that Nb, as an effective promoter for SnO2, must be incorporated into its lattice as Nb5+ to form a solid solution. A Sn–Nb solid solution without excess Nb2O5 is not only a promising catalyst itself, but also a good support for precious metals to prepare catalysts for CO oxidation.

Pd-Metalated Conjugated Nanoporous Polycarbazoles for Additive-Free Cyanation of Aryl Halides: Boosting Catalytic Efficiency through Spatial Modulation

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. The catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

Mesoporous Y2Sn2O7 pyrochlore with exposed (111) facets: an active and stable catalyst for CO oxidation

Pyrochlore with an A2B2O7 crystal structure is a perfect mixed oxide for catalytic application for its high thermal stability. In the present manuscript, mesoporous Y2Sn2O7 pyrochlore with exposed (111) facets was successfully synthesized via a simple hydrothermal method and used for CO oxidation. In comparison with Y2Sn2O7 prepared by a co-precipitation method (Y2Sn2O7-CP), Y2Sn2O7 prepared by a hydrothermal method (Y2Sn2O7-HT) showed superior catalytic performance for CO oxidation. Even after calcination at 800 °C for 4 h (Y2Sn2O7-HT-800), its catalytic performance was still better than that of Y2Sn2O7-CP. Y2Sn2O7-HT is also a good support for Pd nanoparticles. Pd/Y2Sn2O7-HT demonstrates the best performance for CO oxidation among all the catalysts. All the samples were characterized by XRD, SEM, TEM, HAADF-STEM Mapping, N2 adsorption/desorption, H2-TPR, CO-TPD and Raman spectra to reveal their physicochemical properties. Compared with Y2Sn2O7-CP, Y2Sn2O7-HT has more exposed (111) facets, possesses a higher amount of active surface oxygen species and had high mesoporous surface areas, which should be the reasons accounting for the superior CO oxidation performance of Y2Sn2O7-HT and Pd/Y2Sn2O7-HT. Pd/Y2Sn2O7-HT also shows superior water-tolerance. In wet feed, its catalytic activity was even better than that in dry feed. Therefore, Pd/Y2Sn2O7-HT may be a potential catalyst for practical vehicle emission control.

Ni/Ln2Zr2O7 (Ln = La, Pr, Sm and Y) catalysts for methane steam reforming: the effects of A site replacement

A series of Ln2Zr2O7 supports (Ln = La, Pr, Sm and Y) with different “A” sites were prepared by a glycine–nitrate combustion method and used to support Ni to prepare catalysts for methane steam reforming for hydrogen production. It is revealed by XRD and Raman techniques that with the decrease of the rA/rB ratio in the sequence La, Pr, Sm and Y, the structures of the compounds become less ordered with the transformation of the bulk phase from ordered pyrochlore (La2Zr2O7) to less ordered pyrochlore (Pr2Zr2O7 and Sm2Zr2O7) and subsequently to defective fluorite (Y2Zr2O7). XPS demonstrated that the oxygen vacancies and mobility of the compounds also improve with the sequence. As supports for Ni, those possessing more mobile oxygen species display evidently enhanced coke resistance. In addition, as evidenced by H2-TPR, the supported Ni active sites have a stronger interaction with those supports having a higher degree of disorder, which improves both the Ni dispersion and the thermal stability of the prepared Ni/Ln2Zr2O7. Y2Zr2O7 support with a defective fluorite structure has the highest amount of mobile oxygen species. Therefore, the Ni active species has a stronger interaction with it than with the other three supports, which results in the smallest Ni grains with the highest metallic active surface area. As a consequence, Ni/Y2Zr2O7 exhibits the highest activity, stability and coke resistance among all of the catalysts. It is concluded that A site replacement by rare earth cations with different radii influences the structures of Ln2Zr2O7 significantly, which ultimately affects the reaction performance of the prepared Ni/Ln2Zr2O7 catalysts for methane steam reforming.

A Novel 3D Coordination Polymer Bearing Rare NbO-x-d Subnets: Synthesis, Structure, and Properties

Employing the multicarboxylate and N-donor mixed ligands to react with Zn(NO3)2·6H2O affords a new 3D compound [Zn3(HBPTC)2(bmp)2(H2O)2]·2H2O (1) (H4BPTCu2009=u2009biphenyl-3,3′,4,4′-tetracarboxylic acid, bmpu2009=u20093,6-bis(imidazol-1-yl)pyridazine). Structural analyses show that compound 1 possesses a (4,4)-connected neutral framework bearing rare NbO-x-d subnets, and it represents the first replica of the theoretically predicted NbO-x-d/Im-3m→Imm2 topology net. Moreover, compound 1 can demonstrate the interesting reversible structural transformation property induced by water molecules. Additionally, thermal stability and luminescence properties of 1 were investigated.

Mesoporous High-Surface-Area Copper-Tin Mixed-Oxide Nanorods: Remarkable for Carbon Monoxide Oxidation

Mesoporous, high‐surface‐area Cu–Sn mixed‐oxide nanorods were fabricated for the first time by nanocasting with the use of mesoporous KIT‐6 silica as the hard template. The Cu–Sn nanorods are significantly more active than 1u2009% Pd/SnO2 for the oxidation of CO and possesses long‐term durability and potent water resistance; they thus have the potential to replace noble metal catalysts for emission‐control processes.

Treating Copper(II) Oxide Nanoflowers with Hydrogen Peroxide: A Novel and Facile Strategy To Prepare High-Performance Copper(II) Oxide Nanosheets with Exposed (1 1 0) Facets

CuO nanosheets with exposed active (1u20091u20090) facets were facilely prepared through surface structure engineering by reassembling CuO nanoflowers in H2O2 aqueous solution. The CO oxidation activity on these CuO nanosheets was markedly higher than that on the pristine nanoflowers, for which the 100u2009% CO conversion temperature on the former was 40u2009°C lower than that on the latter and equal to that on a commercial catalyst (1u2009%Pd/γ‐Al2O3). This work provides a new strategy to design and prepare high‐performance nanostructured CuO catalysts.