Lanthanide (Eu3+, Tb3+) Centered Mesoporous Hybrids with 1,3‐Diphenyl‐1,3‐Propanepione Covalently Linking SBA‐15 (SBA‐16) and Poly(methylacrylic acid)

1,3‐Diphenyl‐1,3‐propanepione (DBM)‐functionalized SBA‐15 and SBA‐16 mesoporous hybrid materials (DBM‐SBA‐15 and DBM‐SBA‐16) are synthesized by co‐condensation of modified 1,3‐diphenyl‐1,3‐propanepione (DBM‐Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 and Pluronic F127 as a template, respectively. The as‐synthesized mesoporous hybrid material DBM‐SBA‐15 and DBM‐SBA‐16 are used as the first precursor, and the second precursor poly(methylacrylic acid) (PMAA) is synthesized through the addition polymerization reaction of the monomer methacrylic acid. These precursors then coordinate to lanthanide ions simultaneously, and the final mesoporous polymeric hybrid materials Ln(DBM‐SBA‐15)₃PMAA and Ln(DBM‐SBA‐16)₃PMAA (Ln=Eu, Tb) are obtained by a sol‐gel process. For comparison, binary lanthanide SBA‐15 and SBA‐16 mesoporous hybrid materials (denoted as Ln(DBM‐SBA‐15)₃ and Ln(DBM‐SBA‐16)₃) are also synthesized. The luminescence properties of these resulting materials are characterized in detail, and the results reveal that ternary lanthanide mesoporous polymeric hybrid materials present stronger luminescence intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary lanthanide mesoporous hybrid materials. This indicates that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system. In addition, the SBA‐15 mesoporous hybrids show an overall increase in luminescence lifetime and quantum efficiency compared with SBA‐16 mesoporous hybrids, indicating that SBA‐15 is a better host material for the lanthanide complex than mesoporous silica SBA‐16.     

Epoxidation of cyclohexene with H2O2 over efficient water‐tolerant heterogeneous catalysts composed of mono‐substituted phosphotungstic acid on co‐functionalized SBA‐15

A series of Keggin‐type heteropolyacid‐based heterogeneous catalysts (Co‐/Fe‐/Cu‐POM‐octyl‐NH₃‐SBA‐15) were synthesized via immobilized transition metal mono‐ substituted phosphotungstic acids (Co‐/Fe‐/Cu‐POM) on octyl‐amino‐co‐functionalized mesoporous silica SBA‐15 (octyl‐NH₂‐SBA‐15). Characterization results indicated that Co‐/Fe‐/Cu‐POM units were highly dispersed in mesochannels of SBA‐15, and both types of Brønsted and Lewis acid sites existed in Co‐/Fe‐/Cu‐POM‐octyl‐NH₃‐SBA‐15 catalysts. Co‐POM‐octyl‐NH₃‐SBA‐15 catalyst showed excellent catalytic performance in H₂O₂‐mediated cyclohexene epoxidation with 83.8% of cyclohexene conversion, 92.8% of cyclohexene oxide selectivity, and 98/2 of epoxidation/allylic oxidation selectivity. The order of catalytic activity was Co‐POM‐octyl‐NH₃‐SBA‐15 > Fe‐POM‐octyl‐NH₃‐SBA‐15 > Cu‐POM‐octyl‐NH₃‐SBA‐15. In order to obtain insights into the role of ‐octyl moieties during catalysis, an octyl‐free catalyst (Co‐POM‐NH₃‐SBA‐15) was also synthesized. In comparison with Co‐POM‐NH₃‐SBA‐15, Co‐POM‐octyl‐NH₃‐SBA‐15 showed enhanced catalytic properties (viz. activity and selectivity) in cyclohexene epoxidation. Strong chemical bonding between ‐NH₃⁺ anchored on the surface of SBA‐15 and heteropolyanions resulted in excellent stability of Co‐POM‐octyl‐NH₃‐SBA‐15 catalyst, and it could be reused six times without considerable loss of activity.     

Quantitative Raman and ESCA characterization of titania supported tungsten catalysts

Summary The distribution of supported species in a series of W/TiO₂ catalysts (1.8 – 28 wt% WO₃) has been determined by Raman and X-ray photoelectron spectroscopy (XPS, ESCA). The results show that three tungsten species are present on oxidic W/TiO₂ catalysts. A tungsten interaction species is formed almost exclusively for catalysts with W loadings lower or equal to 6.7 wt% WO₃. WO₃ is observed above 6.7 wt% WO₃. For W loadings higher than 10 wt%, a disordered W species W_DS is also present. The amounts of W_DS and WO₃ increase with increasing W content above 10 wt% WO₃.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

不同载体对负载型氧化钨催化剂在己二酸合成反应中的结构及性能影响

以SBA-15、六角介孔二氧化硅（HMS）和SnO₂为载体,通过浸渍法合成了含钨负载型催化剂,并考察了三种催化剂在环氧环己烷选择氧化制备己二酸反应中的催化性能. 通过X射线衍射（XRD）,透射电镜/场发射透射电镜（TEM/FETEM）,紫外-可见漫反射光谱（UV-Vis DRS）,拉曼（Raman）光谱,X射线光电子能谱（XPS）以及傅里叶变换红外（FTIR）光谱等手段对各种催化剂的结构进行表征. 结果表明,载体与催化剂的性能有密切的关系. 以SnO₂为载体的WO₃/SnO₂催化剂活性最高,其次是WO₃/HMS催化剂,WO₃/SBA-15 催化剂的活性最差.XRD 分析显示WO₃/SnO₂催化剂中氧化钨物种的晶化程度最低,TEM 和XPS 结果表明氧化钨物种在WO₃/SnO₂催化剂表面高度分散并且粒径尺寸很小（约2 nm）,UV-Vis DRS结果表明在WO₃/SnO₂催化剂中存在孤立[WO₄]四面体和低聚态的钨物种,这些物种的存在可能是WO₃/SnO₂催化剂具有高活性的主要原因. 此外,WO₃/SnO₂催化剂可以重复使用多次,6 次反应后己二酸（AA）得率仍然保持在80%以上,说明氧化钨物种与SnO₂载体间存在强烈的相互作用,从而提高了催化剂的稳定性.     

Dehydrogenation of Isobutane to Isobutene with Carbon Dioxide over SBA‐15‐Supported Chromia‐Ceria Catalysts

A series of SBA‐15‐supported chromia‐ceria catalysts with 3% Cr and 1%–5% Ce (3Cr‐Ce/SBA) were prepared using an incipient wetness impregnation method. The catalysts were characterized by XRD, N₂ adsorption, SEM, TEM‐EDX, Raman spectroscopy, UV–vis spectroscopy, XPS and H₂‐TPR, and their catalytic performance for isobutane dehydrogenation with CO₂ was tested. The addition of ceria to SBA‐15‐supported chromia improves the dispersion of chromium species. 3Cr‐Ce/SBA catalysts are more active than SBA‐15‐supported chromia (3Cr/SBA), which is due to a higher concentration of Cr⁶⁺ species present on the former catalysts. The 3Cr‐3Ce/SBA catalyst shows the highest activity, which gives 35.4% isobutane conversion and 89.6% isobutene selectivity at 570 °C after 10 min of the reaction.     

Influence of Pore Structure on Catalytic Properties of Mesoporous Silica-supported Co-B Amorphous Alloys in Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol

Co‐B amorphous alloy catalysts supported on three kinds of mesoporous silica (common SiO₂, MCM‐41 and SBA‐15) have been systematically studied focusing on the effect of pore structure on the catalytic properties in liquid‐phase hydrogenation of cinnamaldehyde to cinnamyl alcohol (CMO). Structural characterization of a series of different catalysts was performed by means of N₂ adsorption, X‐ray diffraction, transmission electron microscopy, hydrogen chemisorption, and X‐ray photoelectron spectroscopy. Various characterizations revealed that the pore structure of supports profoundly influenced the particle size, location and dispersion degree of Co‐B amorphous alloys. Co‐B/SBA‐15 was found more active and selective to CMO than either Co‐B/SiO₂ or Co‐B/MCM‐41. The superior catalytic activity could be attributed to the higher active surface area, because most of Co‐B nanoparticles in Co‐B/SBA‐15 were located in the ordered pore channels of SBA‐15 rather than on the external surface as found in Co‐B/SiO₂ and Co‐B/MCM‐41. Meanwhile, the geometrical confinement effect of the ordered mesoporous structure of SBA‐15 was considered to be responsible for the enhanced selectivity to CMO on Co‐B/SBA‐15, inhibiting the further hydrogenation of CMO to hydrocinnamyl alcohol.     

Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica

Immobilized nickel catalysts SBA*‐ L ‐x/Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N₃‐x. Related homogeneous ligand LtBu and its Ni^II complexes, [Ni( LtBu )(OAc)₂(H₂O)] ( LtBu /Ni) and [Ni( LtBu )₂]BF₄ (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐x/Ni suggests the formation of an inert [Ni L ₂] site on the surface at higher ligand loadings. SBA*‐ L ‐x/Ni has been applied to the catalytic oxidation of cyclohexane with m‐chloroperbenzoic acid (mCPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.     

WxC/SBA-16催化剂的制备、表征及催化加氢脱硫性能

以正硅酸乙酯为硅源, 仲钨酸铵为钨源, P123和F127为混合模板剂,采用水热晶化法一步合成了不同钨含量(以n(Si):n(W)表示)的WO3/SBA-16, 然后经甲烷/氢气(V(CH4)/V(H2)=1/4)混和气体程序升温还原碳化(TPC), 制备出了WxC/SBA-16(x=1, 2)催化剂. 采用XRD、N2-吸附/脱附、TEM和FTIR等分析测试技术对样品的结构进行了表征, 并以噻吩作为模型化合物, 对WxC/SBA-16催化剂的加氢脱硫催化活性进行了评价. 结果表明, 在一定钨含量的条件下, WO3/SBA-16和WxC/SBA-16样品仍然保持立方笼状介孔结构, 当n(Si):n(W)为30-10时, 碳化钨的物相为W2C; n(Si):n(W)为7.5时, 碳化钨的物相为W2C和WC. WxC/SBA-16催化剂表现出了良好的加氢脱硫催化性能.     

Effect of tungsten oxide loading on metathesis activity of ethene and 2-butene over WO<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> catalysts

The metathesis of ethene and 2-butene to propene was studied over WO₃/SiO₂ catalysts with various WO₃ loadings (2, 4, 8, 12, 16, and 24 wt%). The 2-butene conversion and propene selectivity increased greatly with WO₃ loading increasing from 2 to 8 wt%, reached maximum at 8–12 wt% WO₃ loading, and then decreased when the WO₃ loading was higher than 12 wt%. From the above results and taking the economics into account, the optimal amount of WO₃ loading was ~8 wt%. The catalysts were characterized by physico-chemical and spectroscopic techniques to elucidate the effect of different tungsten oxide loadings on the metathesis reactivity of ethene and 2-butene. The characterization data indicated that three types of tungsten species (i.e., surface tetrahedral tungsten species, surface octahedral polytungstate species, and WO₃ crystallites) were present in the catalysts. It was found that WO₃ was not the active centers, and surface tetrahedral tungsten species might be more active than octahedral polytungstate species in metathesis reaction. The reduced form of tungsten species [W⁺⁴, W⁺⁵, and W^+(6−y) (0 < y < 1)] may be the suitable state of W species acting as metathesis active centers.     

Molybdenum‐ and Tungsten‐Based Coordination Polymers as Catalysts for an Efficient and Rapid Synthesis of Hexahydro‐5‐oxoquinoline‐3‐carboxylates and 1,4‐Dihydropyridine‐3,5‐dicarboxylates

Hexahydro‐5‐oxoquinoline‐3‐carboxylates and 1,4‐dihydropyridine‐3,5‐dicarboxylates were synthesized efficiently and rapidly (2 min) in the presence of molybdenum‐ and tungsten‐based coordination polymers [M(Bu₃Sn)₂O₄)]_n (M=Mo or W) as catalysts (Schemes 1 and 2; Tables 2 and 3). The products were formed at room temperature in excellent yields (90–98%). The catalysts worked under heterogeneous conditions and were recyclable. The earlier reports for the application of these polymers to conduct organic synthesis are limited. The present method explores a new and useful application of these catalysts.     

常温常压下硅氨基化介孔SBA-15负载Keggin型钼钒杂多酸催化氧化乙醛的反应研究

Keggin-type molybdovanadophosphoric acids(HPA),H_4PMo_(11)VO_(40)(1),H_5PMo_(10)V_2O_(40)(2)and H_6PMo_9V_3O_(40)(3)were anchored onto γ-aminopropyltriethoxysilane(APTS)aminosilylated silica mesoporous SBA-15 throughacid-base neutralization and the resulting HPA/APTS/SBA-15 were characterized by BET,TEM,XRD,ICP,FTIRand ~(31)P MAS NMR.The characterization results indicate that the Keggin-structure of these HPAs is preservedwithin the mesoporous silica host.The samples were tested for catalytic aerobic oxidation of acetaldehyde hetero-geneously in liquid phase under ambient condition.The electrostatic force between heteropoly acid and aminogroups grafted on the silica channel surface leads to strong immobilization of HPA inside SBA-15 which is againstthe leaching during the reaction.The good catalytic performance and easy recycle of these catalysts make them aspotential environmental friendly catalysts for elimination of indoor air pollutants.     

Metathesis of butene to propene on WO<Subscript>3</Subscript> supported on MTS-9 titanium-silica: effect of loading on selectivity of product and yield of propene

An advanced heterogeneous catalyst for olefin disproportion was prepared by supporting WO₃ on titanium-silica sieve (MTS-9). The nature of the surface tungsten oxide species present in these catalysts was determined as a function of tungsten oxide loading by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectra (UV–DRS) and ultraviolet–visible Raman (UV-Raman). The catalyst showed high activity for the metathesis of butene to propene. The active centers are not crystallites of WO₃ but rather surface tungsten oxide species. The conversion of butene varies with the degree of catalyst loading.     

Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion‐Limited Atomic Layer Deposition

The heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion‐limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub‐nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA‐15, SBA‐16, and MCM‐41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD‐assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Tungstate supported mesoporous silica SBA‐15 with imidazolium framework as a hybrid nanocatalyst for selective oxidation of sulfides in the presence of hydrogen peroxide

In this work, a new heterogeneous catalyst (SBA‐15/Im/WO₄^2?) was prepared, and then its performance in the oxidation of organic sulfides was studied (using 30% H₂O₂ as green oxidant under neutral reaction conditions). This organic–inorganic hybrid mesoporous material was characterized by various techniques, such as FT‐IR, inductively coupled plasma, X‐ray powder diffraction, high‐resolution‐transmission electron microscopy, N₂ adsorption–desorption and thermogravimetric analysis. The catalyst was also applied to the selective oxidation of various sulfides. The hybrid catalyst was easily recovered, and was very stable and retained good activity for at least five successive runs without any additional activation. Moreover, there was no remarkable decrease in the activity and selectivity of the catalyst. The products could be easily isolated by just removing the solvent after filtering the catalyst. The yields of the catalytic productions through this catalyst were in the range from 75% to 97%.     

Pd(OAc)2@SBA‐15/PrEn nanoreactor: a highly active,reusable and selective phosphine‐free catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous media

A series of ordered mesoporous organic–inorganic hybrid material was designed by using the amine‐functionalized SBA‐15 (PdX₂@SBA‐15/N_Y, Y = 1, 2) as solid support for palladium complexes. Among them, the Pd(OAc)₂/ethylenediamine complex encapsulated into SBA‐15 (Pd(OAc)₂@SBA‐15/PrEn or Pd(OAc)₂@SBA‐15/PrNHEtNH₂) exhibits higher activity and selectivity toward Suzuki cross‐coupling reaction under aerobic conditions and water solvent mixture. The SBA‐15/PrEn supported palladium pre‐catalyst could be separated easily from reaction products and used repetitively several times, showing its superiority over homogeneous catalysts for industrial and chemical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

A Cheap and Efficient Methodology for the Solvent‐Free,One‐pot and Multi‐component Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalyzed by Mesoporous NH4H2PO4/MCM‐48 and Comparison of Its Catalytic Efficacy with NH4H2PO4/MCM‐41

The catalytic efficiency of ammonium dihydrogenphosphate was evaluated in the two heterogeneous forms of NH₄H₂PO₄/MCM‐48 and NH₄H₂PO₄/MCM‐41, as mesoporous catalysts, in the solvent free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones through one‐pot three‐component condensation of ethyl acetoacetate, an aryl aldehyde and urea. Different reaction parameters including catalytic efficacy, solvent effect, and urea concentration are considered.     

Ordered mesoporous SBA‐15/PrSO3Pd and SBA‐15/PrSO3PdNP as active,reusable and selective phosphine‐free catalysts in CX activation Heck coupling process

The incorporation of sulfonate into mesoporous SBA‐15 molecular sieves as ligands for palladium ions was used. Then SBA‐15/PrSO₃Pd and SBA‐15/PrSO₃Pd_NP were prepared and applied for the Heck arylation reaction of conjugate alkenes with aryl halides, to afford corresponding cross‐coupling products under phosphine‐free aerobic conditions with good to excellent yields. These supported palladium pre‐catalysts could be separated easily from reaction products and reused several times, showing superiority over homogeneous catalysts for industrial and chemical applications. Copyright © 2015 John Wiley & Sons, Ltd.     

铂-氢钨青铜电极的制备及对氢氧化的电催化

采用电化学还原法在表面改性的碳布上,通过改变催化剂沉积顺序及氢钨青铜沉积时间制备铂-氢钨青铜复合催化剂,所得电极作为质子交换膜燃料电池(PEMFC)阳极。利用X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、循环伏安(CV)及单电池极化性能测试研究了催化剂的组成、沉积量、分散性及其对氢氧化的电催化活性。实验结果表明,氢钨青铜沉积时间及催化剂沉积顺序对电极催化性能有显著影响,当氢钨青铜沉积时间为10 min,先沉积氢钨青铜、后沉积铂所得Pt/HxWO3电极对氢氧化具有最佳的催化活性。适量的氢钨青铜才能与铂形成较好的协同催化效应。     

Periodic mesoporous silica‐supported Ni(II) organometallic complex as an active and reusable nanocatalyst for water‐medium Sonogashira coupling reaction

Phenyl‐bridged periodic mesoporous organosilicas (PMOs) functionalized with diphenylphosphino (PPh₂‐) ligands were synthesized via a surfactant‐directed self‐assembly approach, and were used as a support to immobilize Ni(II) organometallic complex by coordination interaction. In comparison with Ni‐PPh₂‐SBA‐15 and Ni‐PPh₂‐PMOs(Et) catalysts, the as‐prepared Ni‐PPh₂‐PMOs(Ph) exhibited superior catalytic reactivity and selectivity in water‐medium Sonogashira reaction. A control experiment demonstrated that its high activity could be attributed to the high dispersion of Ni(II) active sites and ordered mesopore channels, which effectively diminished diffusion limitation. Meanwhile, the phenyl organic groups in the support wall enhanced surface hydrophobicity, which promoted the adsorption for organic reactant molecules. Moreover, it displayed almost the same catalytic efficiency with the corresponding homogeneous Ni(PPh₃)₂Cl₂ catalyst and could be used repetitively, which was considered as a more environmentally friendly catalytic process since it simultaneously avoided the use of noble metal active species and toxic organic solvents. Copyright © 2013 John Wiley & Sons, Ltd.