Tuning Interfacial Cu‐O Atomic Structures for Enhanced Catalytic Applications

Cu₂O/CuO_x (x=0, 1) nanocomposites with well‐defined morphologies have been widely applied in catalytic reactions. However, people still understand less about tuning interfacial Cu‐O atomic structures for enhanced catalytic applications, and a special review on this topic has not been reported so far. Herein, we summarize our understanding on tuning interfacial Cu‐O atomic structures based on the literature, including the formation as well as evolution mechanism of Cu‐O interfaces in Cu₂O/CuO and Cu₂O/Cu systems, and the improved performances in the fields of CO oxidation, NO_x oxidation, photoelectrocatalysis, water gas shift reaction, photodegradation of organic dyes, hydrogen evolution, and photoreduction of CO₂. Finally, we briefly propose several potential research directions.     

Deactivation of Cu‐Exchanged Automotive‐Emission NH3‐SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X‐ray Microscopy

To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NO_x with an ammonia reductant, we employed scanning transmission X‐ray microscopy (STXM) to study Cu‐exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000‐mile aging. X‐ray absorption near‐edge structure (XANES) measurements were performed at the Al K‐ and Cu L‐edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi‐factor‐induced catalytic deactivation. In Cu‐exchanged MFI, a transformation of Cu^II to Cu^I and Cu_xO_y was observed. We also found a spatial correlation between extra‐framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of Cu^I and tri‐coordinated Al. By inspecting both Al and Cu in fresh and aged Cu‐exchanged zeolites, we conclude that the importance of the preservation of isolated Cu^II sites trumps that of Brønsted acid sites for NH₃‐SCR activity.     

VOCs and carbonaceous particles removal assisted by NOx on alkali0.15/ZrO2 and Csx–M0.1/ZrO2 catalysts (M = Cu or Co)

The effect of alkali metals on the physicochemical characteristics of zirconium oxide and the properties of alkali metals in the oxidation of toluene and/or carbonaceous particles and/or conversion of nitrogen oxides have been studied. We observed that they had an effect on the structural and textural properties of ZrO₂. These solids were tested first in the oxidation of toluene and carbonaceous particles separately and secondly with both pollutants. Whatever the experiments, the sample Cs_0.15/ZrO₂ was found to be the catalyst the most active. The simultaneous removal of toluene and soot shows that the presence of toluene leads to a decrease in the temperature of the maximum soot oxidation rate, particularly with catalysts impregnated of Cs and Cu. The effect of the Cs/Co ratio on NO_x conversion and toluene oxidation was also studied. It was found that the oxidizing properties of NO_x can increase the conversion of toluene. This phenomenon occurs especially in the presence of catalysts with a low amount of alkali metal. For the oxidation of carbonaceous particles on the samples Cs/ZrO₂ impregnated with transition metals, the best performance is obtained for copper, although a decrease of the ratio Cs/Cu leads to a slower oxidation and a shift to higher temperatures.     

Effect of copper precursors on the catalytic activity of Cu/ZSM-5 catalysts for selective catalytic reduction of NO by NH<Subscript>3</Subscript>

The Cu/ZSM-5 catalysts prepared by different copper precursors were used for the selective catalytic reduction (SCR) of NO _x with NH₃. The Cu/ZSM-5 catalyst prepared by the copper nitrate (Cu/ZSM-5-N) presented the best performance among the Cu/ZSM-5 catalysts and showed above 90 % NO _x conversion at 225–405 °C. The average particle size of CuO was 5.82, 9.20, and 11.01 nm over Cu/ZSM-5-N, Cu/ZSM-5-S (prepared by copper sulfate), and Cu/ZSM-5-C (prepared by copper chloride), respectively. The Cu/ZSM-5-N catalyst showed the highly dispersed copper species, the strong surface acidity, and the excellent redox ability compared with the Cu/ZSM-5-C and Cu/ZSM-5-S catalysts. The Cu⁺ and Cu²⁺ existed in the Cu/ZSM-5 catalysts and the abundant Cu⁺ over Cu/ZSM-5-N might be responsible for the superior SCR activity.     

Time‐Resolved,In Situ DRIFTS/EDE/MS Studies on Alumina‐Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions

The effects of ceria and zirconia on the structure–function properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ‐Al₂O₃) during CO exposure are described. Ceria and zirconia are introduced through two preparation methods: 1) ceria is deposited on γ‐Al₂O₃ from [Ce(acac)₃] and rhodium metal is subsequently added, and 2) through the controlled surface modification (CSM) technique, which involves the decomposition of [M(acac)_x] (M=Ce, x=3; M=Zr, x=4) on Rh/γ‐Al₂O₃. The structure–function correlations of ceria and/or zirconia‐doped rhodium catalysts are investigated by diffuse reflectance infrared Fourier‐transform spectroscopy/energy‐dispersive extended X‐ray absorption spectroscopy/mass spectrometry (DRIFTS/EDE/MS) under time‐resolved, in situ conditions. CeO_x and ZrO₂ facilitate the protection of Rh particles against extensive oxidation in air and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts prepared by CSM are observed and compared with Rh/γ‐Al₂O₃ samples, whereas supported Rh particles are easily disrupted by CO forming mononuclear Rh geminal dicarbonyl species. DRIFTS results indicate that, through the interaction of CO with ceriated Rh particles, a significantly larger amount of linear CO species form; this suggests the predominance of a metallic Rh phase.     

Development of PGM-free catalysts for automotive applications

The activity of Ag-based catalysts in soot oxidation using NO₂ and oxygen as oxidants has been characterized in laboratory tests (TGA) and under real conditions on an engine dynamometer. Under low-temperature NO₂-assisted and high-temperature O₂-assisted soot oxidation conditions, the activity of Ag-based catalysts was found to be comparable or higher than that of commercial Pt-catalysts. In addition, Ag-based compositions also revealed noticeable NO _x storage, some passive NO _x reduction ability, and activity in NO oxidation. Ag-catalysts characterized in the present paper may be promising for the retrofit applications and high-temperature periodical regenerations with air for diesel passenger cars.     

Silicotungstic acid modified Ce‐Fe‐Ox catalyst for selective catalytic reduction of NOx with NH3: Effect of the amount of HSiW

The HSiW(x)/Ce‐Fe catalysts were used to research the effect of silicotungstic acid contents on the catalytic activity in the selective catalytic reduction of NO_x with NH₃. Doping different contents of silicotungstic acid affected surface species and redox property as well as the catalytic activity. With the increasing amount of HSiW (x = 5%, 10% and 20%), the redox reaction between Fe³⁺/Fe²⁺ and Ce⁴⁺/Ce³⁺ enhanced, which could improve the ratio of Ce³⁺ and Fe³⁺. And then, more Ce³⁺ increased the ratio of chemisorbed oxygen (O_α). Besides, the type and strength of acid sites over HSiW(_x)/Ce‐Fe was affected by the HSiW contents. These factors facilitated the catalytic performance. Thus, the NO_x conversion of HSiW(x)/Ce‐Fe(x = 20%) was higher than 90%, which maintained in a wide temperature range between 200 and 400 °C.     

三维有序大孔SnO2基固溶体用于有效燃烧碳烟颗粒

柴油车尾气排放的碳烟颗粒对人类的生存环境和身体健康带来了严重危害.催化燃烧是消除碳烟颗粒污染的有效途径.碳烟颗粒催化燃烧是固-固-气相反应,因此催化剂本身具有活泼的氧中心且其能与碳烟颗粒有效接触是提高反应效率的关键因素.为改善碳烟颗粒与催化剂的接触,设计制备三维有序大孔(3DOM)催化剂,使碳烟颗粒可以进入催化剂孔道内部,增加其与催化剂的有效接触,是提高反应活性的有效途径.此外,在催化剂晶格中掺杂其它金属离子形成固溶体结构,可提高其氧化还原性能,也可有效提高其碳烟燃烧活性.SnO2富含活泼的表面缺位氧和可还原的晶格氧,且其熔点高达1630 oC,具有良好的热稳定性,被广泛用于制备气体传感、电化学和催化等材料.在过去的6年中,本课题组在SnO2催化化学领域做了大量系统的工作,将SnO2基催化材料用于多种环保和能源反应.发现通过其它阳离子Fe3+,Cr3+,Ta5+,Ce4+和Nb5+等的掺杂,替换晶格中部分Sn4+形成金红石型SnO2固溶体结构,可显著提高催化剂氧物种的流动性、活性和本身的热稳定性.本文采用胶体晶体模板法制备出了Ce4+,Mn3+和Cu2+离子掺杂的SnO2三维有序大孔固溶体催化剂用于松散接触条件下的碳烟催化燃烧.采用SEM,TEM,XRD,STEM-mapping,O2-TPD和XPS等手段对催化剂进行表征,研究其碳烟催化燃烧性能.SEM和TEM结果表明已成功合成三维有序大孔结构样品.XRD,Raman和STEM-mapping结果表明,Ce4+,Mn3+和Cu2+离子均进入四方金红石型SnO2晶格形成固溶体结构.另外,Raman,H2-TPR,XPS和O2-TPD等结果发现上述离子掺杂三维大孔SnO2后,催化剂表面形成了更活泼、丰富的氧物种,有利于碳烟颗粒燃烧.其中3DOM-Cu1Sn9催化剂具有最丰富的活泼氧中心,因此表现出最高的活性.     

CeO2纳米层对多层载体x-CeO2/3DOM Al2O3负载纳米Au催化剂催化柴油炭烟燃烧活性的影响

与汽油车相比,柴油车具有CO2排放低、寿命长和经济性好等优点,所以近年来受到广泛关注并被大量使用.但是,柴油车在使用过程中会产生大量炭烟颗粒物(PM),对大气环境和人类健康造成很大威胁.因此,开展这方面的基础研究具有重要的科学意义及环境保护意义.催化柴油炭烟燃烧反应是一个气-固-固多相深度氧化反应,由于PM的粒径远大于传统催化剂,导致PM不能进入催化剂孔道内部,造成催化剂活性比表面积利用率较低.设计并制备大孔径的三维有序大孔结构(3DOM)的催化剂,能够减小反应扩散阻力,增加催化剂与炭烟颗粒物的有效接触,加快反应进行.另外,可以通过在3DOM氧化物表面担载其它活性组分,提高催化剂的氧化还原性能,进而提高其活性.CeO2有很好的储放氧性能,在柴油车尾气净化催化剂中较为常见,但是单一的CeO2热稳定性较差,高温下容易烧结,使得比表面积减小,并且失去储氧能力,造成催化剂失活.文献中较常见的解决办法是在CeO2中掺杂其它阳离子,如Zr4+,Pr3+,Al3+,La3+及Y3+等离子,以提高CeO2的抗高温烧结能力.此外,研究报道的催化剂对催化柴油炭烟颗粒物燃烧的峰值温度已经远低于炭烟颗粒物的自燃温度,但是对颗粒物的起燃温度仍普遍较高.我们前期研究结果表明,担载纳米Au颗粒催化剂能够显著降低炭烟燃烧的起燃温度.本文采用胶体晶体模板法制备了3DOM Al2O3载体,利用微孔膜-氨沉淀法担载不同量的活性组分CeO2,制备出一种负载型x-CeO2/3DOM Al2O3催化剂,它既可减少稀土元素用量,降低成本,又因为Al2O3的机械强度较高,还能保证催化剂的机械强度足够好.为了进一步降低催化剂催化炭烟燃烧的起燃温度,利用还原沉积法在多层载体x-CeO2/3DOM Al2O3上负载纳米Au催化剂,制备出不同厚度的CeO2纳米层负载Au催化剂(Au/x-CeO2/3DOM Al2O3).利用X射线衍射、扫描电镜、透射电镜、H2程序升温还原和O2程序升温脱附等方法研究了催化剂的结构及物化性质与催化剂活性之间的关系,提出了消除PM反应的可能机理.结果表明,Al3+离子能够部分进入到CeO2中,形成Al-Ce固溶体.由于Al离子半径小于Ce离子,Al3+掺杂后能引起CeO2晶格发生畸变,产生大量缺陷,形成大量氧空位,促进晶格氧的移动,从而使催化剂具有更大的储放氧能力.在Au/x-CeO2/3DOM Al2O3催化剂中,CeO2担载量过高时,氧化铈纳米层较厚,活性组分容易烧结,不利于催化剂活性提高;而CeO2担载量过低,则CeO2纳米层较稀薄,催化剂的氧化还原性能受限,催化剂活性也不高.因此,CeO2的担载量应适当.此外,Au和CeO2之间的强相互作用能够增加Au纳米颗粒表面活性氧物种的数量,从而促进柴油炭烟燃烧反应.活性测试结果表明,担载纳米Au颗粒后,催化剂催化柴油炭烟燃烧的起燃温度均明显降低,在所制备的系列催化剂中Au/20％CeO2/3DOM Al2O3催化剂展示了最高的催化活性,T10,T50和T90分别为267,372和426 oC.     

Structural Effects of Cu/Zn Substitution in the Malachite–Rosasite System

Synthetic zincian malachite samples (Cu_1–xZn_x)₂(OH)₂CO₃ with x = 0, 0.1, 0.2 and 0.3 were characterized by powder X‐ray diffraction and optical spectroscopy. The XRD patterns of the samples up to x = 0.2 indicate single phase materials with an approximately linear dependence of the refined lattice parameters on the zinc content. In contrast, the sample with a nominal zinc content x = 0.3 shows the formation of a small amount of aurichalcite (Zn,Cu)₅(OH)₆(CO₃)₂ as an additional phase. Based on the lattice parameter variations, the zinc content of the zincian malachite component in this sample is estimated to be x ≈? 0.27, which seems to represent the maximum possible substitution in zincian malachite under the synthesis conditions applied. The results are discussed in relation to preparation of Cu/ZnO catalysts and the crystal structures of the minerals malachite and rosasite. One striking difference between these two structurally closely related phases is the orientation of the Jahn–Teller elongated axes of the CuO₆ octahedra in the unit cell, which seems to be correlated with the placement of the monoclinic β angle. The structural and chemical relationship between these crystallographically distinct phases is discussed using a hypothetical intermediate Zn₂(OH)₂CO₃ phase of higher orthorhombic symmetry. In addition to the crystallographic analysis, optical spectroscopy proves to be a useful tool for estimation of the Cu:Zn ratio in (Cu_1–xZn_x)₂(OH)₂CO₃ samples.     

钾掺杂三维有序大孔结构Mn0.5Ce0.5Oδ催化剂合成及其催化燃烧炭烟性能

柴油发动机是一种高效耐用的发动机,具有广阔的应用前景.但柴油车尾气中的炭烟颗粒吸附了许多有毒有害物质,也是城市PM2.5的主要来源之一,对人类生命安全造成极大威胁.因此,降低和消除柴油车尾气中的炭烟颗粒是柴油车尾气净化的重要任务.尾气后处理是炭烟颗粒进入大气环境前的最后一道程序,可有效控制柴油车尾气中炭烟颗粒排放.其中,催化净化催化剂是尾气后处理技术的核心.研究表明,炭烟颗粒催化燃烧是一个气-固-固三相深度氧化反应,因此开发新型催化剂体系,改善催化剂与炭烟颗粒的接触,提高催化剂的本征活性,对于研制高活性炭烟燃烧催化剂具有重要的实际意义. 对于三维有序大孔(3DOM)结构催化剂,大孔有利于炭烟颗粒进入催化剂内部并与活性位点接触,而有序的孔道结构可以促进炭烟颗粒在催化剂孔道内传输.因此,将催化炭烟颗粒燃烧催化剂设计成3DOM结构,可促进炭烟颗粒催化燃烧,提高催化剂活性.研究表明,锰铈复合氧化物材料在炭烟颗粒催化燃烧中表现出比单一的锰氧化物和铈氧化物更好的性能.而将K与Ce和Mn形成复合氧化物,利用三者之间的协同作用,将可使K掺杂3DOM结构Mn0.5Ce0.5Oδ催化剂具有更高的催化活性.本文利用胶体晶体模板法成功制备了3DOM结构的Mn0.5Ce0.5Oδ复合氧化物,并采用简单的等体积浸渍方法成功制备了不同K担载量的K掺杂3DOM结构Mn0.5Ce0.5Oδ催化剂(K-MCO).表征结果表明, K-MCO催化剂具有贯通有序的大孔结构,但焙烧温度和焙烧时间会对大孔结构的规整性有一定影响;催化剂中K含量、焙烧温度和焙烧时间对K-MCO的晶型影响较大,催化剂中出现了一个新的晶相K2Mn4O8.另外, K含量、焙烧温度和焙烧时间对催化剂的氧化还原性能也有较大影响.评价结果表明,所制催化剂对炭烟催化燃烧均具有较高活性,其中20% K-MCO-4h催化剂活性最高,催化燃烧炭烟的T50(炭烟的最大燃烧峰值)为331oC, CO2选择性为95.3%.催化剂的大孔结构效应以及K, Mn和Ce三者间的协同作用有利于提高催化剂催化燃烧炭烟的活性.另外,由于柴油车尾气排气口温度范围为175–400 oC,而本文所制催化剂催化燃烧炭烟的温度低于400 oC,因此该催化剂可以在柴油车尾气排气口温度范围内进行炭烟催化燃烧.由于具有合成步骤简单、活性高以及成本低等优点,该催化剂在实际应用方面具有广阔前景.     

Structural Characterization of Alumina‐Supported Rh Catalysts: Effects of Ceriation and Zirconiation by using Metal–Organic Precursors

The effects of the addition of ceria and zirconia on the structural properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ‐Al₂O₃) are studied. Ceria and zirconia are deposited by using two preparation methods. Method I involves the deposition of ceria on γ‐Al₂O₃ from Ce(acac)₃, and the rhodium metal is subsequently added, whereas method II is based on a controlled surface reaction technique, that is, the decomposition of metal–organic M(acac)_x (in which M=Ce, x=3 and M=Zr, x=4) on Rh/γ‐Al₂O₃. The structures of the prepared catalyst materials are characterized ex situ by using N₂ physisorption, transmission electron microscopy, high‐angle annular dark‐field scanning transmission election microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy (XPS), and X‐ray absorption fine structure spectroscopy (XAFS). All supported rhodium systems readily oxidize in air at room temperature. By using ceriated and zirconiated precursors, a larger rhodium‐based metallic core fraction is obtained in comparison to the undoped rhodium catalysts, suggesting that ceria and zirconia protect the rhodium particles against extensive oxidation. XPS results indicate that after the calcination and reduction treatments, a small amount of chlorine is retained on the support of all rhodium catalysts. EXAFS analysis shows significant Rh? Cl interactions for Rh/Al₂O₃ and Rh/CeO_x/Al₂O₃ (method I) catalysts. After reaction with H₂/He in situ, for series of samples with 1.6 wt % Rh, the EXAFS first shell analysis affords a mean size of approximately 30 atoms. A broader spread is evident with a 4 wt % rhodium loading (ca. 30–110 atoms), with the incorporation of zirconium providing the largest particle sizes.     

Facile Fabrication of Ce/V‐Modified Multi‐Channel TiO2 Nanotubes and Their Enhanced Selective Catalytic Reduction Performance

To optimize one‐dimensional (1D) TiO₂ nanofibers, tailor‐made multi‐channel TiO₂ nanotubes have been successfully fabricated by electrospinning technology. After loading with Ce and V, the CeVTi‐tube catalyst exhibited a broad working temperature window and acceptable resistance to H₂O and SO₂ for elimination of NO_x. The corresponding analysis revealed that the multi‐channel structure provided more surface adsorbed oxygen species and that the wall of nanotubes anchored active components efficiently, which was beneficial to improve the stability as well as dispersion of the active components. Besides, a synergistic effect between Ce and V easily occurred at the CeVTi‐tube catalyst, and its reducibility was significantly improved since the electron transformation between Ce and V was dramatically enhanced. Consequently, the tailor‐made multi‐channel CeVTi‐tube catalyst exhibited satisfied de‐NO_x efficiency at the temperature range of 220–460 °C. It seemed that the multi‐channel TiO₂ nanotubes hold great potential as an excellent carrier for SCR catalysts.     

Furfural Hydrogenation on Nickel‐promoted Cu‐containing Catalysts Prepared from Hydrotalcite‐Like Precursors

The nickel‐promoted Cu‐containing catalysts (Cu_xNi_y‐MgAlO) for furfural (FFR) hydrogenation were prepared from the hydrotalcite‐like precursors, and characterized by X‐ray powder diffraction, inductively‐coupled plasma atomic emission spectroscopy, N₂ adsorption‐desorption, UV‐Vis diffuse reflectance spectra and temperature‐programmed reduction with H₂ in the present work. The obtained catalysts were observed to exhibit a better catalytic property than the corresponding Cu‐MgAlO or Ni‐MgAlO samples in FFR hydrogenation, and the CuNi‐MgAlO catalyst with the actual Cu and Ni loadings of 12.5 wt% and 4.5 wt%, respectively, could give the highest FFR conversion (93.2%) and furfuryl alcohol selectivity (89.2%). At the same time, Cu⁰ species from the reduction of Cu²⁺ ions in spinel phases were deduced to be more active for FFR hydrogenation.     

A Bio‐inspired Cu4O4 Cubane: Effective Molecular Catalysts for Electrocatalytic Water Oxidation in Aqueous Solution

Inspired by the cubic Mn₄CaO₅ cluster of natural oxygen‐evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts, especially M₄O₄ cubane‐like clusters (M=transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M₄O₄ clusters, however, copper‐based molecular catalysts are poorly understood. Now, bio‐inspired Cu₄O₄ cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with a turnover frequency (TOF) of 267 s^?1 for [(L_Gly‐Cu)₄] at 1.70 V and 105 s^?1 for [(L_Glu‐Cu)₄] at 1.56 V. Electrochemical and spectroscopic study revealed a successive two‐electron transfer process in the Cu₄O₄ cubanes to form high‐valent Cu^III and Cu^IIIO^. intermediates during the catalysis.     

Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu‐SSZ‐13

Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged Cu^II ions evidence both Cu^II and Cu^I ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH₃ together are necessary for Cu^II reduction to Cu^I. DFT calculations show that NO‐assisted NH₃ dissociation is both energetically favorable and accounts for the observed Cu^II reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu^I upon reduction, which we quantify in separate titration experiments. Both NO and O₂ are necessary for oxidation of Cu^I to Cu^II, which DFT suggests to occur by a NO₂ intermediate. Reaction of Cu‐bound NO₂ with proximal NH₄⁺ completes the catalytic cycle. N₂ is produced in both reduction and oxidation half‐cycles.     

Postsynthetic Metal and Ligand Exchange in MFU‐4l: A Screening Approach toward Functional Metal–Organic Frameworks Comprising Single‐Site Active Centers

The isomorphous partial substitution of Zn²⁺ ions in the secondary building unit (SBU) of MFU‐4l leads to frameworks with the general formula [M_xZn_(5–x)Cl₄(BTDD)₃], in which x≈2, M=Mn^II, Fe^II, Co^II, Ni^II, or Cu^II, and BTDD=bis(1,2,3‐triazolato‐[4,5‐b],[4′,5′‐i])dibenzo‐[1,4]‐dioxin. Subsequent exchange of chloride ligands by nitrite, nitrate, triflate, azide, isocyanate, formate, acetate, or fluoride leads to a variety of MFU‐4l derivatives, which have been characterized by using XRPD, EDX, IR, UV/Vis‐NIR, TGA, and gas sorption measurements. Several MFU‐4l derivatives show high catalytic activity in a liquid‐phase oxidation of ethylbenzene to acetophenone with air under mild conditions, among which Co‐ and Cu derivatives with chloride side‐ligands are the most active catalysts. Upon thermal treatment, several side‐ligands can be transformed selectively into reactive intermediates without destroying the framework. Thus, at 300 °C, Co^II‐azide units in the SBU of Co‐MFU‐4l are converted into Co^II‐isocyanate under continuous CO gas flow, involving the formation of a nitrene intermediate. The reaction of Cu^II‐fluoride units with H₂ at 240 °C leads to Cu^I and proceeds through the heterolytic cleavage of the H₂ molecule.     

A Supported Copper Hydroxide on Titanium Oxide as an Efficient Reusable Heterogeneous Catalyst for 1,3‐Dipolar Cycloaddition of Organic Azides to Terminal Alkynes

An easily prepared supported copper hydroxide on titanium oxide (Cu(OH)_x/TiO₂) showed high catalytic performance for the 1,3‐dipolar cycloaddition of organic azides to terminal alkynes in non‐polar solvents under anaerobic conditions. The reactions of various combinations of organic azides (four examples, including aromatic and aliphatic ones) and terminal alkynes (eleven examples, including aromatic, aliphatic, and double bond‐containing ones) exclusively proceeded to give the corresponding 1,4‐disubstituted‐1,2,3‐triazole derivatives in a completely regioselective manner. For the transformation of benzyl azide and ethynylbenzene with 0.12 mol % of Cu(OH)_x/TiO₂, the turnover frequency was 505 h^?1 and the turnover number reached up to 800. These values were the highest among those with previously reported heterogeneous catalysts including Cu(OH)_x/Al₂O₃. The observed catalysis was truly heterogeneous and the retrieved catalyst after the reaction could be reused at least three times with retention of its high catalytic performance. It was confirmed by the UV/Vis spectrum of Cu(OH)_x/TiO₂ and the amount of diyne formed that the Cu^II species in Cu(OH)_x/TiO₂ were reduced to Cu^I species by the alkyne–alkyne homocoupling at the initial stage of the reaction (during the pretreatment of Cu(OH)_x/TiO₂ with an alkyne). The catalytic reaction rate for the 1,3‐dipolar cycloaddition linearly increased with an increase in the amount of in situ generated Cu^I species. Therefore, the in situ generated Cu^I species would be the catalytically active species for the present 1,3‐dipolar cycloaddition.     

Optimized Pt-MnOx interface in Pt-MnOx/3DOM-Al2O3 catalysts for enhancing catalytic soot combustion

The catalysts of three-dimensionally ordered macroporous (3DOM) Al₂O₃-supported core-shell structured Pt@MnO_x nanoparticles (3DOM-Pt@MnO_x/Al₂O₃) were successfully prepared by the gas bubbling-assisted membrane reduction-precipitation (GBMR/P) method. Pt@MnO_x core-shell nanoparticles (NPs) are highly dispersed on the inner surface of 3DOM-Al₂O₃ support. Pt@MnO_x/3DOM-Al₂O₃ catalysts, which combine both advantages of high-efficiency soot-catalyst contact by 3DOM-Al₂O₃ structure and the abundant active sites by the optimized Pt-MnO_x interface, exhibit high catalytic activities for soot combustion, and the catalytic activities are strongly dependent on the thickness of MnO_x shell. Among the catalysts, 3DOM-Pt@MnO_x/Al₂O₃-1 catalyst with optimized Pt-MnO_x interface shows the highest catalytic activity for soot combustion, i.e., its values of T₅₀ and S_CO2^m are 351 °C and 98.6%, respectively. The highest density of Pt-MnO_x active sites for adsorption-activation of gaseous O₂ is responsible for enhancing catalytic activity for soot combustion. Pt@MnO_x/3DOM-Al₂O₃ catalysts are promising to practical applications for the emission reduction of soot particles.     

Catalytic combustion of diesel soot over perovskite-type catalyst: Potassium titanates

Potassium titanates with a high crystallinity were successfully prepared by the sol-gel method and characterized by XRD, SEM, and BET surface area measurements. K₆Ti₄O₁₁, K₂Ti₂O₅, K₂Ti₄O₉ were found to have better soot oxidation performance compared with Pt/TiO₂ and CeO₂ based catalysts. K₂Ti₂O₅ may be an excellent candidate for soot oxidation due to its high oxidation activity, water-stability, resistance to sulfur poisoning and economical advantages. Certain amount of NO _x can contribute to the catalytic combustion of diesel over potassium titanates, implying that K₂TiO₅ may be a kind of catalyst for simultaneous removal of NO _x and soot.