氧同位素交换及其在多相催化氧化反应研究中的应用

简单介绍了氧同位素交换技术及其在多相催化氧化反应机理研究中的应用     

Suzuki反应中催化体系的研究进展

随着过渡金属催化的交叉偶联反应的出现,有机合成化学在20世纪的最后25年得到了快速的发展,并且这些反应的重要性被普遍认可.其中,Suzuki偶联反应因其多功能性、兼容性和对包括材料科学和药物合成在内的多种学科的关键贡献,而占据了更加特殊的地位.尽管到2010年为止Suzuki反应已取得重大进展,但随着可持续和绿色化学发展的需求,Suzuki反应的催化体系仍待进一步优化提高.这里概述的催化剂为C-C键的构建提供了方便和绿色的合成途径.在这篇综述中,我们总结了科研工作者对于Suzuki反应在改进催化剂制备策略、优化催化反应条件、提高催化剂重复利用性能和降低催化剂成本方面做的一系列研究.     

Ultrathin Spinel‐Structured Nanosheets Rich in Oxygen Deficiencies for Enhanced Electrocatalytic Water Oxidation

Electrochemical water splitting is a clean technology for H₂ fuels, but greatly hindered by the slow kinetics of the oxygen evolution reaction (OER). Herein, a series of spinel‐structured nanosheets with oxygen deficiencies and ultrathin thicknesses were designed to increase the reactivity and the number of active sites of the catalysts, which were then taken as an excellent platform for promoting the water oxidation process. Theoretical investigations showed that the oxygen vacancies confined in the ultrathin nanosheet could lower the adsorption energy of H₂O, leading to increased OER efficiency. As expected, the NiCo₂O₄ ultrathin nanosheets rich in oxygen vacancies exhibited a large current density of 285 mA cm^?2 at 0.8 V and a small overpotential of 0.32 V, both of which are superior to the corresponding values of bulk samples or samples with few oxygen deficiencies and even higher than those of most reported non‐precious‐metal catalysts. This work should provide a new pathway for the design of advanced OER catalysts.     

Water Oxidation with Molecularly Defined Iridium Complexes: Insights into Homogeneous versus Heterogeneous Catalysis

Molecularly defined Ir complexes and different samples of supported IrO₂ nanoparticles have been tested and compared in the catalytic water oxidation with cerium ammonium nitrate (CAN) as the oxidant. By comparing the activity of nano‐scaled supported IrO₂ particles to the one of organometallic complexes it is shown that the overall activity of the homogeneous Ir precursors is defined by both the formation of the homogeneous active species and its conversion to Ir^IV ‐ oxo nanoparticles. In the first phase of the reaction the activity is dominated by the homogeneous active species. With increasing reaction time, the influence of nano‐sized Ir ‐ oxo particles becomes more evident. Notably, the different conversion rates of the homogeneous precursor into the active species as well as the conversion into Ir‐oxo nanoparticles and the different particle sizes have a significant influence on the overall activity. In addition to the homogeneous systems, IrO₂@MCM‐41 has also been synthesized, which contains stabilized nanoparticles of between 1 and 3 nm in size. This latter system shows a similar activity to IrCl₃ ? xH₂O and complexes 4 and 5 . Mechanistic insights were obtained by in situ X‐ray absorption spectroscopy and scanning transmission electron microscopy.     

Prefunctionalized Porous Organic Polymers: Effective Supports of Surface Palladium Nanoparticles for the Enhancement of Catalytic Performances in Dehalogenation

Three porous organic polymers (POPs) containing H, COOMe, and COO^? groups at 2,6‐bis(1,2,3‐triazol‐4‐yl)pyridyl (BTP) units (i.e., POP‐1, POP‐2, and POP‐3, respectively) were prepared for the immobilization of metal nanoparticles (NPs). The ultrafine palladium NPs are uniformly encapsulated in the interior pores of POP‐1, whereas uniform‐ and dual‐distributed palladium NPs are located on the external surface of POP‐2 and POP‐3, respectively. The presence of carboxylate groups not only endows POP‐3 an outstanding dispersibility in H₂O/EtOH, but also enables the palladium NPs at the surface to show the highest catalytic activity, stability, and recyclability in dehalogenation reactions of chlorobenzene at 25 °C. The palladium NPs on the external surface are effectively stabilized by the functionalized POPs containing BTP units and carboxylate groups, which provides a new insight for highly efficient catalytic systems based on surface metal NPs of porous materials.     

活化温度对CuBTC催化CO氧化反应性能的影响(英文)

考察了金属有机骨架材料CuBTC(BTC为均苯三酸)催化CO氧化的反应性能,发现CuBTC对CO氧化反应表现出良好的催化活性,且CuBTC样品的活化温度对其催化活性的影响很大.原位漫反射红外光谱、粉末X射线衍射、扫描电镜、热重分析和差示扫描量热结果表明,CO在CuBTC骨架中不饱和金属位点上的配位是加速CO氧化的主要原因,且这种不饱和金属位点越多,其催化活性越高.     

分子氧氧化醇的研究进展

鉴于分子氧具有经济、环保、易得的优势,本文从均相催化、多相催化以及新材料的角度阐述了近年来液态醇选择氧化到醛酮的进展。着重介绍了过渡金属作为活性组分构成的催化体系,较详细的对新催化材料的研究做了一下归类,并对其在醇的氧化反应中的应用做了介绍,认为传统催化领域的研究仍然具有魅力,同时新材料的开发与运用在未来的具有诱人的前景。     

Effects of Metal Electrode Support on the Catalytic Activity of Fe(oxy)hydroxide for the Oxygen Evolution Reaction in Alkaline Media

FeO_xH_y and Fe-containing Ni/Co oxyhydroxides are the most-active catalysts for the oxygen evolution reaction (OER) in alkaline media. However, the activity of Fe sites appears strongly dependent on the electrode-substrate material and/or the elemental composition of the matrix in which it is embedded. A fundamental understanding of these interactions that modulate the OER activity of FeO_xH_y is lacking. We report the use of cyclic voltammetry and chronopotentiometry to assess the substrate-dependent activity of FeO_xH_y on a number of commonly used electrode substrates, including Au, Pt, Pd, Cu, and C. We also evaluate the OER activity and Tafel behavior of these metallic substrates in 1 M KOH aqueous solution with Fe³⁺ and other electrolyte impurities. We find that the OER activity of FeO_xH_y varies by substrate in the order Au>Pd≈Pt≈Cu>C. The trend may be caused by differences in the adsorption strength of the Fe oxo ion on the substrate, where a stronger adhesion results in more adsorbed Fe at the interface during steady-state OER and possibly a decreased charge-transfer resistance at the FeO_xH_y-substrate interface. These results suggest that the local atomic and electronic structure of [FeO₆] units play an important role in catalysis of the OER as the activity can be tuned substantially by substrate interactions.     

Biomass Oxidation: Formyl CH Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves

An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C? H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C? C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates.     

Enhanced Peroxymonosulfate Activation by NixCo1-xOOH for Efficient Catalytic Oxidation of Organic Pollutants

Peroxymonosulfate(PMS) has received increasing attention as viable technology for recalcitrant organics removal from polluted waters. Although promising, alternative heterogeneous catalysts with stable structure, strong hydrophilicity, environmental friendliness and excellent catalytic performance are highly desirable to facilitate the wide industrialization of PMS. In this work, Ni doped CoOOH catalyst was employed as PMS activator. Ni dopant had a significant influence on the morphology, structure and catalytic performance of CoOOH. NiojCoo.gOOH exhibited the best catalytic performance. Reaction rate ofNio.2Coo.8OOH was 2, 4, and 4.4 times that of CoOOH, CoFe2O4 and CO3O4, respectively. Moreover, Ni。2C00.8OOH/PMS system had potential application to organic pollutants and displayed a great catalytic activity over a broader pH value(e.g., 4-10). More importantly, Ni doping accelerated the transfonnation of Co(Ⅲ) and Co(Ⅱ) and formed active species CoOH^+ and NiOH^+ which were responsible to the enhancement of PMS activation.OH, SO4^-:O2^- and 1^O2 were detected, indicating both non-radical and radical processes in the Nio.2Coo.8OOH/PMS system. These findings provide a promising alternative to mixed-metal oxyhydroxides catalysts for PMS activation, demonstrating a great potential in environmental remediation and wastewater treatment.     

Catalytic Consequences of the Thermodynamic Activities at Metal Cluster Surfaces and Their Periodic Reactivity Trend for Methanol Oxidation

The periodic reactivity trend and the connection of kinetics to the thermodynamic activity of oxygen are established for the oxidation of methanol on metal clusters. First‐order rate coefficients are a single‐valued function of the O₂‐to‐CH₃OH ratio, because this ratio, together with the rate constants for O₂ and CH₃OH activation, determine the oxygen chemical potential, thus the relative abundance of active sites and bulk chemical state of the clusters. CH₃OH activation rate constants on oxygen‐covered Ag, Pt, and Pd and on RuO₂ clusters vary with the metal–oxygen binding strength in a classical volcano‐type relation, because the oxygen‐binding strength directly influences the reactivities of oxygen as H abstractors during the kinetically relevant CH₃OH activation step. The differences in oxygen thermodynamic activity lead to five orders of magnitude variation in rates (Pt>Pd>RuO₂>Ag, 373 K), because of its strong effects on the activation enthalpy and more prominently activation entropy in CH₃OH activation.