Palladium Nanoparticles Supported on a Porous Organic Polymer: An Efficient Catalyst for Suzuki‐Miyaura and Sonogashira Coupling Reactions

A new porous organic polymer (POP) with high thermal stability and large surface area has been synthesized and applied in the preparation of Pd/POP catalyst. Pd/POP was characterized by XRD, TGA, SEM and TEM. The catalyst consists of highly dispersed palladium nanoparticles of 0.9–4 nm size on POP with a large surface area of 650 m²/g. It presents high catalytic activity for Suzuki‐Miyaura and Sonogashira reactions. The catalyst was reusable for three to five times without significant loss of activity.     

Pd@tetrahedral hollow magnetic nanoparticles coated with N‐doped porous carbon as an efficient catalyst for hydrogenation of nitroarenes

Hollow magnetic nanoparticles (MNPs) with tetrahedral morphology were synthesized and then covered by a shell prepared by coating with melamine–formaldehyde followed by the introduction of glucose‐derived carbon. Subsequently, Pd nanoparticles were immobilized and the core–shell nanocomposite was carbonized. The obtained magnetic catalyst was successfully applied for the hydrogenation of nitroarenes in aqueous media. To investigate the effects of the morphology of MNPs, the nature of carbon shell, and the order of incorporation of Pd nanoparticles, several control catalysts, including the MNPs with different morphologies (disc‐like and cylinder); MNPs coated with different shells (sole glucose‐derived carbon or melamine–formaldehyde carbon shell); and a nanocomposite, in which Pd was immobilized after carbonization, were prepared and examined as catalyst for the model reaction. To justify the observed different catalytic activities of the catalysts, their Pd loadings, leaching, and specific surface areas were compared. The results confirmed that tetrahedral MNPs coated with porous N‐rich carbon shell exhibited the best catalytic activity. The high catalytic activity of this catalyst was attributed to its high surface area and the interaction of N‐rich shell with Pd nanoparticles that led to the higher Pd loading and suppressed Pd leaching.     

Size control and catalytic activity of highly dispersed Pd nanoparticles supported on porous glass beads

This paper presents a novel in situ method to prepare monodispersed palladium nanoparticles supported on porous glass beads with an egg-shell structure at room temperature. This method integrates two processes of ion exchange and reduction in one step just by changing the solvent from water to alcohol. The monodispersed Pd nanoparticles around 3.75 nm in diameter with a face-centered cubic structure have been successfully prepared. The adsorption capacity for palladium reached 55.00 ± 0.55 mg/g in ethanol, which was 26 times larger than that in water. These Pd nanoparticles supported on porous glass beads showed an excellent catalytic performance through the hydrogenation of cyclohexene. In addition, this in situ method was also successfully applied to prepare monodispersed silver and gold nanoparticles supported on porous glass beads. Overall, this facile method provided an alternative for preparing a supported nanoparticle catalyst in a green way.     

Highly Porous Amidoximed Carbon Nanofibers Supported Palladium(0) Nanoparticle Catalyzed Heck Reaction

Highly porous amidoximed carbon nanofibers(AOCNFs), which were fabricated via a conventional electrospinning technique followed by chemically modification, impregnation-reduction and carbonization process, had been used for the immobilization of palladium nanoparticles(Pd NPs) catalyst. During the carbonization process, polystyrene(PS) was selectively decomposed from bicomponent fibers, generating porous fibers. Fourier transform infrared spectroscopy(FTIR) result revealed the functional groups on PAN-PS fibers(PAN=polyacrylonitrile), AOPAN-PS fibers and AOCNFs; scanning electron microscopy(SEM) was used to observe the morphology of all stages of nanofibers; transmission electron microscopy(TEM) result gave the structure of through-hole morphology clearly visible and the dispersion of Pd NPs on the surface of nanofibers; and X-ray photoelectron spectra(XPS) confirmed that Pd nanoparticles on the surface of AOCNFs was of the metallic state. Moreover, the as-prepared catalyst exhibited high catalytic activity and efficient recycle for Heck coupling reactions between iodobenzene and acrylates.     

Pyrazine Derivative as Supramolecular Host for Immobilization of Palladium Nanoparticles for Efficient Suzuki Coupling

Palladium nanoparticles (NPs) have been extensively explored as unique catalyst for carbon-carbon coupling reactions. Nonetheless, because of extreme tendency of nanoparticles to undergo agglomeration, the immobilization of these metal NPs on organic frameworks is an important area of research. The present investigation demonstrates the synthesis of pyrazine derivative PYZ - TA as a supramolecular host for holding co-released Pd NPs derived from the original catalyst (Pd(II)) under standard Suzuki coupling. Unprecedent, physical bars are not required to capture Pd NPs within the pores of supramolecular host. The as obtained catalyst PYZ - TA@Pd exhibits high potential to undergo self-assembly in solid as well as in liquid state. The PYZ - TA@Pd ensemble shows high catalytic activity and recyclability (up to seven cycles) in Suzuki-Miyaura coupling reactions using low palladium loading and provides the corresponding products in excellent yields (up to 98 %). Therefore, this study provides an efficient strategy to develop an easy to synthesize palladium centered solid catalyst through coordination between organic host and Pd NPs.     

Keggin ion mediated synthesis of hydrophobized Pd nanoparticles for multifunctional catalysis

Development of simple and reliable protocols for the synthesis of organically soluble catalytically active metal nanoparticles is an important aspect of research in nanomaterials. We demonstrate herein the formation of Pd nanoparticles by reduction of aqueous Pd(NO(3))(2) by photoexcited Keggin ions (phosphotungstate anions). This results in the formation of Pd nanoparticles capped with with Keggin ions that render the particles negatively charged. The Keggin ion capped Pd nanoparticles may then be phase transferred into nonpolar organic solvents such as toluene by electrostatic complexation with cationic surfactants such as octadecylamine at the liquid-liquid interface. This results in a new class of catalyst wherein both the Pd core and Keggin ion shell may be used in a range of catalytic reactions leading to a truly multifunctional catalyst dispersible in organic solvents.     

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).     

乙二胺功能化纤维素负载纳米钯催化Suzuki反应的研究

以氯化纤维素为原料, 通过与乙二胺的胺化反应制得乙二胺功能化纤维素(Cell-EDA), 然后再将胺化纤维素在氯化钯乙醇溶液中反应可以方便制备得到乙二胺功能化纤维素负载的纳米钯催化剂(Cell-EDA-Pd0). 用SEM, TEM等分析方法对所制备的催化剂进行了表征; TEM分析表明乙二胺功能化纤维素负载的纳米钯呈球形, 粒径在10～20 nm左右. 实验结果表明, Cell-EDA-Pd0催化剂对空气稳定, 无需在惰性气体的保护下就能有效地催化芳基硼酸与卤代芳烃的Suzuki交叉偶联反应, 催化剂易回和收重复使用, 催化剂重复使用6次催化活性没有明显降低.     

Nanoporous phenanthroline polymer locked Pd as highly efficient catalyst for Suzuki-Miyaura Coupling reaction at room temperature

Because of the intrinsic advantages, Suzuki coupling reactions have been one of the most popular coupling reactions in organic synthesis, however developing a high-performance heterogeneous catalyst for Suzuki coupling reactions in aqueous media at low temperature (e.g. room temperature) is still a challenge. Herein, a heterogeneous catalyst with coordinated Pd as active site and a designed conjugated phenanthroline based porous polymer (CPP) as support was fabricated. Systematically investigation on CPP support by Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Transmission electron microscopy (TEM), N₂ adsorption–desorption isotherm and Scanning electron microscopy (SEM) show that the derived CPP catalyst support owns a porous structure, moderately good surface area (141 m²/g) and an excellent thermal stability. As a heterogeneous catalyst for the synthesis of biphenyl derivatives via Suzuki coupling, Pd/CPP achieves an excellent catalytic performance and recycling ability towards Suzuki reaction of various reactants at room temperature in ethanol-water medium.     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

A Porous Organic Poly(triphenylimidazole) Decorated with Palladium Nanoparticles for the Cyanation of Aryl Iodides

A new porous organic poly(triphenylimidazole), PTPI‐Me, was prepared through a Yamamoto self‐coupling reaction of 2,4,5‐tris‐(4‐bromophenyl)‐1‐methyl‐1H‐imidazole (TPI‐Me) in the presence of bis(1,5‐cyclooctadiene)nickel(0). The polymer was subsequently decorated with Pd nanoparticles (NPs) to afford a heterogeneous cyanation catalyst, Pd@PTPI‐Me. Pd NPs with an average diameter of 2.7 nm were grown within the PTPI‐Me framework, owing to the coordination of the imidazole rings to the Pd species. The resultant Pd@PTPI‐Me catalyst, with a Pd loading of 0.13 mmol g^?1, exhibited superior catalytic activity for the cyanation of aryl iodides. More importantly, the heterogeneous catalyst was also readily recycled and displayed negligible deactivation after five cycles.     

Aerobic oxidation of benzyl alcohols through biosynthesized palladium nanoparticles mediated by Oak fruit bark extract as an efficient heterogeneous nanocatalyst

In this study, green synthesis of Pd nanoparticles (NPs) is outlined through application of Oak fruit bark extract as a reducing, capping and stabilizing agent. The characteristics and properties of the biosynthesized Pd NPs were revealed by FESEM, EDX, XRD, TEM, UV–Vis, and FT-IR spectroscopies. So that, UV–Vis spectroscopy of the Pd colloidal solution confirmed reduction of Pd ions, and XRD and TEM analysis identified fcc unit cell structure forming 5–7 nm spherical Pd NPs. Furthermore, catalytic activity of the prepared catalyst was investigated through aerobic oxidation of alcohols, as model reactions. Catalytic evaluations demonstrated achievement of good yields from primary and secondary benzyl alcohols. In general, the devised synthesis method is advantageous from several perspectives. For example, the synthesized catalysts give high product yields and are efficient, they eliminate the need for surfactant, chemical reductants, ligand and organic solvents, the approach is economically inexpensive, it results in cleaner reaction profiles, application of the simply prepared heterogeneous catalyst is convenient, and the catalyst is recoverable and reusable for at least six times without any significant loss of its catalytic activity.     

醇在载钯碳化钨/碳纳米管催化剂上的氧化

用交替微波法制备了碳化钨与多壁碳纳米管复合材料(WC/MWCNT),以该材料为载体制备了Pd基催化剂(Pd-WC/MWCNT),并将催化剂用于醇的催化氧化反应.结果表明,Pd-WC/MWCNT催化剂对乙醇的催化氧化活性是Pd/C催化剂的5倍.交换电流密度测量和反应活化能计算表明,Pd-WC/WIWCNT催化剂对乙醇催化氧化的交换电流密度比Pd/C大两个数量级,反应活化能低一倍以上.Pd-WC/MWCNT催化剂催化氧化乙醇性能的大幅度提高是碳化钨与Pd颗粒的协同效应和碳纳米管的结构效应共同作用的结果.     

Immobilized Pd on a NHC functionalized metal–organic framework MIL-101(Cr): an efficient heterogeneous catalyst in Suzuki−Miyaura coupling reaction in water

A novel Pd−NHC functionalized metal–organic framework (MOF) based on MIL-101(Cr) was synthesized and used as an efficient heterogeneous catalyst in the C-C bond formation reactions. Using this heterogeneous Pd catalyst system, the Suzuki−Miyaura coupling reaction was accomplished well in water, and coupling products were obtained in good to excellent yields in short reaction time. The Pd−NHC−MIL-101(Cr) was characterized using some different techniques, including Fourier transform-infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy, inductively coupled plasma and elemental analysis. The microscopic techniques showed the discrete octahedron structure of MIL-101(Cr), which is also stable after chemical modification process to prepare the catalyst system. The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the structure of the catalyst, while no reducing agent was used. It seems that the NHC groups and imidazolium moieties in the structure of the MOF can reduce Pd (II) to Pd (0) species. This modified MOF substrate can also prevent aggregation of Pd nanoparticles, resulting in high stability of them in organic transformation. The Pd−NHC−MIL-101(Cr) catalyst system could be simply extracted from the reaction mixture, providing an efficient synthetic method for the synthesis of biaryls derivatives using the aforementioned coupling reaction. The Pd−NHC−MIL-101(Cr) catalyst could be recycled in this organic reaction with almost consistent catalytic efficiency.     

UC Pd: A New Form of Pd/C for Sonogashira Couplings

Screening of different sources of Pd/C shows reagents of highly variable nanoparticle sizes and oxidation states of the metal. Typically, catalysts with higher surface area are viewed as likely to be the more reactive. In this paper a new form of Pd/C, “UC Pd” is described that is shown to contain larger nanoparticles yet it is the most reactive catalyst of those sold commercially for Sonogashira coupling reactions. UC Pd functions efficiently in the absence of a copper co‐catalyst, under very mild and “green” conditions using inexpensive 95 % EtOH at 50 °C. It is also the only form of Pd/C that can be recycled. In side‐by‐side reactions with several commercially available forms of Pd/C, none compete successfully with UC Pd under standardized conditions. Physical data obtained from extensive surface analysis using TEM, XRD, XPS, and CO‐TPD measurements lead to an explanation behind the unique reactivity of this new recyclable form of Pd/C.     

金属有机骨架高温自还原制备高性能等级孔碳负载Co基催化剂

以钴基金属有机框架为前驱体, 利用一步高温碳化自还原法, 通过精确调控碳化过程, 实现等级孔道结构及钴纳米颗粒分散性的可控调节, 制备出高催化活性及产物选择性的等级孔碳负载Co基催化剂. 研究发现, 600 ℃碳化后的催化剂为具有高比表面积的等级孔道结构和高分散的钴纳米颗粒, 在选择性催化1,3-丁二烯加氢反应中, 丁二烯完全转化温度低至60 ℃, 对应丁烯的选择性高达61%, 实现了低温高选择性催化加氢.     

聚吡咯改性炭载Pd催化剂促进甲酸电氧化

直接甲酸燃料电池(DFAFC)阳极活性炭载Pd催化剂活性组分易聚集,分散差且存在炭载体的电腐蚀作用,造成催化活性低稳定性差。 为解决上述问题,本文通过调控炭载Pd催化剂的载体改善催化活性和稳定性。 采用低温化学氧化法制备了聚吡咯(PPy)与活性炭复合材料,在聚合过程中加入活性炭,经过高温热解聚吡咯形成复合碳载体负载Pd催化剂,并表征了热解聚吡咯碳修饰催化剂表面形貌,发现聚吡咯修饰后的催化剂载体表面氮元素以吡咯氮的形式存在,催化剂活性组分Pd纳米粒子可稳定在2.25 nm。 通过甲酸电催化氧化性能测试,结果表明,Pd单位质量比活性比Pd/C催化剂提高了2.5倍。     

The controllable preparation of electrospun carbon fibers supported Pd nanoparticles catalyst and its application in Suzuki and Heck reactions

The palladium nanoparticles/carbon nanofibers(Pd NPs/CNFs) catalyst was prepared by the electrospinning method, the hydrazine hydrate solution reduction in an ice bath environment, the high temperature carbonization. The catalyst was characterized by X-ray diffraction(XRD), fieldemission scanning electron microscope(FE-SEM), and transmission electron microscopy(TEM). The nanofibers are not cross-linked and arranged in order. The surface of Pd NPs/CNFs is smooth, and it can be observed that a large number of particles were loaded and well-dispersed in carbon fiber matrix, and the particle distribution is uniform. The activity center of catalyst is Pd(0). The Pd NPs/CNFs exhibited a high efficiency, good reusability and stability in the Suzuki and Heck reactions. It can be used for at least five consecutive runs without significant loss of its catalytic activity. The good recyclability of Pd NPs/CNFs provides a way to greatly reduce the cost of the catalyst.     

A simple and greener approach for the synthesis of PVC supported Pd (0): application to Heck and Sonogashira reactions in water

Preparation of PVC-supported Pd nanoparticles through the reduction of PdCl₂ by a non-toxic and eco-friendly route, employing sodium formate and NaOH in ethanol–water system has been described. The prepared PVC supported Pd nanoparticles were employed as catalyst in the cross coupling reactions, that is, Heck and Sonogashira reactions in water medium to afford the respective products in good to excellent yields.     

Fabrication of Nitrogen‐Doped Mesoporous‐Carbon‐Coated Palladium Nanoparticles: An Intriguing Electrocatalyst for Methanol and Formic Acid Oxidation

Inspired by the attractive catalytic properties of palladium and the inert nature of carbon supports in catalysis, a concise and simple methodology for in situ nitrogen‐doped mesoporous‐carbon‐supported palladium nanoparticles (Pd/N‐C) has been developed by carbonizing a palladium dimethylglyoximate complex. The as‐synthesized Pd/N‐C has been exfoliated as a fuel cell catalyst by studying the electro‐oxidation of methanol and formic acid. The material synthesized at 400 °C,namely, Pd/N‐C‐400,exhibitssuperior mass activity and stability among catalysts synthesized under different carbonization temperaturesbetween300 and 500 °C. The unique 1D porous structure in Pd/N‐C‐400 helps better electron transport at the electrode surface, which eventually leads to about five times better catalytic activity and about two times higher stability than that of commercial Pd/C. Thus, our designed sacrificial metal–organic templatedirected pathway becomes a promising technique for Pd/N‐C synthesis with superior catalytic performances.