Palladium Cations Research Articles

Fabrication of Kaolin Loaded Chitosan Hybrid Nanofibers for Recovery of Precious Palladium Cations from Aqueous Solution

Fabrication of Kaolin Loaded Chitosan Hybrid Nanofibers for Recovery of Precious Palladium Cations from Aqueous Solution

Unmatched Redox Activity of the Palladium-Doped Indium Oxide Oxygen Carrier for Low-Temperature CO2 Splitting.

The chemical conversion of CO2 into value-added products is the key technology to realize a carbon-neutral society. One representative example of such conversion is the reverse water-gas shift reaction, which produces CO from CO2. However, the activity is insufficient at ambient pressure and lower temperatures (<600 °C), making it a highly energy-intensive and impractical process. Herein, we report indium oxide nanofibers modified with palladium catalysts that exhibit significantly potent redox activities toward the reduction of CO2 splitting via chemical looping. In particular, we uncover that the doped palladium cations are selectively reduced and precipitated onto the host oxide surface as metallic nanoparticles. These catalytic gems formed operando make In2O3 lattice oxygen more redox-active in H2 and CO2 environments. As a result, the composite nanofiber catalysts demonstrate the reverse water-gas shift reaction via chemical looping at record-low temperatures (≤350 °C), while also imparting high activities (CO2 conversion: 45%). Altogether, our findings expand the viability of CO2 splitting at lower temperatures and provide design principles for indium oxide-based catalysts for CO2 conversion.

Dynamic structural evolution of MgO-supported palladium catalysts: from metal to metal oxide nanoparticles to surface then subsurface atomically dispersed cations.

Supported noble metal catalysts, ubiquitous in chemical technology, often undergo dynamic transformations between reduced and oxidized states-which influence the metal nuclearities, oxidation states, and catalytic properties. In this investigation, we report the results of in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, and other physical characterization techniques, bolstered by density functional theory, to elucidate the structural transformations of a set of MgO-supported palladium catalysts under oxidative treatment conditions. As the calcination temperature increased, the as-synthesized supported metallic palladium nanoparticles underwent oxidation to form palladium oxides (at approximately 400 °C), which, at approximately 500 °C, were oxidatively fragmented to form mixtures of atomically dispersed palladium cations. The data indicate two distinct types of atomically dispersed species: palladium cations located at MgO steps and those embedded in the first subsurface layer of MgO. The former exhibit significantly higher (>500 times) catalytic activity for ethylene hydrogenation than the latter. The results pave the way for designing highly active and stable supported palladium hydrogenation catalysts with optimized metal utilization.

Coordination-driven Synthesis of a Self-assembled Architecture Bearing Urea Groups from a Triply Helical Fe(II) Complex of a Tripodal Ligand and a Pd(II) Complex

Triply helical iron(II) complexes of a tripodal 2,2′-bipyridine ligand bearing 4-pyridyl urea groups have undergone coordination-driven self-assembly with palladium(II)-bis(1,3-diphenylphosphinopropane), dppp, units affording the 2:3 complex in an almost quantitative yield. In the coordination-driven self-assembled architecture, the 4-pyridyl moieties of the iron(II)-tris(2,2′-bipyridine) complexes coordinated to the palladium(II) cations ligated by dppp.

Palladium nanoparticles supported on cobalt(II,III) oxide nanocatalyst: High reusability and outstanding catalytic activity in hydrolytic dehydrogenation of ammonia borane

A new palladium(0) nanocatalyst is developed to enhance the catalytic efficiency of precious metal catalysts in hydrogen generation from the hydrolytic dehydrogenation of ammonia borane. Magnetically separable Pd0/Co3O4 nanocatalyst can readily be obtained by the reduction of palladium(II) cations impregnated on cobalt(II, III) oxide at room temperature. The obtained Pd0/Co3O4 nanocatalyst with 0.25% wt. palladium loading has outstanding catalytic activity with a record turnover frequency of 3048 min−1 in the releasing H2 from the hydrolysis of ammonia borane at 25.0 °C. They also provide outstanding reusability even after the tenth run of the hydrolysis of ammonia borane at 25.0 °C. The high activity and superb stability of magnetically isolable Pd0/Co3O4 nanoparticles are attributed to the favorable interaction of palladium with the surface of reducible cobalt oxide.

A Distinctive Pattern for Substituent Effects on Transition Metal Centers: Enhanced Electron-Donating Capacity of Cationic Palladium Species

A Distinctive Pattern for Substituent Effects on Transition Metal Centers: Enhanced Electron-Donating Capacity of Cationic Palladium Species

Fabrication of chitosan composite nanofibers for the recovery of precious palladium cations from aqueous solution

Fabrication of chitosan composite nanofibers for the recovery of precious palladium cations from aqueous solution

Kinetic and Thermodynamic Factors Influencing Palladium Nanoparticle Redispersion into Mononuclear Pd(II) Cations in Zeolite Supports

Palladium cations and nanoparticles supported on oxides and zeolites are used as catalysts and adsorbents for a wide range of chemical reactions of practical importance, with various and distinct active site requirements. Consequently, sintering and redispersion processes that interconvert site-isolated Pd cations and agglomerated nanoparticles underpin catalyst activation and deactivation phenomena, yet the influence of Pd nanoparticle size distribution and gas conditions on the thermodynamic and kinetic factors influencing such interconversion is imprecisely understood. Here, we prepare Pd nanoparticles of different particle size and distribution (normal, log–normal) supported on high-symmetry crystalline zeolites to access well-defined materials whose Pd site distributions can be quantitatively characterized by experiments and modeled accurately by theory. Ab initio thermodynamic modeling and isothermal (593–973 K) wet and dry air treatments of Pd-zeolites reveal that the widely observed deactivation in low-temperature hydrous environments reflects site interconversion thermodynamics that favor the agglomeration of isolated Pd cations into nanoparticles. Under high-temperature anhydrous conditions, experimental kinetic measurements and kinetic Monte Carlo simulations evince the preeminence of kinetic factors on Pd nanoparticle redispersion into cations, which proceeds at rates that are strongly influenced by the initial Pd particle size distribution and via a substrate diffusion-mediated Ostwald ripening process whereby Pd monomers are captured in an atom trapping process at anionic exchange sites (framework Al) in the zeolite support. These findings resolve longstanding questions regarding the roles of H2O and support interactions in Pd redispersion processes and identify strategies to enhance or suppress Pd site interconversion by modifying oxide supports and gas conditions.

Sorption of cationic complexes of palladium (II) from thiourea solutions

This paper looks at the sorption of cationic complexes [Pd(Thio)4]2+ (where Thio stands for thiourea) on sulfo cation exchanger KU-2-8. It takes 2 days for the Pd(II) static sorption capacity to start seeing constant values; the maximum Pd(II) static sorption capacity is 2.8 mmol/g. Solutions of acids, salts, thiourea and ammonia were used as eluents for Pd(II). By the Pd(II) static desorption efficiency, the solutions can be arranged as follows: 10% Thio solution in 10% HCl (69&ndash;70%) &gt; 6 M HCl (51&ndash;52%) &gt; saturated KCl solution (35&ndash;36%) &gt; 25% NH4Cl solution (6&ndash;7%)  1М H2SO4 (1&ndash;3%) 10% ammonia solution (0&ndash;1%). In the IR spectrum of the cation exchanger saturated with Pd(II) complexes, the adsorption bands of thiourea ligand appear alongside with the adsorption bands typical of the sorbent in a hydrogen form; the long-wave region contains an adsorption band at 377 cm&ndash;1, which the authors attribute to Pd &ndash; S stretching mode. A 23 cm&ndash;1 shift of the maximum of the adsorption band referring to the (ОН) stretching mode in the IR spectrum of the sorbent saturated with Pd(II) complexes into the long-wave region compared with the position of the (ОН) maximum in the spectrum of the hydrogen form sorbent is indicative of hydrogen bonding between the sulfo group of the sorbent and the amino group of the thiourea: S = O&middot;&middot;&middot;H &ndash; N. A relationship between the sorption capacity and the acidity of the initial solution, a comparison of IR spectra of the solid phases and analysis of free thiourea contained in the mother solutions confirm that the sorption process is based on cation exchange and that all 4 Thio molecules remain in the sorption complex. Tests were conducted in which the sorbent was used for dynamic separation of Pd(II) from a standard test thiourea solution containing copper and palladium cations. It is shown that copper cations get sorbed alongside with thiourea complexes of Pd(II). Such copper cations can be partially removed from the sorbent phase by washing it with 1 M sulphuric acid solution. It was found that the thermal decomposition of the sorbent saturated with complex Pd(II) ions results in the formation of black ball-shaped granules containing 76.0&ndash;82.5% of carbon; 4.0&ndash;4.5% of sulphur; 0.3&ndash;0.4% of hydrogen; 14.0&ndash;14.5% palladium; and a trace amount of nitrogen. According to the X-ray diffraction data on the product resultant from heat treatment of the sorbent saturated with thiourea complexes of Pd(II), palladium is present in the form of metal (Fm3m) (approximately 85% of the total concentration) and its oxide PdO (P4n2). These granules can be of interest as heterogeneous carbon-containing palladium catalysts.

Synthetic incorporation of palladium-nickel bimetallic nanoparticles within mesoporous silica/silica nanoparticles as efficient and cheaper catalyst for both cationic and anionic dyes degradation

Nickel-palladium bimetallic nanocrystallite supported mesoporous silica/silica nanoparticles (MSPs/MSNPs) made at a controlled ratio of Pd/Ni via organotrialkoxysilane mediated reduction of palladium cations are reported. The organotrialkoxysilane serve as a template for the stabilization and formation of bimetallic Pd-Ni nanocrystallite within MSPs/MSNPs that are characterized by TEM, EDX, HR-SEM, HR-MS, XRD, BET and Elemental mapping analysis, kinetic analysis for degradation of both cationic and anionic dyes, i.e., rhodamine B and congo red, respectively. The nanocrystallite inserted MSNPs of particle diameter 200 nm justify faster degradation with rate constant to the order of 6.9 x10−2s−1 as compared to that for MSPs of 50 µm to the order of 3.2 x10−2 s−1 for 15 ppm Rh B within 50 s as compared to that for mesoporous silica of 50 µm within 110 s under similar conditions with analogous observation for the degradation of congo red. Heterogeneous support is fully recyclable and shows 100% catalytic activity even after five subsequent applications. The degradation dynamics have further been evaluated based on fluorescent spectra and HR-MS analysis.

Phase transformations of Fe(ІІ)-Fe(III) layered dоuble hydroxides of corrosion origin in the aqueous solutions of platinum and palladium

One of the urgent scientific problems is the development of new or alternative to the well-known methods оf the synthesis of biocompatible substances and composites with unique complexes of physicochemical properties (optical, magnetic, catalytic, electrical, bactericidal). Promising substances for the production of compounds of this class are Fe (II)-Fe (III) layered double hydroxides (LDHs) or Green Rust.At present, Green Rust suspensions are already used as nanoreactors for the one stage reduction of precious metal particles (gold and silver), the production of magnetite doped with precious metals and the synthesis of shell nanocomposites. The advantages of using Fe(II)-Fe(III) LNG structures as a reducing agent are the absence of the need to introduce into the system foreign components, such as anions of iron salts, organic substances, including surfactants, as well as the simplicity of the synthesis procedure, carried out without the use of expensive equipment.While the processes of formation of shell nanocomposites Fe3O4&Ag0 and Fe3O4&Au0 in Green Rust suspensions, their physicochemical properties, experience and prospects for practical use in biomedical research are covered in the literature in detail, the lack of comprehensive data on the structure and properties of shell composites based on particles of magnetite of corrosion origin and clusters of platinum and palladium, or magnetite doped with platinum group metals, still remain an unsolved part of this scientific problem.Therefore, the aim of this study was to determine the composition and physicochemical properties of the products of phase transformations of hydroxycarbonate Green Rust of corrosion origin in its contact with aqua forms of platinum and palladium under conditions of free air in the reaction zone.To obtain the primary phase of hydroxycarbonate Green Rust, a disk device was used, the working part of which is made of steel 3. During the synthesis procedure, the steel disk was alternately in contact with aqueous solution and air. Before the start of each experiment, the disk was treated mechanically and chemically to remove the oxide layer and activate the surface of the carbon alloy. The build-up of the GR(CO3)2- layer was performed under conditions of contact of the steel surface with distilled water for an hour, after which the dispersion medium was changed to aqueous solutions of noble metals.Six aqueous sodium chlorine platinate Na2[PtCl6] ‧ 6H2O in the concentration range (Pt 4+) from 0.5 to 10 mg/dm3 was used to obtain platinum-containing solutions, and H2[PdCl4] and PdCl2 with concentrations (Pd 2+) from 0.1 to 10 mg/dm3 were selected to obtain palladium-containing solutions, respectively. The synthesis was performed before the transition of the system to a steady state (70 hours). The studies were based on the following methods: X-ray phase analysis and X-ray fluorescence spectroscopy (X-ray diffraction), thermogravimetry (TG-DTA), photocolorimetry, electrokinetic studies, scanning electron microscopy (SEM), magnetic field and force microscopy, magnetometry.As a result of the conducted experiments, the processes of phase transformations of Fe(II)-Fe(III) LNG of hydroxycarbonate composition of corrosion origin in the presence of aquaforms of platinum and palladium were investigated. The formation of nanosized particles of magnetite on the surface of steel and oxyhydroxides of iron, relics of Fe(II)-Fe(III) LNG and particles of reduced noble metals - in the film of its near-surface layer have been established. It is determined that the phase formation in the system is accompanied by the activation of electrode processes on the steel surface, which lead to the accumulation of Fe2 + cations and hydroxyl anions in the dispersion medium. The typical course of exogenous oxidation of iron-containing compounds is elucidated by thermogravimetry. It is shown that the entry of platinum and palladium cations into the structure of magnetite significantly affects the value of its electrokinetic potential. The method of magnetometry proved that the particles of platinum-doped magnetite have nanometer sizes and belong to superparamagnetic, which opens up prospects for their practical use in biomedicine.

Synthesis and properties of Cu- and Pd-complexes of cyclen conjugates with pheophorbide and bacteriopheophorbide

Objectives. Chlorin and bacteriochlorin photosensitizers are effective agents for cancer photodynamic therapy and fluorescence imaging. They are also excellent chelators forming stable metal complexes. Besides, 64 Cu and 109 Pd isotopes can serve as emitters for nuclear medicine. Chelation of these metals with cyclen conjugates with chlorin and bacteriochlorin photosensitizers can become a simple and universal strategy for the synthesis of diagnostic and therapeutic radiopharmaceuticals for nuclear medicine. This article reports on the synthesis of similar Cu and Pd complexes of cyclen conjugates with pheophorbide and bacteriopheophorbide and the study of their photophysical properties. Methods. Metalation of cyclen conjugates was carried out with palladium and copper acetates. For bacteriochlorins, 6-O-palmitoyl-L-ascorbic acid was additionally used as a reducing agent. MALDI mass spectrometry, which was carried out on a time-of-flight mass spectrometer Bruker Ultraflex TPF/TOF and a Bruker Daltonics Autoflex II confirmed the structure of the compounds obtained Electronic absorption spectra were obtained on a Shimadzu 3101 spectrophotometer. Fluorescence and phosphorescence spectra were obtained on a FluoTime 300 PicoQuant spectrofluorometer. Results. Photophysical studies of metal complexes showed that the introduction of palladium cations quenches fluorescence and increases the quantum yield of singlet oxygen generation to 0.98 for the chlorin conjugate. Besides, it decreases the quantum yield of fluorescence to 0.10 and increases the quantum yield of singlet oxygen generation to 0.72 for the bacteriochlorin conjugate. Introducing a copper cation to cyclen conjugates with pheophorbide and bacteriopheophorbide leads to photophysical characteristics quenching. Conclusions. Due to the stability of the synthesized metal complexes in acidic media, as well as the short metalation time (5, 20, 10, and 15 minutes) it is reasonable to expect the successful development of effective imaging agents for positron emission tomography and radionuclide therapy. In addition, the residual fluorescence of bacteriochlorins makes it possible to use fluorescence diagnostics in combination with these methods.

Selective Naked-Eye Fluorescein-Based Chemosensor for the Detection of Pd2+ Cations

Highly sensitive and selective chemosensor for the determination of palladium(II) cations based on diphenylphosphino derivative of N-aminofluorescein was synthesized. The Pd2+ ion detection is accompanied by a contrast chromogenic “naked-eye” effect of the bright red coloration of an acetonitrile solution and an increase in the fluorescence intensity by 88 times.

Biomineralization of Pd nanoparticles using Phanerochaete chrysosporium as a sustainable approach to turn platinum group metals (PGMs) wastes into catalysts

Due to the increasing demand for recovery of precious metals from waste streams, the role of fungus as a potential adsorbent is growing. Thus, this research aimed to develop a novel method for the biomineralization of palladium nanoparticles using Phanerochaete chrysosporium fungus. The adsorption of palladium onto the fungal mycelium was studied by adding palladium salt at 12–48 ppm to the fermentation medium following the fungal growth. Amide groups of chitin and proteins on the surface of the fungus are believed to coordinate palladium cations yielding Freundlich-type competitive adsorption isotherm. The adsorption capacity was found to reach 22-128 mgPd g−1 of dried fungal biomass. Biomineralization of palladium from an aqueous solution led to the formation of extracellular well defined Pd nanoparticles of 10–14 nm confirmed by XPS, TEM and XRD analyses. The biologically synthesised nanoparticles were found to perform equally well to a Pd/C commercial catalyst in a Heck reaction of styrene and iodobenzene. This is the first reported use of Phanerochaete chrysosporium to synthesise palladium nanoparticles and confirmation of their resulting catalytic activity. The presented example paves the way for the development of fungi-based membranes to be used in the palladium recovery from industrial effluents.

Cation pair formation in copper and palladium exchanged MFI zeolite frameworks - a theoretical study.

The coordination of copper and palladium cations in the channels of MFI frameworks is examined by the QM/MM approach within the ONIOM method. Density functional theory is applied to the high layer of the ONIOM models, and different rings and ring associations are considered with the aim to find the optimal positions for cation pair formation. The Al atoms were located at tetrahedral sites which are known to have high occupancy factors from crystal structure studies. Divalent cations have a strong preference towards six-member ring coordination, and while the energy differences between five-member ring coordination and six-member ring coordination are not that large for the monovalent cations and hydroxyl-cations (M+ and M(OH)+, M = Cu, Pd) they still prefer six-member ring coordination in the straight channel. The monovalent cations form dimers [Pd-Pd]2+ and [Cu-Cu]2+ with bond lengths of 2.50-2.57 Å, but while palladium cations form dimers independent of the Si, Al ordering, the copper cation dimers are stable only with closely positioned negative framework charges. Separation of the two Cu+ cations at distances >4 Å is preferred, unless an oxygen bridge is formed. The cation dimers are exposed in the intersection volume of the straight and sinusoidal channels of MFI, which greatly favors the accessibility of reactants. The oxygen bridged Pd cations accept protons from Brønsted acid sites to form Pd-OH+-Pd and they are able to transfer this proton to reactants: upon co-adsorption of NO and NO2 on Pd-OH+-Pd, protonation of NO2 occurs. In contrast, Cu-OH+-Cu groups reach stabilization by forming hydrogen bonds to framework oxygen atoms. [Pd-Pd] cation dimers alone, or in oxygen-bridged form, provide an energetically favorable route for NO dissociation. Two different configurations with wide and narrow angle ∠MOM were examined for partial oxidation of methane to methanol. The narrow angle [Cu-O-Cu] was found to ease methanol desorption. The active site [Pd-O-Pd] is superior to [Cu-O-Cu], providing lower energy barriers for methane activation and methanol desorption.

Double complex salts [PdL4][RuNO(NO2)4OH] (L = NH3, Py) synthesis, structure and preparation of bimetallic metastable solid solution Pd0.5Ru0.5

Two double complex salts containing [RuNO(NO2)4OH]2− anion and [PdL4]2+ cations (L = NH3, Py) were prepared and described by IR-spectroscopy, single crystal and powder XRD. The crystal structure of both compounds is composed by complex palladium cations and complex ruthenium anions. In case of [Pd(NH3)4][RuNO(NO2)4OH] cations and anions are bounded by hydrogen bonds between NH3 and NO2 ligands. The thermal decomposition of the salts was examined in inert and reductive atmospheres. Both the complexes decompose in several stages, first stage according to IR spectroscopy is comprised with the cleavage of OH group of anion, further decomposition undergoes with the removal on NH3 and NO2 ligands. In case of [Pd(NH3)4][RuNO(NO2)4OH] the final temperature of thermolysis in reductive atmosphere is 250–270 °C and the final product corresponds to metastable Pd0.5Ru0.5 solid solution. The composition of metal solid solution was confirmed by XRD and EDX data. Electrochemical and catalytical properties of prepared solid solutions were examined.

A Rotaxane‐like Cage‐in‐Ring Structural Motif for a Metallosupramolecular Pd6L12 Aggregate

A BODIPY-based bis(3-pyridyl) ligand undergoes self-assembly upon coordination to tetravalent palladium(II) cations to form a Pd6 L12 metallosupramolecular assembly with an unprecedented structural motif that resembles a rotaxane-like cage-in-ring arrangement. In this assembly the ligand adopts two different conformations-a C-shaped one to form a Pd2 L4 cage which is located in the center of a Pd4 L8 ring consisting of ligands in a W-shaped conformation. This assembly is not mechanically interlocked in the sense of catenation but it is stabilized only by attractive π-stacking between the peripheral BODIPY chromophores and the ligands' skeleton as well as attractive van der Waals interactions between the long alkoxy chains. As a result, the co-arrangement of the two components leads to a very efficient space filling. The overall structure can be described as a rotaxane-like assembly with a metallosupramolecular cage forming the axle in a metallosupramolecular ring. This unique structural motif could be characterized via ESI mass spectrometry, NMR spectroscopy, and X-ray crystallography.

Completely Aqueous Route for Metallization of Structural Polymeric Materials in Micro-Electro-Mechanical Systems

Recent developments in the fabrication of micro-electro-mechanical systems (MEMS) are moving away from the deposition/mask/etch paradigm and instead exploiting useful properties of polymers. Many polymeric insulating materials, such as Parylene, PMMA, HSQ, SU-8 and KMPR, have attracted attention in microfabrication lately, because of their low cost and significantly easy processing procedures [1,2]. Metallization of these polymers is required for their integration in MEMS technology. While conventional microfabrication methods for preparing metallic thin films on insulating substrates are limited to vapor deposition techniques, it has recently demonstrated that electroless deposition can be considered as an alternative and efficient approach [3,4]. Presently used process of electroless plating onto plastics requires a pretreatment based on chromic acid etching for oxidizing the surface. This pretreatment increases the surface energy and wettability for the subsequent step of surface activation with noble metal catalysts. Thus, the development of simple, cost-effective and environment friendly strategies, such as avoiding chromic acid etching and/or minimizing the gravimetric use of noble metal, to metallize the surface of insulating substrates is of huge interest. Here, we report a simple one step covalent amination of the surface of commercial structural polymers employing diazonium-based aqueous chemistry. These amine-terminated functionalities allow minimizing the quantity of palladium cations used as catalyst for the subsequent electroless nickel deposition, as well as offer excellent adhesion between the polymer substrate and the nickel film. X-ray photoelectron spectroscopy is carried out to elucidate the mechanism of surface functionalization with amine groups. We then focus our attention on the comprehensive characterization of the metallic thin film through scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy techniques. Keywords: Metallization of plastics, diazonium chemistry, covalent grafting, environment plating process, MEMS fabrication Reference W. Dai et al., Sensors and Actuators A 135 (2007) 300–307.Y. Liu et al., Progress in Polymer Science 52 (2016) 79–106.Y. Shacham-Diamand et al. Microelectron. Eng. 132 (2015) 35–45.G. Zeb et al., Applied Surface Science 407 (2017) 518–525.

Supramolecular Nanotubules as a Catalytic Regulator for Palladium Cations: Applications in Selective Catalysis

AbstractDespite the recent development of highly efficient and stable metal catalysts, conferral of regulatory characteristics to the catalytic reaction in heterogeneous systems remains a challenge. Novel supramolecular nanotubules were prepared by alternative stacking from trimeric macrocycles, which was found to be able to coordinate with Pd cations. The Pd complexes exhibited a high catalytic performance for C−C coupling reaction. Notably, the tubular catalyst was observed to be controlled by supramolecular reversible assembly and showed superior heterogeneous catalytic activity, which was maintained for a number of cycles or reuse under an aerobic environment. Furthermore, the supramolecular catalyst showed unprecedented selectivity for the multifunctional coupling reaction and was able to serve as a new constructor of asymmetrical compounds.

Supramolecular Nanotubules as a Catalytic Regulator for Palladium Cations: Applications in Selective Catalysis.

Despite the recent development of highly efficient and stable metal catalysts, conferral of regulatory characteristics to the catalytic reaction in heterogeneous systems remains a challenge. Novel supramolecular nanotubules were prepared by alternative stacking from trimeric macrocycles, which was found to be able to coordinate with Pd cations. The Pd complexes exhibited a high catalytic performance for C-C coupling reaction. Notably, the tubular catalyst was observed to be controlled by supramolecular reversible assembly and showed superior heterogeneous catalytic activity, which was maintained for a number of cycles or reuse under an aerobic environment. Furthermore, the supramolecular catalyst showed unprecedented selectivity for the multifunctional coupling reaction and was able to serve as a new constructor of asymmetrical compounds.