Supported Pd Nanoparticles Research Articles

Chiral Organic Salt Supported Pd Nanoparticles as Selective Heterogeneous Catalysts of Hydrogenation Reactions

AbstractIn this study, we report the synthesis of a new type of chiral crystalline organic porous salt CF2 derived from the ionic reaction between tetrakis(4‐sulfophenyl)methane (TSPM) and the tetra‐(S)‐prolylamide of tetrakis(4‐aminophenyl)methane, (S)‐TPPM, and its ability to stabilize 2 nm palladium nanoparticles to give a novel, nonpyrophoric, chiral, catalytic material Pd@CF2. The preparation of the catalyst was very simple and conducted in water. The heterogeneous catalytic performance of Pd@CF2 was tested in hydrogen reductions of olefins and substituted nitroaromatic compounds using Pd/C as a comparison to determine the specific features of the novel catalyst. Although both types of catalysts exhibited similar catalytic activity in case of reductions of diphenylacetylene and nitrobenzene, Pd@CF2 predominantly promoted the reduction of p‐nitrobenzaldehyde to p‐aminobenzyl alcohol whereas Pd/C gave p‐toluidine. The reduction of p‐dinitrobenzene led to predominant formation of p‐nitrophenylhydroxylamine if promoted by the novel catalyst and to a mixture of products if promoted by Pd/C. In addition, the introduction of p‐alkoxy groups onto nitrobenzenes slowed down the reduction with Pd@CF2 but had no influence on Pd/C activity. A hypothesis ascribing these observations to dissimilar equilibrium distributions of nitro and polar groups within the organic framework and the palladium metal surface is proposed to rationalize the selectivity of the novel catalytic material.

Facile Fabrication of LaFeO 3 Supported Pd Nanoparticles as Highly Effective Heterogeneous Catalyst for Suzuki–Miyaura Coupling Reaction

Supported Pd catalysts have been widely studied due to their enormous potential as candidates for heterogeneous Suzuki–Miyaura coupling reactions. However, the sintering and low activity of active sites still remain challenges. A vesicle‐shaped LaFeO3‐supported Pd catalyst (I‐Pd/LaFeO3) was successfully fabricated using the impregnation method and tested for the Suzuki–Miyaura coupling reaction. Compared to P‐Pd/LaFeO3 prepared with photo‐deposition and Pd/Al2O3 prepared with impregnation, the I‐Pd/LaFeO3 catalyst exhibits significantly higher catalytic activity, stability, and reusability. The chemical composition and electron states of different Pd‐based catalysts were well studied based on various characterizations and the results indicated that the excellent performance of I‐Pd/LaFeO3 can be attributed to its unique nanostructure and the strong interactions between LaFeO3 and palladium nanoparticles. The impregnation method and the choice of the LaFeO3 support show a great influence on the electronic properties of Pd species, their reducibility, and, consequently, their reaction behavior. This unique LaFeO3 supported Pd catalyst provided an environmentally friendly heterogeneous method for the Suzuki–Miyaura coupling reaction.

Layered silicate PLS-3 with PREFER structure supported Pd nanoparticles: A recyclable catalyst for the synthesis of furfuryl ethyl ether

Supported Pd catalysts has found wide applications in reductive etherification of aldehydes. However, the synthesis of furfural-derived ethers on Pd catalysts has encountered great challenges because several side reactions such as over-hydrogenation of furan ring and decarbonylation always occur simultaneously under the reaction conditions. We herein reported the catalytic performance of Pd nanoparticles (∼4 nm) supported on the external surface of layered structured PLS-3 zeolite with narrow pore size (<0.4 nm) and large external surface area (80–100 m2/g). The PLS-3 with Si/Al of 92 having total acid sites of 93 μmol/g showed satisfied ether selectivity. Pd nanoparticles located on the external surface showed better etherification selectivity than those confined in the framework, due to the less diffusion limitation of furfural acetal as an intermediate.

CO-Induced Dynamic Behavior of Al2O3-Supported Pd Nanoparticles at Room Temperature

CO-Induced Dynamic Behavior of Al₂O₃-Supported Pd Nanoparticles at Room Temperature

Pd nanoparticles on functionalized carbon nanotubes for enhanced formic acid hydrogen production under ambient conditions

Herein, carbon nanotubes (CNTs) are acidified and M (M = B or N) doped to support Pd nanoparticles (PdNPs) for upgrading to Pd/MCNT catalysts used in H2 production from formic acid (FA). The characterization analysis demonstrates the support composition affects the electronic properties and size of PdNPs, thus impacting the performance of Pd/MCNTs. Among the assessed materials, Pd/BCNTs exhibit the largest specific surface area (128.1273 m2g−1) and smallest PdNPs particle size (6.28 nm). These properties result in significant improvements in FA conversion (41.67 %), and turnover frequency value (3451 h−1) compared to conventional Pd/CNTs (17.36 % and 564 h−1, respectively). The study evaluates the service life and repeatability of Pd/BCNTs and analyzes the catalyst mechanism. This study filled the vacancy of acidification-modified and doped CNTs in Pd regulation, enhanced Pd's catalytic performance, and further supported FA as an H2 storage material.

CTAB-assisted synthesis of reduced graphene oxide supported Pd nanoparticles (Pd@rGO) as a sustainable heterogeneous catalyst for C-2 arylation of indoles with arylboronic acids

A series of Pd nanoparticles (NPs) incorporated in reduced graphene oxide (rGO), viz. Pd@rGO0.16, Pd@rGO0.32, Pd@rGO0.48, and Pd@rGO1 were synthesized employing water as a solvent. The subscript values correspond to the millimoles of cetyltrimethylammonium bromide (CTAB) utilized in the synthesis process. The quantity of CTAB was varied to finely tune both the morphology and size of the resulting nanoclusters. Transmission Electron Microscopy (TEM) analysis indicated that the average particle sizes of Pd@rGO0.16 and Pd@rGO0.32 fall in the range of 4.5–5.0 nm and 20–25 nm, respectively. On the other hand, particles were found to be agglomerated in Pd@rGO0.48 and Pd@rGO1. The Pd@rGO0.16 composite was exhaustively characterized by TEM, Scanning Electron Microcopy-Energy Dispersive X-ray analysis (SEM-EDX), powder X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements. ICP-AES analysis of Pd@rGO0.16 indicated that 0.01 g of Pd@rGO0.16 contains 0.09 mol% Pd. The catalytic potentiality of these NPs was investigated for direct C(sp[1])-H bond activation of various indoles with aryl boronic acids. Among the four composites, Pd@rGO0.16 exhibited the best activity for the abovementioned organic transformation. Different indoles with diverse electronic groups underwent coupling with aryl boronic acids giving up to 86 % product yield. It was retrievable for up to five consecutive catalytic cycles without compromising its catalytic activity.

N, O Co‐Doping Enhanced Adsorption of Chloramphenicol for Highly Efficient and Robust Electrocatalytic Hydrodechlorination

Comprehensive SummaryElectrocatalysis technology can effectively promote the hydrodechlorination of chloramphenicol (CAP) to reduce the bio‐toxicity. However, there are still some challenges such as low degradation rate and poor stability. Here, we prepared porous N, O co‐doped carbon supported Pd nanoparticles composites (Pd NPs/NO‐C) for electrocatalytic degradation of CAP. The doping of N and O not only effectively enhanced the interaction between substrate and CAP, promoting the mass transfer process, but also enhanced the anchoring effect on Pd nanoparticles, avoiding the occurrence of aggregation. The prepared composites achieved removal efficiency of CAP over 99% within 1 h, and the rate constant was as high as 6.72 h–1, outperforming previous reported electrocatalysts. Additionally, Pd NPs/NO‐C composites showed a wide range of pH tolerance, excellent ion interference resistance and long‐term stability. Our work unravels the importance of mass transfer processes in solution to electrocatalytic hydrodechlorination and provides new research ideas for catalysts design.

Stable Diamine Functionalized Graphene Supported Pd Nanoparticles Showing Excellent Catalytic Activity For Mizoroki–Heck Coupling Reactions

AbstractWe used a simple technique to create palladium nanoparticles on diamine functionalised graphene (Pd(0)‐AAPTMS@G) with an average particle size of 5.5 nm. Our earlier research described the Pd(0)‐AAPTMS@G material as an effective catalyst with outstanding conversion and yields for the Suzuki coupling reaction. We reported the characterisation data for Pd(0)‐AAPTMS@G catalysts previously. Here, we provide a narrative for the excellent selectivity and high yields (92–100 %) for the Mizoroki–Heck coupling product over the same Pd(0)‐AAPTMS@G catalyst. Six uses of the generated catalyst are possible without any activity loss. We also compared the catalyst characterisation for both fresh and reused catalysts.

Effect of zeolites on the alkylation of aromatics with alkanes using a Pd nanoparticle/solid acid cooperative catalytic system

The direct alkylation of benzene with alkanes is an effective method for alkylbenzene production. Our group previously discovered that a mixture of supported Pd nanoparticles and solid acids effectively promoted the alkylation of benzene with alkanes. Herein, the alkylation of toluene with n-heptane was catalyzed by physical mixture of H-mordenite and Pd nanoparticles supported on hydrotalcite to afford the corresponding C7 alkylation product with 87% selectivity and 14% toluene conversion. The reaction slightly proceeded in the absence of Pd nanoparticles or H-mordenite, indicating cooperative catalysis by the two different solid catalysts. Moreover, the high stability of the Pd nanoparticles on hydrotalcite was confirmed via reuse experiments and transmission electron microscopy (TEM) analysis. The catalyst mixture was reused at least three times without any loss of product yield, and after three reuses, TEM analysis revealed that the size of the Pd nanoparticles following the initial catalytic reaction was similar to that of the catalyst. Scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS) analysis of the recovered catalyst mixture revealed the preservation of Pd nanoparticles on the hydrotalcite surface, as well as the close positioning of the two different catalyst particles, thus suggesting interparticle hydrogen transfer. The structure of the solid acid strongly affected the alkylation product selectivity. For example, H-mordenite showed high selectivity for the n-heptane alkylation product with a C7 alkyl chain, whereas the selectivity changed with other zeolites. This cooperative catalytic system can be applied to the alkylation of other substituted benzenes, such as xylenes and phenols, with good selectivity toward the desired alkylation product.

Recent Advancements in Continuous-Flow Suzuki-Miyaura Coupling Utilizing Immobilized Molecular Palladium Complexes.

Immobilized Pd-catalyzed Suzuki-Miyaura coupling under continuous-flow conditions using a packed-bed reactor, representing an efficient, automated, practical, and safe technology compared to conventional batch-type reactions. The core objective of this study is the development of an active and durable catalyst. In contrast to supported Pd nanoparticles, the attachment of Pd complexes onto solid supports through well-defined coordination sites is considered a favorable approach for preparing highly dispersed and stabilized Pd species. These species can be directly employed in various flow reactions without the need for pre-treatment. This concept paper explores recent achievements involving the application of immobilized Pd complexes as precatalysts for continuous-flow Suzuki-Miyaura coupling. Our focus is to elucidate the significance of the designed catalyst structures in relation to their catalytic performance under flow conditions. Additionally, we highlight various reaction systems and catalyst packing methods, emphasizing their crucial roles in establishing a practical synthesis process.

Highly active polyethylene glycol grafted cellulose supported Pd nanoparticles for glucose electrooxidation

In this study, poly(ethylene glycol) (PEG) grafted cellulose (CE) composite catalyst support material (PEG-CE) was obtained by chemically cross-linking PEG at varying molecular weight and CE with isophorone diisocyanate (IPDI) and 2,4-toluylene diisocyanate (TDI). PEG-CE supported Pd (Pd/PEG-CE) catalyst was prepared by the chemical reduction method. The crystal size of the Pd/PEG-CE catalyst is 4.79 nm and its crystal structure has been determined to be face-centered cubic Pd. Elemental mapping results indicate that Pd was reduced onto PEG-CE successfully and uniformly. Pd exists in the elemental and Pd-O form in the catalyst system. The Pd loading rate of Pd/PEG-C_IPDI catalyst was determined as 18.8% by mass. Among the PEG-CEs prepared with TDI and IPDI, PEG4000-CE_TDI and PEG6000-CE_IPDI displayed the highest specific activities of 1.03 and 1.50 mA cm−2 for glucose electrooxidation. With Pd reduction on PEG4000-CE_TDI and PEG6000-CE_IPDI, the specific activities increased to 1.62 mA cm−2 and 6.97 mA cm‐2. Pd/PEG6000-CE_IPDI has the highest electrocatalytic activity and stability in this study for glucose electrooxidation and is an encouraging anode catalyst for direct glucose fuel cells.

Local coordination and electronic interactions of Pd/MXene via dual‐atom codoping with superior durability for efficient electrocatalytic ethanol oxidation

AbstractCatalyst design relies heavily on electronic metal‐support interactions, but the metal‐support interface with an uncontrollable electronic or coordination environment makes it challenging. Herein, we outline a promising approach for the rational design of catalysts involving heteroatoms as anchors for Pd nanoparticles for ethanol oxidation reaction (EOR) catalysis. The doped B and N atoms from dimethylamine borane (DB) occupy the position of the Ti3C2 lattice to anchor the supported Pd nanoparticles. The electrons transfer from the support to B atoms, and then to the metal Pd to form a stable electronic center. A strong electronic interaction can be produced and the d‐band center can be shifted down, driving Pd into the dominant metallic state and making Pd nanoparticles deposit uniformly on the support. As‐obtained Pd/DB–Ti3C2 exhibits superior durability to its counterpart (∼14.6% retention) with 91.1% retention after 2000 cycles, placing it among the top single metal anodic catalysts. Further, in situ Raman and density functional theory computations confirm that Pd/DB–Ti3C2 is capable of dehydrogenating ethanol at low reaction energies.

Biosynthesis Parameters Control the Physicochemical and Catalytic Properties of Microbially Supported Pd Nanoparticles.

The biosynthesis of Pd nanoparticles supported on microorganisms (bio-Pd) is achieved via the enzymatic reduction of Pd(II) to Pd(0) under ambient conditions using inexpensive buffers and electron donors, like organic acids or hydrogen. Sustainable bio-Pd catalysts are effective for C-C coupling and hydrogenation reactions, but their industrial application is limited by challenges in controlling nanoparticle properties. Here, using the metal-reducing bacterium Geobacter sulfurreducens, it is demonstrated that synthesizing bio-Pd under different Pd loadings and utilizing different electron donors (acetate, formate, hydrogen, no e- donor) influences key properties such as nanoparticle size, Pd(II):Pd(0) ratio, and cellular location. Controlling nanoparticle size and location controls the activity of bio-Pd for the reduction of 4-nitrophenol, whereas high Pd loading on cells synthesizes bio-Pd with high activity, comparable to commercial Pd/C, for Suzuki-Miyaura coupling reactions. Additionally, the study demonstrates the novel synthesis of microbially-supported ≈2nm PdO nanoparticles due to the hydrolysis of biosorbed Pd(II) in bicarbonate buffer. Bio-PdO nanoparticles show superior activity in 4-nitrophenol reduction compared to commercial Pd/C catalysts. Overall, controlling biosynthesis parameters, such as electron donor, metal loading, and solution chemistry, enables tailoring of bio-Pd physicochemical and catalytic properties.

Construction of MOF-5 derived ZnO composites porous carbon supported Pd nanoparticles as highly stable catalyst for methanol and ethanol oxidation

The preparation of highly active and stable Pd-based catalysts for direct alcohol fuel cells (DAFC) is hampered by inefficient utilization of the active sites, susceptibility to CO poisoning, poor stability, and relatively slow reaction kinetics. Herein, the stability and anti-toxicity of the catalysts (Pd/ZnO/MDC) are tuned by loading Pd nanoparticles on the carbon-coated ZnO support, achieving efficient electrocatalysis for methanol and ethanol oxidation reaction (MOR and EOR). TEM result shows the ZnO is covered by the carbon layer formed outside of MOF-5 derived porous carbon, which can prevent it from dissolving under harsh conditions. The mass activities of the well-tuned catalyst Pd/ZnO/MDC(800) for MOR and EOR are 931.83 mA/mg and 1838.30 mA/mg, respectively. It is due to the improved electron transport efficiency between the Pd and ZnO, and the enhanced stability by carbon layer outside the ZnO. It is also found that the onset potential and the peak potential of Pd/ZnO/MDC(800) (−0.813 V, −0.228 V) in CO stripping experiment in MOR are more negative than Pd/MDC(800) (−0.261 V, −0.215 V). This result indicates that the existence of ZnO helps to provide surface hydroxyl group, which promotes the oxidation of the intermediates. This work indicates provides a feasible idea for DAFC catalyst design and construction.

Carboxyl-Decorated UiO-66 Supporting Pd Nanoparticles for Efficient Room-Temperature Hydrodeoxygenation of Lignin Derivatives.

Hydrodeoxygenation (HDO) of lignin derivatives at room-temperature (RT) is still of challenge due to the lack of satisfactory activity reported in previous literature. Here, it is successfully designed a Pd/UiO-66-(COOH)2 catalyst by using UiO-66-(COOH)2 as the support with uncoordinated carboxyl groups. This catalyst, featuring a moderate Pd loading, exhibited exceptional activity in RT HDO of vanillin (VAN, a typical model lignin derivative) to 2-methoxyl-4-methylpheonol (MMP), and >99% VAN conversion with >99% MMP yield is achieved, which is the first metal-organic framework (MOF)-based catalyst realizing the goal of RT HDO of lignin derivatives, surpassing previous reports in the literature. Detailed investigations reveal a linear relationship between the amount of uncoordinated carboxyl group and MMP yield. These uncoordinated carboxyl groups accelerate the conversion of intermediate such as vanillyl alcohol (VAL), ultimately leading to a higher yield of MMP over Pd/UiO-66-(COOH)2 catalyst. Furthermore, Pd/UiO-66-(COOH)2 catalyst also exhibits exceptional reusability and excellent substrate generality, highlighting its promising potential for further biomass utilization.

Co‑MOF-Derived Flake-Like Co3O4 Supported Pd Nanoparticles as High-Performance Hydrogen Peroxide Electroreduction Catalysts

Development of highly efficient catalysts for the hydrogen peroxide reduction reaction (HPRR) has been a focus of research for fuel cells using hydrogen peroxide (H2O2) as an alternative cathode oxidant. The carbon-doped flake-like cobalt oxide electrode (Co3O4@C NF) was prepared on nickel foam (NF) by annealing the metal organic framework (MOF). A Co3O4@C/Pd NF (CPNF) electrode was derived from Co3O4@C NF by supporting Pd nanoparticles. Half-cell tests demonstrated that the CPNF electrode exhibited outstanding catalytic performance. The CPNF electrode displayed a high current density of 932 mA cm−2 at −0.8 V (vs Ag/AgCl). This aligns with its low activation energy (7392.8 J mol−1). The electron transfer numbers for the Co3O4@C NF and CPNF electrodes were 2.97 and 3.32, respectively. Incorporating CPNF as the cathode of Direct borohydride-hydrogen peroxide fuel cell (DBHPFC) yielded notable catalytic performance, with a peak power density of 68 mW cm−2. The CPNF electrode exhibited remarkable stability, sustaining continuous current discharge for over 20 h. These electrochemical properties result from the structural characteristics obtained through MOF annealing, which increases the number of exposed active sites and enhances ion transport. Therefore, CPNF stands as a promising cathode catalyst for DBHPFC.

Room temperature synthesis of β-ketonitriles catalyzed by metal–organic framework supported Pd nanoparticles

A Pd supported on a metal–organic framework catalyst has been prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray techniques. The designed heterogeneous catalyst Nd-MOF/Pd can promote the addition reaction of aryl boronic acids with dinitriles to give the corresponding β-ketonitriles in high yields at room temperature. Moreover, the catalyst can be recovered and recycled, running for five times without obvious loss of its reactivity.

Multi-functional imidazolium dendrimers based on thiacalix[4]arenes: self-assembly, catalysis and DNA binding.

For the first time, dendrimers based on thiacalix[4]arenes bearing imidazolium dendrons on one side and alkyl fragments on another side of the macrocyclic platform and symmetrical dendrimers with four dendrons on both sides were synthesized. Dendrons consist of gallic acid-based branches functionalized with imidazolium and triazolium groups. The physicochemical properties of the dendrimers such as micellar concentration (CMC), size, and solubilization capacity were measured. Novel dendrimers exhibit high binding efficiency with calf thymus DNA (ctDNA) as revealed by fluorescence quenching of the DNA-EtBr complex in the presence of macrocycles. Dendrimers have been used as supports for Pd nanoparticles, which show high catalytic activity for the reduction of nitroaromatic compounds.

Tuning the electronic structure of Pd by the surface configuration of Al2O3 for hydrogenation reactions.

The electronic interaction between a metal and a support modulates the electronic structures of supported metals and plays an important role in manipulating their catalytic performance. However, this interaction is mainly realized in heterogeneous catalysts composed of reducible oxides. Herein, we demonstrate the electronic interaction between γ-Al2O3 and η-Al2O3 with varying acid-base properties and supported Pd nanoparticles (NPs) of 2 nm in size. The strength and number of acid-base sites on the supports and catalysts were systemically characterized by FT-IR spectroscopy and TPD. The supported Pd NPs exhibit electron-rich surface properties by receiving electrons from the electron-donating basic sites on γ-Al2O3, which are beneficial for catalyzing the hydrogenation of nitrobenzene. In contrast, Pd NPs loaded on η-Al2O3 are electron-deficient because of the rich electron-withdrawing acid sites of η-Al2O3. As a result, Pd/η-Al2O3 exhibits higher catalytic activity in phenylacetylene hydrogenation than Pd/γ-Al2O3. Our results suggest a promising route for designing high-performance catalysts by adjusting the acid-base properties of Al2O3 supports to maneuver the electronic structures of metals.

Construction of Pd–TiOx interfaces for selective hydrodeoxygenation of CO bonds in vanillin by supporting Pd nanoparticles on ETS-10 zeolite

Pd nanoparticles on ETS-10 zeolite with abundant Pd–TiOx interfaces are very active for the selective hydrodeoxygenation of CO bonds in vanillin.