Amphiphilic Self-Assembly of Nanocrystals at Emulsion Interface Renders Fast and Scalable Quasi-Nanosheet Formation

Scalable assembly of nanocrystals (NCs) into two-dimensional (2D) nanosheets has aroused great interest, yet it remains under-explored. This is because current 2D assembly methods rely mainly on the use of solid- or liquid-air interfaces, which are inherently difficult for upscaling and thus lack practicability. Here, with a microemulsion-based amphiphilic assembly technique, we achieve a fast and scalable preparation of free-standing nanosheets comprising few-layer, tightly packed NCs, namely, quasi-nanosheets (quasi-NSs). Acetic acid, acting as both solvent and surface-treatment agent, is used to render the initially hydrophobic NCs amphiphilic, while simultaneously inducing the interfacial instability right after the assembly of NCs at the emulsion interface to afford quasi-NSs. This amphiphilic assembly method is applicable to a variety of NCs, and multicomponent quasi-NSs are also attainable upon coassembly of different types of NCs. In addition, the structural advantages of quasi-NSs in catalysis are showcased by using NiFe2O4 quasi-NSs as electrocatalysts for the oxygen evolution reaction. This work opens a new route for the scalable construction of 2D NC sheets with designated components and functions.

Room-temperature coalescence of Pd nanoparticles with sacrificial templates and sintering agents, and their catalytic activities in the Suzuki coupling reaction

Porous metal structures are very useful for heterogeneous catalysts in organic syntheses. This study reports a novel method to fabricate porous Pd structures by room-temperature (RT) coalescence of Pd nanoparticles (Pd NPs). First, oleylamine-capped Pd NPs were synthesized, and then Pd NP pastes were fabricated by mixing with tri-n-octylphosphine oxide as a sacrificial template. Finally, the Pd NP paste was dipped into methanol containing a sintering agent. When KOH was used as the sintering agent, porous Pd structures could be successfully obtained at RT. The catalytic activities of porous Pd structures were investigated in the Suzuki coupling reaction and they increased with the increase of the KOH concentration in the sintering process. These results indicate that pre-activation of porous Pd structures by KOH increased the catalytic activities.

Synergistic effect of the Pd–Ni bimetal/carbon nanofiber composite catalyst in Suzuki coupling reaction

A novel Pd₁Ni₄ bimetal nanocomposite catalyst was prepared and showed better performance than their monometallic counterpart. What's more, the catalyst could be reused ten times without significant change in catalytic activity, which met the request of sustainable chemistry.

Interface-Controlled Pd Nanodot-Au Nanoparticle Colloids for Efficient Visible-Light-Induced Photocatalytic Suzuki-Miyaura Coupling Reaction

Plasmonic nanostructures can be employed for performing photocatalytic reactions with visible-light illumination involving two different possible mechanisms, namely, the near-field enhancement and/or direct hot-electron transfer to the conduction band of an active catalyst. In this study, we demonstrate the significant contribution of a graphene interface layer present between plasmonic nanoparticles and active catalysts (Pd nanodots) in enhancing the photocatalytic efficiency of Pd nanodots through an accelerated electron transfer process. The well-defined Pd-nanodot-modified gold nanoparticles with or without a graphene interface layer were prepared using a wet-chemical synthetic method. The role of the graphene interface was investigated by performing wavelength-dependent reduction studies using potassium hexacyanoferrate (III) in the presence of Pd-nanodot-modified cysteamine-modified AuNPs (Pd-cys-AuNPs), Pd-nanodot-modified graphene oxide (GO)-coated AuNPs (Pd-GO-AuNPs), and Pd-nanodot-modified reduced GO (rGO)-coated AuNPs (Pd-rGO-AuNPs). The fastest rate for the reduction of Fe3+ to Fe2+ was obtained with Pd-rGO-AuNPs because of the fast electron transfer achieved in the presence of the reduced graphene oxide layer. The highest catalytic activity for the visible-light induced C-C coupling reaction was obtained with Pd-rGO-AuNPs, indicating the role of the graphene interface layer. These results indicate that the design and use of engineered interfaces are of importance to achieve enhanced catalytic activity with plasmonic hybrid nanomaterials.

Large-scale synthesis of uniformly loaded cobalt nanoparticles on alumina for efficient clean fuel production

The Co/Al₂O₃ nanocatalyst prepared with tens of gram scale in a batch, showed good CO conversion (∼76%), very high CTY value (∼1.4 × 10⁻⁴ mol_CO g_Co⁻¹ s⁻¹) and remarkable hydrocarbon productivity (∼1.0 g_HC g_cat⁻¹ h⁻¹) under controlled FTS conditions.

Robust iron-carbide nanoparticles supported on alumina for sustainable production of gasoline-range hydrocarbons

A robust iron-carbide/alumina catalyst shows excellent catalytic performance for selective production of liquid fuels.

Pd nanoparticles modified rod-like nitrogen-doped ordered mesoporous carbons for effective catalytic hydrodechlorination of chlorophenols

The preparation of rod-like nitrogen-doped ordered mesoporous carbons (NOMCs) through a facial aqueous soft-template self-assembly route in one-pot is presented in this work.

Microwave-assisted route for the preparation of Pd anchored on surfactant functionalized ordered mesoporous carbon and its electrochemical applications

A microwave-assisted route for rapidly synthesizing Pd nanoparticles assembled on sodium dodecyl sulphate (SDS)-functionalized ordered mesoporous carbon (Pd-SOMC) hybrid nanocomposites has been reported.

Palladium nanoparticles embedded in metal–organic framework derived porous carbon: synthesis and application for efficient Suzuki–Miyaura coupling reactions

An efficient Pd catalyst supported on novel nanoporous carbon was developed for the Suzuki-Miyaura coupling reaction. The prepared catalyst can be readily recovered and reused 5 times without significant loss of catalytic activity.

Rose-like Pd-Fe3O4 hybrid nanocomposite-supported Au nanocatalysts for tandem synthesis of 2-phenylindoles

A facile synthesis of rose-like Pd-Fe3O4 nanocomposites via controlled thermal decomposition of Fe(CO)5 and reduction of Pd(OAc)2, followed by the immobilization of Au nanoparticles (NPs) onto the Pd-Fe3O4 supports, is reported. The morphology of these hybrid nanostructures could be easily controlled by varying the amount of Fe(CO)5 and the reaction temperature. Moreover, the synthesized Au/Pd-Fe3O4 catalyst exhibited high catalytic activity for the tandem synthesis of 2-phenylindoles and demonstrated magnetic recyclability.

Mesoporous materials: versatile supports in heterogeneous catalysis for liquid phase catalytic transformations

This review article provides an overview of recently reported liquid phase heterogeneous catalytic reactions performed over mesoporous materials, along with their different synthesis strategies and critical role in environment-friendly green catalysis.

Surfactant-free Pd@pSiO2 yolk–shell nanocatalysts for selective oxidation of primary alcohols to aldehydes

The surfactant-free Pd@pSiO₂ yolk–shell nanoparticles proved to be an efficient catalyst for the oxidation of substituted benzyl alcohols.

Controlled synthesis of uniform palladium nanoparticles on novel micro-porous carbon as a recyclable heterogeneous catalyst for the Heck reaction

Highly dispersed palladium nanoparticles encaged by micro-porous carbon exhibit excellent cycling performance towards the Heck cross-coupling reaction.

Palladium nanoparticles encapsulated inside the pores of a metal–organic framework as a highly active catalyst for carbon–carbon cross-coupling

Palladium nanoparticles were successfully encapsulated in the cages of MIL-101, which exhibited high catalytic activity toward the C–C coupling reactions.

Facile synthesis of Pd/Fe3O4/charcoal bifunctional catalysts with high metal loading for high product yields in Suzuki–Miyaura coupling reactions

Bifunctional Pd/Fe₃O₄/charcoal nanocatalysts are synthesized by simple solid-state grinding. Highly loaded Pd and Fe₃O₄ nanoparticles are observed and exhibit high product time yield for Suzuki–Miyaura coupling reactions.