Pd–Rh Nanocrystals with Tunable Morphologies and Compositions as Efficient Catalysts toward Suzuki Cross-Coupling Reactions

Abstract

Delicate elaboration of the nanostructures of multimetal catalytic materials with well-defined shapes and compositions to reveal their potential use as heterogeneous nanocatalysts for organic synthetic reactions with the combined merits of heterogeneous and homogeneous catalysis is both scientifically and technologically important, but this type of investigation has remained rarely pursued. In this work, we demonstrated a facile hydrothermal approach toward the one-pot shape-selective syntheses of Pd−Rh nanocrystals with tunable compositions and morphologies, including hollow nanocubes (NCs), nanoicosahedrons (NIs), and nanotruncated octahedrons (NTOs), using poly(vinylpyrrolidone) as both reductant and capping agent and halide anions (Br − /I − ) as shape control agents. The formation of Pd−Rh hollow NCs was induced by an iodine adsorbate-induced reconstruction mechanism with KI, whereas the formation of Pd−Rh NIs and NTOs were realized by controlling the selective nucleation of twinned seeds or single crystal seeds and their relative growth rates along different facets (e.g., ( 111) and (100) facets) through finely adjusting the Pd/Rh ratio and the amount of KBr added in the absence of KI. Due to the great significance of Pd-catalyzed organic reactions, the catalytic performances of Pd−Rh nanocrystals for Suzuki cross-coupling reactions with different reactants were evaluated. The measured turnover frequencies (TOFs) suggested that Pd−Rh hollow NCs held considerably enhanced catalytic activities (at least 3 times) than other Pd-based solid nanocrystals including Pd−Rh NIs, Pd−Rh NTOs, Pd−Rh NCs, Pd NCs, and commercial Pd/C, with iodobenzene as the reactant. In addition, even for more inert reactants such as bromobenzene or 4-bromotoluene, the catalytic activities of Pd−Rh hollow NCs were still impressive (showing similar TOFs to those of other shapes for reactions with iodobenzene as the reactant), indicating the promising application of Pd-based nanocatalysts for other powerful Pd-catalyzed organic synthesis reactions. Meanwhile, Pd-based solid NCs, enclosed with (100) facets only, showed better catalytic performance than NIs as well as NTOs, which had a larger fraction of (111) facets other than (100) ones, further suggesting that morphology differences were vitally significant to tune the catalytic performances of bimetallic nanocatalysts.

Evolution of surface of Pd-Rh bimetallic nanocubes and its correlation with CO oxidation

“…S3, the peaks of Pd x Rh 1−x NCs XRD patterns shifted to low angles with the increase of Pd concentration, indicating a lattice expansion due to the incorporation of Pd into Rh. The detail shape-control synthesis mechanism of Pd-Rh NCs by halide ions has been discussed in our previous reports [40][41][42].…”

Ir-Pd nanoalloys with enhanced surface-microstructure-sensitive catalytic activity for oxygen evolution reaction in acidic and alkaline media

“…As the surface enrichment of Ir, the interdiffusion between Ir and Pd takes place. Due to the much faster diffusion rate of Pd, Kirkendall effect in Ir-Pd alloy nanoparticles leads to the hollow structure finally [32,33].…”

Dual Lewis Acidic/Basic Pd0.5Ru0.5–Poly(N‐vinyl‐2‐pyrrolidone) Alloyed Nanoparticle: Outstanding Catalytic Activity and Selectivity in Suzuki–Miyaura Cross‐Coupling Reaction

“…[10] Thus, bimetallica lloyedN Cs are now ah ot research topic from both scientific and technological viewpoints, [11] because the development of highly activea nd selective, and durable noble NCs is vitally important for atomically utilizing the catalysts and the reactants with the maximum product output at low cost and low environment impact in the chemical transformation. [12] However, it is still difficult to synthesize bimetallic alloyed solid-solution NPs of uniformly homogeneous composition with predetermined shape and compositionb yw et chemicalsynthesis because of the variations in the standard reductionp otentialo fi ndividual alloyed metallicc omponent, associated different atomics izes, and reduction rates. [8,13] For example,amiscible solid solution in binary form, e.g.,R u ÀRh, RhÀPd, and RuÀPd,i sv ery difficult to synthesize, [14] although Ru, Rh, andP da re neighboring 4d-series noble metals in the periodic table.…”

“…As the catalytic performance of the NPs catalysti sl argely dependent on the nanostructures,p rocessing technologies, and the intrinsic physical and chemical properties of the constitutive components in the nanostructures, [7b] and the more important possible synergetic catalytic effect in nanocomposite catalysts is prevailed in many nanocomposites mostly synthesized by chemicalp rocesses, [7b, 19d, 21] we first synthesized Pd 0.5 Ru 0.5 -PVP NPs in chemical reduction process [15b] and then characterized the NP surface. After that, NP was tested in SMC reaction with the aim of achieving considerable reduction of both Pd loading and reactiont ime to overcome the current metal-leaching issue [12,22] towardt he development of environmentally benign bifunctional catalysts regarding greener perception,a nd subsequently its catalytic mechanism for CÀCc ross coupling reaction, as bimetallic nanoparticles are expected to reduce the cost of catalysts and improve their resistance to poisoning. [19a] In this article, we, for the first time, focus on the new development of ar obustd ual Lewis acid/base characteristic NC of unsupported PVP-stabilized Pd 0.5 Ru 0.5 solid-solution NPs, which revealed uniformity and homogeneity in composition of both Pd and Ru at the atomicl evel and equallyo pposite charges (both d + and dÀ)o ni ts surface, and showed its bifunctional catalytic activityrevealing high catalytic efficiencyand selectivity with recycle ability in SMC reaction under mild conditions in air withoutstructural change and metal leaching.…”