Atomic control of active-site ensembles in ordered alloys to enhance hydrogenation selectivity

Dasgupta, Anish; He, Haoran; Gong, Rushi; Shang, Shun‐Li; Zimmerer, Eric; Meyer, Randall J.; Liu, Zhe; Janik, Michael J.; Rioux, Robert M.

doi:10.1038/s41557-021-00855-3

Cited by 57 publications

(46 citation statements)

References 42 publications

(39 reference statements)

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“…Many transition metal-based catalysts have been developed for the semihydrogenation reaction. − In particular, gold-based nanomaterials are promising catalysts for the semihydrogenation of alkynes to alkenes due to their high selectivity under relatively mild conditions. − In addition to gaseous dihydrogen, bench-stable hydrogen sources have also been used in the semihydrogenation of alkynes as a safe and convenient method to prepare functional alkenes on the laboratory scale at ambient pressure . One of the major challenges in catalysis is to identify and control the active sites of the catalysts. − Atomically precise gold nanoclusters with well-defined structures have emerged as a new class of model catalysts that allow the identification of the active sites and help the elucidation of catalytic mechanisms. − However, precise control of the catalytic active sites for specific reactions, which underlies enzyme catalysis, is challenging to achieve synthetically. Especially for hydrogenation reactions catalyzed by gold-based nanomaterials, the identification of the active sites is often not possible because of the difficulties in capturing gold hydride intermediates. − Gold hydrides that feature a hydridic hydrogen (H – ) have been proposed as reactive intermediates in hydrogenation reactions involving gold-based nanomaterials; however, prior clusters have featured metallic hydrogens (H • ), − while the identification of hydridic hydrogen has been limited to mononuclear gold complexes. − …”

Section: Introductionmentioning

confidence: 99%

Selective Semihydrogenation of Polarized Alkynes by a Gold Hydride Nanocluster

et al. 2022

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The hydridic hydrogen in nanogold catalysts has long been postulated as an important intermediate in hydrogenation reactions, but it has not been directly observed. Here, we report the synthesis of a new undecagold cluster with a bidentate phosphine ligand. The chelating effects of the bidentate ligand result in a more symmetric Au 11 core with two labile Cl − ligands that can exchange with BH 4 − , leading to a novel undecagold hydride cluster. The new hydride cluster is discovered to readily undergo hydroauration reaction with alkynes containing electronwithdrawing groups, forming key gold-alkenyl semihydrogenation intermediates, which can be efficiently and selectively converted to Z-alkenes under acidic conditions. All key reaction intermediates are isolated and characterized, providing atomic-level insights into the active sites and mechanisms of semihydrogenation reactions catalyzed by gold-based nanomaterials. The hydridic hydrogen in the undecagold cluster is found to be the key to prevent over hydrogenation of alkenes to alkanes. The current study provides fundamental insights into hydrogenation chemistry enabled by gold-based nanomaterials and may lead to the development of efficient catalysts for selective semihydrogenation or functionalization of alkynes.

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Section: Introductionmentioning

confidence: 99%

Selective Semihydrogenation of Polarized Alkynes by a Gold Hydride Nanocluster

et al. 2022

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“…Bimetallic catalysts, consisting of a platinum-group metal and a late-transition metal, featured geometrical variation and electronic redistribution via metal–metal interactions and enhanced the activity and/or selectivity, strongly depending on the crystal-phase and the particle size 1 – 9 . PdCu nanoparticles in the chemically ordered body-centered cubic (B2) phase, for instance, showed pronouncedly increased activity (2–20 times) for the electro-conversion of energy-related molecules 10 – 15 and substantially promoted selectivity for the hydrogenation of multiple carbon–carbon bonds 16 , relative to the disordered face-centered cubic (fcc) ones.…”

Section: Introductionmentioning

confidence: 99%

Tuning crystal-phase of bimetallic single-nanoparticle for catalytic hydrogenation

Liu

et al. 2022

Nat Commun

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Bimetallic nanoparticles afford geometric variation and electron redistribution via strong metal-metal interactions that substantially promote the activity and selectivity in catalysis. Quantitatively describing the atomic configuration of the catalytically active sites, however, is experimentally challenged by the averaging ensemble effect that is caused by the interplay between particle size and crystal-phase at elevated temperatures and under reactive gases. Here, we report that the intrinsic activity of the body-centered cubic PdCu nanoparticle, for acetylene hydrogenation, is one order of magnitude greater than that of the face-centered cubic one. This finding is based on precisely identifying the atomic structures of the active sites over the same-sized but crystal-phase-varied single-particles. The densely-populated Pd-Cu bond on the chemically ordered nanoparticle possesses isolated Pd site with a lower coordination number and a high-lying valence d-band center, and thus greatly expedites the dissociation of H2 over Pd atom and efficiently accommodates the activated H atoms on the particle top/subsurfaces.

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“…Site isolation of the noble metal combined with its electronic modification through alloy formation is crucial toward achieving reaction selectivity. − Dilute alloys of active noble metals (Pd, Pt, Rh) embedded within a more inert matrix (Cu, Ag, Au) have shown excellent chemoselectivity for the semihydrogenation of alkynes and dienes. − In most cases, the selectivity stems from a significantly weaker adsorption of the semihydrogenated product on the isolated atom site compared to a larger ensemble, leading to fast product desorption and suppression of overhydrogenation. Intermetallic alloy surfaces have also been leveraged to a similar effect to enforce site isolation of an active metal within a more inert matrix. − …”

Section: New Catalyst Designsmentioning

confidence: 99%

Haptophilicity and Substrate-Directed Reactivity in Diastereoselective Heterogeneous Hydrogenation

et al. 2022

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Stereoselectivity in heterogeneous hydrogenation of olefins and arenes is typically dictated by the steric properties of the organic substrate, and the inherent steric preference is difficult to alter through the modification of the catalyst or experimental parameters. One strategy to access counter-steric selectivity is to incorporate a stereochemically defined functional group into the substrate that can adsorb to the catalyst surface and “direct” hydrogen addition from the same face. This Perspective provides an overview of heterogeneous directed hydrogenation and elucidates a few design rules about directing group identity, substrate structure, and catalyst composition that lead to diastereoselective reactivity. Monometallic heterogeneous catalysts are capable of diastereoselective directed hydrogenation with only a limited set of substrate scaffolds and directing functional groups. In a given substrate, the complex interplay between directing group conformation, steric bulk, and adsorption strength makes it difficult to predict whether steric or electronic factors will dominate the diastereoselectivity. We then discuss more recent examples of bimetallic catalysts for this reaction and look toward opportunities for bimetallic structures to yield more tunable and general heterogeneous directed hydrogenation catalysts.

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Atomic control of active-site ensembles in ordered alloys to enhance hydrogenation selectivity

Cited by 57 publications

References 42 publications

Selective Semihydrogenation of Polarized Alkynes by a Gold Hydride Nanocluster

Selective Semihydrogenation of Polarized Alkynes by a Gold Hydride Nanocluster

Tuning crystal-phase of bimetallic single-nanoparticle for catalytic hydrogenation

Haptophilicity and Substrate-Directed Reactivity in Diastereoselective Heterogeneous Hydrogenation

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