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Journal ArticleDOI: 10.1021/JACS.1C00578

Impregnating Subnanometer Metallic Nanocatalysts into Self-Pillared Zeolite Nanosheets.

04 Mar 2021-Journal of the American Chemical Society (American Chemical Society (ACS))-Vol. 143, Iss: 18, pp 6905-6914
Abstract: Impregnation is the most commonly used approach to prepare supported metal catalysts in industry. However, this method suffers from the formation of large metal particles with uneven dispersion, poor thermal stability, and thus unsatisfied catalytic performance. Here, we demonstrate that the self-pillared MFI zeolite (silicalite-1 and ZSM-5) nanosheets with larger surface area and abundant Si-OH groups are ideal supports to immobilize ultrasmall monometallic (e.g., Rh and Ru) and various bimetallic clusters via simple incipient wetness impregnation method. The loaded subnanometric metal clusters are uniformly dispersed within sinusoidal five-membered rings of MFI and remain stable at high temperatures. The Rh/SP-S-1 is highly efficient in ammonia borane (AB) hydrolysis, showing a TOF value of 430 molH2 molRh-1 min-1 at 298 K, which is more than 6-fold improvement over that of nanosized zeolite-supported Rh catalyst and even comparable with that of zeolite-supported Rh single-atom catalyst. Because of the synergistic effect between bimetallic Rh-Ru clusters and zeolite acidity, the H2 generation rate from AB hydrolysis over Rh0.8Ru0.2/SP-ZSM-5-100 reaches up to 1006 molH2 molmetal-1 min-1 at 298 K, and also shows record activities in cascade hydrogenation of various nitroarenes by coupling with the hydrolysis of AB. This work demonstrates that zeolite nanosheets are excellent supports to anchor diverse ultrasmall metallic species via the simple impregnation method, and the obtained nanocatalysts can be applied in various industrially important catalytic reactions.

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Topics: Incipient wetness impregnation (59%), Nanomaterial-based catalyst (54%), Ammonia borane (51%) ... read more

11 results found

Journal ArticleDOI: 10.1002/ADMA.202104442
Qiming Sun1, Wang Ning2, Jihong Yu1, Jihong Yu3Institutions (3)
05 Oct 2021-Advanced Materials
Abstract: Zeolites possessing large specific surface areas, ordered micropores, and adjustable acidity/basicity have emerged as ideal supports to immobilize metal species with small sizes and high dispersities. In recent years, the zeolite-supported metal catalysts have been widely used in diverse catalytic processes, showing excellent activity, superior thermal/hydrothermal stability, and unique shape-selectivity. In this review, a comprehensive summary of the state-of-the-art achievements in catalytic applications of zeolite-supported metal catalysts are presented for important heterogeneous catalytic processes in the last five years, mainly including 1) the hydrogenation reactions (e.g., CO/CO2 hydrogenation, hydrogenation of unsaturated compounds, and hydrogenation of nitrogenous compounds); 2) dehydrogenation reactions (e.g., alkane dehydrogenation and dehydrogenation of chemical hydrogen storage materials); 3) oxidation reactions (e.g., CO oxidation, methane oxidation, and alkene epoxidation); and 4) other reactions (e.g., hydroisomerization reaction and selective catalytic reduction of NOx with ammonia reaction). Finally, some current limitations and future perspectives on the challenge and opportunity for this subject are pointed out. It is believed that this review will inspire more innovative research on the synthesis and catalysis of zeolite-supported metal catalysts and promote their future developments to meet the emerging demands for practical applications.

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Topics: Nanomaterial-based catalyst (59%), Dehydrogenation (59%), Catalysis (57%) ... read more

Journal ArticleDOI: 10.1002/ASIA.202100728
Li Chengyang1, Peng Sun1, Fuwei Li1Institutions (1)
Abstract: The confinement of metal species within hierarchical zeolites combines the acidic/basic sites of zeolites, the enhanced mass transfer of mesoporous system, and the inside active metal sites, leading to high activity, unique selectivity, and superior stability in chemicals synthesis, energy and environment catalysis. To date, review on this emerging topic is rarely reported. Herein, we classify five metals-hierarchical zeolites composite (metal@hierarchical zeolites) according to the location of metals on hierarchical structure, including metals located on micropores, intercrystalline mesopores, intracrystalline mesopores, hollow nanobox and mesoporous shells. The synthesis and catalysis applications of metal@hierarchical zeolites composite are provided, highlighting the rational design of catalyst preparation, the improved catalytic efficiency and stability of metal species. Finally, we discuss the current limitations and future opportunities for this emerging field. This Review is expected to inspire more developments and applications of metal@hierarchical zeolites.

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Journal ArticleDOI: 10.1016/J.CEJ.2021.132925
Zuqiao Ou1, Yanzhi Li1, Wenche Wu1, Yunfei Bi2  +3 moreInstitutions (2)
Abstract: Subnanometric metal clusters encapsulated within zeolites are of great interests for the industrial catalysis. Herein we review for the first time the encapsulation of subnanometric metal clusters in zeolites. The concepts of both subnanometric metal clusters and zeolites are briefly introduced. The recent advancements of synthesis methods, such as impregnation, ion-exchange followed by post-treatment, template-guidance approach, in situ hydrothermal synthesis and interzeolite transformation are summarized. Further, the encapsulation effects including metal loading, ligand property, zeolite type and calcination condition for subdividing subnanometric metal clusters and nanoparticles in zeolites using quite similar synthesis procedures during in situ hydrothermal synthesis are firstly reviewed to explore the underlying mechanism. The important catalytic applications mainly contained propane dehydrogenation, formic acid decomposition, ammonia borane hydrolysis, cyclohexane oxidation, water–gas shift reaction and hydrogenation reaction are demonstrated. This review concludes with the challenges and status of both the stability issue under high temperature and advanced characterization techniques as well as the industrial perspectives.

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Topics: Catalysis (50%)

Open accessJournal ArticleDOI: 10.1021/ACSAMI.1C18403
Mei Li1, Shengbo Zhang2, Jiankang Zhao3, Hua Wang1Institutions (3)
Abstract: Catalytic hydrolysis of ammonia borane (AB) provides an effective way to generate pure H2 at ambient temperature for fuel cells. Pt-based catalysts usually exhibit great initial activity toward this reaction but deactivate quickly. Here, we report that the metal-support interactions in Pt/Co3O4 nanocages can simultaneously accelerate the H2 generation and enhance the catalyst's stability. The Pt/Co3O4 catalyst is made for the first time by embedding Pt clusters (∼1.2 nm) in a high-surface-area Co3O4 nanocage to maximize the metal-support interface. The turnover frequency of the Pt/Co3O4 catalyst is about nine times higher than that of commercial Pt/C and outperforms almost all other Pt-based catalysts. X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, in situ spectroscopy, and density functional theory calculations suggest that the Co3O4 nanocages with rich oxygen vacancies facilitate the adsorption and dissociation of H2O to give electropositive H (Hδ+), while the in situ embedded Pt clusters can accelerate the formation of electronegative H (Hδ-) from AB. Subsequently, the Hδ+ and Hδ- spill over to the abundant interfacial sites and bond into H2. In addition to this dual-function synergy effect, the strong metal-support electronic interactions between Co3O4 and Pt benefit the desorption of poisonous B-containing byproducts from Pt sites. This effect together with cluster anchoring leads to a fivefold enhancement in durability compared to commercial Pt/C. The metal-support interactions revealed in this study provide more options for catalyst design toward facile H2 production from chemical hydrogen storage materials.

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Topics: Nanocages (56%), Ammonia borane (52%), Catalysis (52%) ... read more


47 results found

Journal ArticleDOI: 10.1021/AR300361M
Xiaofeng Yang1, Aiqin Wang1, Botao Qiao1, Jun Li2  +3 moreInstitutions (3)
Abstract: Supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in determining the performance of such catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixture of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequent...

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Topics: Heterogeneous catalysis (51%)

2,136 Citations

Journal ArticleDOI: 10.1038/NATURE08288
Minkee Choi1, Kyungsu Na1, Jeongnam Kim2, Jeongnam Kim1  +6 moreInstitutions (4)
10 Sep 2009-Nature
Abstract: Zeolites-microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1 nm, often goes hand-in-hand with diffusion limitations that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which reduces diffusion path lengths and thus improves molecular diffusion. This has been realized by synthesizing zeolite nanocrystals, by exfoliating layered zeolites, and by introducing mesopores in the microporous material through templating strategies or demetallation processes. But except for the exfoliation, none of these strategies has produced 'ultrathin' zeolites with thicknesses below 5 nm. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolite nanosheets that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The large number of acid sites on the external surface of these zeolites renders them highly active for the catalytic conversion of large organic molecules, and the reduced crystal thickness facilitates diffusion and thereby dramatically suppresses catalyst deactivation through coke deposition during methanol-to-gasoline conversion. We expect that our synthesis approach could be applied to other zeolites to improve their performance in a range of important catalytic applications.

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Topics: Microporous material (58%), ZSM-5 (57%), Zeolite (54%) ... read more

1,583 Citations

Open accessJournal ArticleDOI: 10.1021/ACS.CHEMREV.7B00776
Lichen Liu1, Avelino Corma1Institutions (1)
16 Apr 2018-Chemical Reviews
Abstract: Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

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Topics: Nanoclusters (70%), Organic reaction (54%), Catalysis (52%) ... read more

1,572 Citations

Open accessJournal ArticleDOI: 10.1021/CR500486U
19 Jun 2015-Chemical Reviews

662 Citations