Incarceration of (PdO)n and Pdn Clusters by Cage‐Templated Synthesis of Hollow Silica Nanoparticles

Takao, Kiyotaka; Suzuki, Kosuke; Ichijo, Tatsuya; Sato, Sota; Asakura, Hiroyuki; Teramura, Kentaro; Kato, Kazúo; Ohba, Tomonori; Morita, Takeshi; Fujita, Makoto

doi:10.1002/anie.201201288

Cited by 45 publications

(20 citation statements)

References 31 publications

(2 reference statements)

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“…In both the reported r ‐space EXAFS spectra of PdO nanoparticles and our studies of reference PdO sample, a peak at 3.1 Å was clearly identified, comparable in intensity to be the first nearest neighbor Pd−O contribution; this peak at 3.1 Å represents the contribution to EXAFS from the two closest Pd atoms in a PdO nanoparticle, bridged by an oxygen atom (Pd−O−Pd). Compared to other PdO nanoparticles and the reference PdO sample (red line in Figure ), however, the r ‐space spectrum of 0.04 wt % Pd/ZSM‐5 (blue line in Figure ) does not have such a distinct peak with the similar intensity as the Pd−Pd peak in PdO at ∼3.1 Å. Therefore, there is no evidence that any species or structure in 0.04 wt % Pd/ZSM‐5 contains Pd−O−Pd species, which indicates the absence of PdO nanoclusters.…”

Section: Figuresupporting

confidence: 54%

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate

et al. 2016

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Direct conversion of methane to chemical feedstocks such as methanol under mild conditions is a challenging but ideal solution for utilization of methane. Pd1O4 single‐sites anchored on the internal surface of micropores of a microporous silicate exhibit high selectivity and activity in transforming CH4 to CH3OH at 50–95 °C in aqueous phase through partial oxidation of CH4 with H2O2. The selectivity for methanol production remains at 86.4 %, while the activity for methanol production at 95 °C is about 2.78 molecules per Pd1O4 site per second when 2.0 wt % CuO is used as a co‐catalyst with the Pd1O4@ZSM‐5. Thermodynamic calculations suggest that the reaction toward methanol production is highly favorable compared to formation of a byproduct, methyl peroxide.

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Section: Figuresupporting

confidence: 54%

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate

et al. 2016

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“…Therefore, it was determined that Pt was present in cation‐exchange sites. After oxidation, the CN for the R‐space EXAFS peak at around 2.0 Å (corresponding to the PtO shell) increased from 2 to 2.8, suggesting that Pt oxo species was formed [ 61 ] with a 1:1 Pt:O ratio that facilitates the CO oxidation reaction. This transformation progress was further supported by scanning transmission electron microscopy (STEM) results ( Figure A–G).…”

Section: Xas Analysis Of Sacs Supported By Crystalline Porous Materialsmentioning

confidence: 99%

Single‐Atom Catalysts Supported by Crystalline Porous Materials: Views from the Inside

et al. 2020

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Reducing the size of nanoparticle catalysts is one desirable method that can improve their catalytic activity. Single-atom catalysts (SACs) represent the smallest possible size a catalyst can achieve with maximum atomic efficiency. [6] Moreover, recent studies have shown that the use of single-atom catalytic sites, rather than ensembles of atoms, is crucial in many catalytic reactions. [7] Without proper protection, however, single-atom sites in these catalysts are not stable since they tend to aggregate and form larger particles. [8-10] To solve this problem, many different protecting supports have been developed such as polymers and porous organic cages. [11,12] Crystalline porous materials, such as zeolites and metal-organic frameworks (MOFs), have been widely used to stabilize small metal species in catalytic reactions due to the controllable size, shape, and dimensions of their pores and channels. [13-15] Therefore, they are highly desirable in supporting SACs. [13] Despite the promising aspects of zeolite and MOF-supported SACs, their characterization remains challenging due to the single-atomic nature of their bonding environments; atomic-level resolution is needed for the structural characterization of these catalysts. X-ray absorption spectroscopy (XAS) is a powerful tool in studying the structure and properties of atoms in their coordination environments with subatomic resolution, [16,17] and thus is considered particularly suitable for the study of SACs. [16,17] In this contribution, a comprehensive review of representative works on zeolite-and MOF-protected SACs will be presented from the XAS perspective. The subatomic resolution (0.01 Å level) of synchrotron-based XAS technique allows for views from "inside" the SACs regarding their structure, electronic properties, and catalytic activities. The processed data from extended X-ray absorption fine structure (EXAFS) will be shown as a powerful tool to probe the atomic structure of SACs in zeolites and MOFs. Through the standard fitting analysis of EXAFS, together with the assistance of advanced analysis tools, detailed information concerning the local structure of SACs can be obtained. Additionally, it will be demonstrated that the X-ray absorption near-edge structure (XANES) can provide insight into the unique electronic properties of SACs. Furthermore, in situ/operando XAS techniques, coupled with state-of-the-art Single-atom catalysts (SACs) have recently emerged as an exciting system in heterogeneous catalysis showing outstanding performance in many catalytic reactions. Single-atom catalytic sites alone are not stable and thus require stabilization from substrates. Crystalline porous materials such as zeolites and metal-organic frameworks (MOFs) are excellent substrates for SACs, offering high stability with the potential to further enhance their performance due to synergistic effects. This review features recent work on the structure, electronic, and catalytic properties of zeolite and MOF-protected SACs, offering atomic-scale views from the "insid...

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“…11(b) This study revealed (Fig. 8) that replacing the bulky tetramethylethylenediamine (tmen) blocker with far less sterically demanding ethylenediamine (en), 55 results in the exclusive formation of triply interlocked trigonal prisms [(P17) 2 ]. However, on introducing guest molecules like trimesic acid (G3), the product that exclusively formed was the single prism with two guest molecules stacked inside the molecular architecture through π-π interactions.…”

Section: Neutral and Anionic Donorsmentioning

confidence: 99%

Template-free multicomponent coordination-driven self-assembly of Pd(ii)/Pt(ii) molecular cages

Mukherjee

2014

Chem. Commun.

199

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Recent years have seen a tremendous increase in the interest for constructing hollowed-out molecular frameworks, for their potential uses. Metal-ligand coordination-driven self-assembly has provided multitudes of opportunities in the formation of molecular architectures of desired shapes and sizes, with the help of the information already coded in the components. This article summarizes the recent developments in the construction of multicomponent molecular cages through this process, with a focus on the decreasing relevance of templates, and use of these systems in catalysis/host-guest chemistry.

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Incarceration of (PdO)_n and Pd_n Clusters by Cage‐Templated Synthesis of Hollow Silica Nanoparticles

Cited by 45 publications

References 31 publications

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate

Single‐Atom Catalysts Supported by Crystalline Porous Materials: Views from the Inside

Template-free multicomponent coordination-driven self-assembly of Pd(ii)/Pt(ii) molecular cages

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Incarceration of (PdO)n and Pdn Clusters by Cage‐Templated Synthesis of Hollow Silica Nanoparticles

Cited by 45 publications

References 31 publications

Low‐Temperature Transformation of Methane to Methanol on Pd1O4 Single Sites Anchored on the Internal Surface of Microporous Silicate

Low‐Temperature Transformation of Methane to Methanol on Pd1O4 Single Sites Anchored on the Internal Surface of Microporous Silicate

Single‐Atom Catalysts Supported by Crystalline Porous Materials: Views from the Inside

Template-free multicomponent coordination-driven self-assembly of Pd(ii)/Pt(ii) molecular cages

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Incarceration of (PdO)_n and Pd_n Clusters by Cage‐Templated Synthesis of Hollow Silica Nanoparticles

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate

Low‐Temperature Transformation of Methane to Methanol on Pd₁O₄ Single Sites Anchored on the Internal Surface of Microporous Silicate