Unintuitive Inverse Dependence of the Apparent Turnover Frequency on Precatalyst Concentration: A Quantitative Explanation in the Case of Ziegler-Type Nanoparticle Catalysts Made from [(1,5-COD)Ir(μ-O2C8H15)]2 and AlEt3

Crooks, Adam B.; Yih, Kuang-Hway; Li, Long; Yang, Judith C.; Özkâr, Saim; Finke, Richard G.

doi:10.1021/acscatal.5b00347

Cited by 30 publications

(22 citation statements)

References 40 publications

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“…Some researchers tend to use the number of surface atoms or amount of cocatalysts to calculate the TOF, namely the apparent TOF. Considering the fact that the number of active sites may not be proportional to the surface atoms, the apparent TOF should be much lower than the real TOF . For example, only edge atoms are active for redox reactions on some catalysts .…”

Section: Fundamentals In Photocatalysismentioning

confidence: 99%

Hollow Nanostructures for Photocatalysis: Advantages and Challenges

et al. 2018

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Photocatalysis for solar-driven reactions promises a bright future in addressing energy and environmental challenges. The performance of photocatalysis is highly dependent on the design of photocatalysts, which can be rationally tailored to achieve efficient light harvesting, promoted charge separation and transport, and accelerated surface reactions. Due to its unique feature, semiconductors with hollow structure offer many advantages in photocatalyst design including improved light scattering and harvesting, reduced distance for charge migration and directed charge separation, and abundant surface reactive sites of the shells. Herein, the relationship between hollow nanostructures and their photocatalytic performance are discussed. The advantages of hollow nanostructures are summarized as: 1) enhancement in the light harvesting through light scattering and slow photon effects; 2) suppression of charge recombination by reducing charge transfer distance and directing separation of charge carriers; and 3) acceleration of the surface reactions by increasing accessible surface areas for separating the redox reactions spatially. Toward the end of the review, some insights into the key challenges and perspectives of hollow structured photocatalysts are also discussed, with a good hope to shed light on further promoting the rapid progress of this dynamic research field.

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Section: Fundamentals In Photocatalysismentioning

confidence: 99%

Hollow Nanostructures for Photocatalysis: Advantages and Challenges

et al. 2018

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“…Recently, Finke and co-workers have analyzed similar counterintuitive behavior in hydrogenations with Ziegler-type nanoparticle catalysts prepared from Ir precatalysts (30). Likewise, benzene borylation has been described with Ir nanoparticles at 80°C with activities that are considerably lower than those for homogeneous catalysts (31).…”

mentioning

confidence: 99%

Catalytic borylation of methane

Smith

Berritt

González-Moreiras

et al. 2016

Science

169

122

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Despite steady progress in catalytic methods for the borylation of hydrocarbons, methane has not yet been subject to this transformation. Here we report the iridium-catalyzed borylation of methane using bis(pinacolborane) in cyclohexane solvent. Initially, trace amounts of borylated products were detected with phenanthroline-coordinated Ir complexes. A combination of experimental high-pressure and high-throughput screening, and computational mechanism discovery techniques helped to rationalize the foundation of the catalysis and identify improved phosphine-coordinated catalytic complexes. Optimized conditions of 150°C and 3500-kilopascal pressure led to yields as high as ∼52%, turnover numbers of 100, and improved chemoselectivity for monoborylated versus diborylated methane.

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“…Previous reports detailingachanging TOF relatedt he effect to association/dissociationo fc atalyst, supportedb yk inetic data. [47] We hypothesize that catalyst order is continually decreasing with increasing concentration of 1a;V TNA was conducted above andb elow 100 mm to highlight the difference in order. Am onomeric POSS-triol is proposed to be the active catalyst, suggesting the variable order in 1a is related to an off-cycle event that is more significant at higher concentrations.…”

Section: Resultsmentioning

confidence: 97%

“…Apparent turnover frequencies (TOF app = k obs /[ 1 a ]) vs. [ 1 a ]) were calculated, and it was observed that TOF app plateaus at catalyst concentrations >100 m m (see the Supporting Information). Previous reports detailing a changing TOF related the effect to association/dissociation of catalyst, supported by kinetic data …”

Section: Resultsmentioning

confidence: 99%

Kinetic and Binding Studies Reveal Cooperativity and Off‐Cycle Competition for H‐Bonding Catalysis with Silsesquioxane Silanols

Jagannathan

Diemoz

Targos

et al. 2019

Chemistry A European J

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The catalytic activity, kinetics, and quantification of H‐bonding ability of incompletely condensed polyhedral oligomeric silsesquioxane (POSS) silanols are reported. POSS‐triols, a homogeneous model for vicinal silica surface sites, exhibit enhanced H‐bonding compared with other silanols and alcohols as quantified using a 31P NMR probe. Evaluation of a Friedel–Crafts addition reaction shows that phenyl‐POSS‐triol is active as an H‐bond donor catalyst whereas other POSS silanols studied are not. An in‐depth kinetic study (using RPKA and VTNA) highlights the concentration‐dependent H‐bonding behavior of POSS‐triols, which is attributed to intermolecular association forming an off‐cycle dimeric species. Binding constants provide additional support for reduced H‐bond ability at higher concentrations, which is attributed to competitive association. POSS‐triol self‐association disrupts H‐bond donor abilities relevant for catalysis by reducing the concentration of active monomeric catalyst.

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Unintuitive Inverse Dependence of the Apparent Turnover Frequency on Precatalyst Concentration: A Quantitative Explanation in the Case of Ziegler-Type Nanoparticle Catalysts Made from [(1,5-COD)Ir(μ-O₂C₈H₁₅)]₂ and AlEt₃

Abstract: A 1 H NMR spectrum of the precursor was obtained via an Inova 400 MHz NMR instrument.

Cited by 30 publications

References 40 publications

Hollow Nanostructures for Photocatalysis: Advantages and Challenges

Hollow Nanostructures for Photocatalysis: Advantages and Challenges

Catalytic borylation of methane

Kinetic and Binding Studies Reveal Cooperativity and Off‐Cycle Competition for H‐Bonding Catalysis with Silsesquioxane Silanols

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