Synthesis of efficient and reusable catalyst of size-controlled Au nanoparticles within a porous, chelating and intelligent hydrogel for aerobic alcohol oxidation

Wang, Yao; Yan, Rui; Zhang, Jianzheng; Zhang, Wangqing

doi:10.1016/j.molcata.2009.10.026

Cited by 46 publications

(8 citation statements)

References 76 publications

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“…This fact, together with encapsulation of hydrophobic reactants and their concentration in a smaller volume rich of catalytic sites, makes it possible to obtain higher reaction rates. The enhancement of the reaction rate during hydrogel deswelling has been proved for the Suzuki and the Heck reactions, but a similar behavior was obtained by Zhang and coworkers [36] during the preparation of a composite catalyst for aerobic alcohol oxidation made of Au NPs embedded into PNIPAm-co-PMACHE hydrogel. In both the cases, the reversible swelling/deswelling of the hydrogel can be exploited also to obtain an easy separation and reuse of the catalytic system.…”

Section: Switchable Catalysis Based On Variation Of Ph Ionic Strengtsupporting

confidence: 71%

Switchable Stimuli-Responsive Heterogeneous Catalysis

Vassalini

Alessandri

2018

Catalysts

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Heterogeneous catalytic systems based on the use of stimuli-responsive materials can be switched from an "on" active state to an "off" inactive state, which contributes to endowing the catalysts with unique functional properties, such as adaptability, recyclability and precise spatial and temporal control on different types of chemical reactions. All these properties constitute a step toward the development of nature-inspired catalytic systems. Even if this is a niche area in the field of catalysis, it is possible to find in literature intriguing examples of dynamic catalysts, whose systematic analysis and review are still lacking. The aim of this work is to examine the recent developments of stimuli-responsive heterogeneous catalytic systems from the viewpoint of different approaches that have been proposed to obtain a dynamic control of catalytic efficiency. Because of the variety of reactions and conditions, it is difficult to make a quantitative comparison between the efficiencies of the considered systems, but the analysis of the different strategies can inspire the preparation of new smart catalytic systems.Catalysts 2018, 8, 569 2 of 25 fields [6] and mechanical stress [7], have also been exploited. A large variability can also be observed in the type of system response: variations of chemical properties, solubility, shape, volume, color, aggregation state, electrical properties, magnetic properties, mechanical properties, etc. are all possible. Thanks to this high versatility, artificial smart materials have found application in various sectors [8], ranging from medicine to national security and structural engineering [9]. They are commonly employed for drug delivery [10], self-healing [11], sensing [12], actuations [13], information storage [14], etc. Their use for catalytic purposes has been remarkably less investigated, even if heterogeneous catalysis can fully take advantage of the dynamic behavior of smart materials. For example, it is possible to make a catalyst to pass from a state of activity (an "on" state) to a state of inertness (an "off" state) in a controlled way, with a precise temporal control, obtaining switchable catalysis. In other circumstances, the possibility of modulating the reaction rate in a continuous way, regulating the amount of accessible active sites and accelerating or lowering the reaction rate in a non-discrete way, is more interesting, and in this case we can also exploit stimuli-responsive materials. It is also possible to create microenvironments in which the reaction occurs preferentially, accomplishing a spatial control on the reaction development. In addition, the responsiveness of the employed systems can be exploited to improve the recyclability of the catalytic system, making the catalyst separation from the reaction medium and its reuse easier.In this review, we analyze some of the latest works on dynamic systems in the field of heterogeneous catalysis. Many more examples can be found for homogeneous catalysis, but most of them have been already analyzed in previ...

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Section: Switchable Catalysis Based On Variation Of Ph Ionic Strengtsupporting

confidence: 71%

Switchable Stimuli-Responsive Heterogeneous Catalysis

Vassalini

Alessandri

2018

Catalysts

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“…For nonoxide supports, catalytic activity increased as the size of Au NPs decreased when compared using the same supports: HT (2.1–12 nm), HAP (1.7–7.7 nm), MOF (2.2–9.8 nm), , carbon (3.4–8.9 nm), and polymers (2.6–6.3 nm). , Because of the lack of oxygen vacancies or active lattice oxygen for these supports, smaller Au NPs that facilitate O 2 activation might be a critical factor to determine the catalytic activity.…”

Section: Catalysis By Gold In Liquid-phase Reactionsmentioning

confidence: 99%

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

et al. 2019

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Since the discovery of catalysis by Au nanoparticles (NPs), unique catalytic features of Au have appeared that are greatly different from those of Pd and Pt. In this Review, we aimed to disclose how the unique catalytic abilities of Au are generated with respect to (a) the contact structures between Au and its supports and (b) the size of the Au particles. For CO oxidation, the catalytic activity of Au on reducible metal oxides (MO x ) is strongly correlated with the amount of oxygen vacancies of the MO x surface, which play a key role in O2 activation. Single atoms, bilayers of Au, sub-nm clusters, clusters (1–2 nm), and NPs (2–5 nm) have been proposed as the active sizes of the Au species, which may depend on the type of support. For propylene epoxidation, the presence of isolated TiO4 units in SiO2 supports is important for the production of propylene oxide (PO). Au NPs facilitate the formation of Ti–OOH species, which leads to PO in the presence of H2 and O2, whereas Au clusters facilitate propylene hydrogenation. However, Au clusters can produce PO by using only O2 and water, whereas Au NPs cannot. For alcohol oxidation, the reducibility of the MO x supports greatly influences the catalytic activity of Au, and single Au atoms more effectively activate the lattice oxygen of CeO2. The basic and acidic sites of the MO x surface also play an important role in the deprotonation of alcohols and the activation of aldehydes, respectively. For selective hydrogenation, heterolytic dissociation of H2 takes place at the interface between Au and MO x , and the basic sites of MO x contribute to H2 activation. Recent research into the reaction mechanisms and the development of well-designed Au catalysts has provided new insights into the preparation of high-performance Au catalysts.

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“…A thermoresponsive and pH-responsive, chelating, and superabsorbent hydrogel of poly(NIPAM)-co-poly[2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxypropyl ester] was synthesized and proposed as both a reaction medium and a recyclable Pd catalyst support for Suzuki, Heck, and other organic reactions [69]. Same polymer system with gold nanoparticles was demonstrated also to concentrate reactants within the hydrogel matrix through the reversible deswelling [70]. …”

Section: Overview Of Gel-based Materials By Applicationmentioning

confidence: 99%

Role of mechanical factors in applications of stimuli-responsive polymer gels – Status and prospects

Goponenko

Dzenis

2016

Polymer

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Due to their unique characteristics such as multifold change of volume in response to minute change in the environment, resemblance of soft biological tissues, ability to operate in wet environments, and chemical tailorability, stimuli responsive gels represent a versatile and very promising class of materials for sensors, muscle-type actuators, biomedical applications, and autonomous intelligent structures. Success of these materials in practical applications largely depends on their ability to fulfill application-specific mechanical requirements. This article provides an overview of recent application-driven development of covalent polymer gels with special emphasis on the relevant mechanical factors and properties. A short account of mechanisms of gel swelling and mechanical characteristics of importance to stimuli-responsive gels is presented. The review highlights major barriers for wider application of these materials and discusses latest advances and potential future directions toward overcoming these barriers, including interpenetrating networks, homogeneous networks, nanocomposites, and nanofilamentary gels.

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Synthesis of efficient and reusable catalyst of size-controlled Au nanoparticles within a porous, chelating and intelligent hydrogel for aerobic alcohol oxidation

Cited by 46 publications

References 76 publications

Switchable Stimuli-Responsive Heterogeneous Catalysis

Switchable Stimuli-Responsive Heterogeneous Catalysis

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

Role of mechanical factors in applications of stimuli-responsive polymer gels – Status and prospects

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