Polymerization of Alkynes in the Channels of Mesoporous Materials Containing Ni and Zn Cations:  Almost Complete Filling of the Voids

Cardin, D. J.; Constantine, S.; Gilbert, Andrew; Lay, Alexander K.; Álvaro, Mercedes; Galletero, Marı́a S.; Garcı́a, Hermenegildo; Márquez, Francisco

doi:10.1021/ja002921f

Cited by 53 publications

(43 citation statements)

References 19 publications

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“…We note that precedents in the literature working with highly reactive polyacetylene and other conducting polymers have shown that HF treatment allows dissolving the zeolite structure without producing changes in the highly reactive conducting organic polymer. 37,38 In general organic compounds are more stable to HF treatment than zeolite aluminosilicate framework, and in particularly all-silica ITQ-29 that is a relatively unstable material easy to be attacked by HF. 39 However, caution should be taken considering that HF digestion even at near ambient temperature can produce alteration on the original carbonised residue with respect to the morphology and photoluminescence properties of the entrapped C-dots.…”

Section: Introductionmentioning

confidence: 99%

Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

et al. 2015

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Abstract.C-dots obtained in homogeneous phase may exhibit a broad particle size distribution. Formation of C-dots within nanometric reaction cavities could be a methodology to gain control on their size distribution. Among the various possibilities, in the present work, the cavities of small pore size zeolites have been used to confine C-dots generated by pyrolysis of the organic structure directing agent present in the synthesis of these crystalline aluminosilicates. To explore this methodology, ITQ-29 zeolite having a Linde type A (LTA) structure was prepared as pure silica with 4-methyl-2,3,6,7-tetrahydro-1H,5H-pyrido[3.2.1-ij]quinolinium as organic structure directing agent. Pyrolysis under inert atmosphere at 550 ºC of a pure-silica ITQ-29 sample (cubic particles of 4 m edge) renders a highly fluorescent zeolite containing about 15 wt.% of carbonised residue. While other small pore zeolite, ITQ-12 (ITW), also renders photoluminescence C-dots under similar conditions, medium or large pore zeolites, such as silicalite (MFI) or pure silica Beta (BEA), failed to produce fluorescent powders under analogous thermal treatment and only decomposition and complete removal of the corresponding quaternary ammonium ion templates was observed for these zeolites. Dissolution of the pyrolysed ITQ-29 zeolite framework and extraction of the carbon residue with ethyl acetate has allowed characterisation of C-dots with particle size between 5-12 nm and a photoluminescence quantum yield of 0.4 upon excitation at 350 nm that is among the highest reported for non surface functionalized C-dots. The photoluminescence varies with the excitation wavelength and is quenched by oxygen. Pyrolysed ITQ-29 powders can act as fluorescent oxygen sensor.

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Section: Introductionmentioning

confidence: 99%

Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

et al. 2015

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“…35,37 (ii) Efficiency of the cross-coupling polymerization mechanisms (A þ BfAB, BþAB..fBAB.., etc.). A natural expectation is that this mechanism will not be efficient for singlefile systems because of the formation of many small oligomers within the pore which cannot react because of neighboring ends being of the same type.…”

Section: Discussionmentioning

confidence: 99%

“…35 Another study reported an almost complete (up to 75%) filling of MCM-41 pore volumes with polymerized alkanes. 37 Our modeling for the A þ A n fA nþ1 polymerization mechanism assumes a single-file (no passing) constraint for monomers and polymers inside the pore. The pore is represented by a linear lattice with lattice constant corresponding to the monomer length and pore length L = 200.…”

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Interplay between Anomalous Transport and Catalytic Reaction Kinetics in Single-File Nanoporous Systems

et al. 2011

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Functionalized nanoporous materials have broad utility for catalysis applications. However, the kinetics of catalytic reaction processes in these systems can be strongly impacted by the anomalous transport. The most extreme case corresponds to single-file diffusion for narrow pores in which species cannot pass each other. For conversion reactions with a single-file constraint, traditional mean-field-type reaction-diffusion equations fail to capture the initial evolution of concentration profiles, and they cannot describe the scaling behavior of steady-state reactivity. Hydrodynamic reaction-diffusion equations accounting for the single-file aspects of chemical diffusion can describe such initial evolution, but additional refinements are needed to incorporate fluctuation effects controlling, for example, steady-state reactivity localized near pore openings. For polymerization reactions with a single-file constraint, initial behavior depends strongly on system details such as catalytic site loading and reaction rate. However, long-time behavior often involves the formation of a dominant large polymer near each end of the pore, initially within the pore but subsequently partly extruding. In this partial extrusion regime, the kinetics is governed by the special features of the random walk describing the motion of the end of the partly extruded polymer, noting that this extruded end must return within the pore for further growth.

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“…The mechanism of polymerization of ethyne, propyne, and butyne in H-ZSM-5 has been studied by a range of spectroscopic techniques. [33,34] An important point in terms of the materials is the observation [33] that the products show a bimodal distribution of polymer [(CHCH) n ] molecular weight, with n = 3±6 and n = 14±¥, the latter range being favored for reactions occurring above 420 K. Much more recently it has been shown [35,36] that, in zeolites exchanged with Ni II or Co II cations, ethyne polymerizes rapidly at low temperatures to give complete filling of the voids. The materials were characterized by Raman spectroscopy, infrared sprectroscopy (IR), thermal gravimetry analysis (TGA), electronic spectra, X-ray photoelectron spectroscopy (XPS), and shown to form polyacetylene which fills the voids fully, so that the composites are stable to air indefinitely, presumably because oxygen cannot gain access to the polyene chain.…”

Section: Conducting Polymers In Zeolitesmentioning

confidence: 99%

“…[35] In any bulk application where the electrochemical properties of the composite are to be employed, mesopores have the considerable advantage over micropores that the active component is a much higher weight fraction. As an example, if such a composite were to be employed as a charge-storage element in a battery, comparability with current battery materials requires a minimum polymer content of 25 % by mass.…”

Section: Mesoporous Hosts and Related Materialsmentioning

confidence: 99%

Encapsulated Conducting Polymers

Cardin¹

2002

Adv. Mater.

201

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Conjugated polymers have an enormous range of potential applications, and recent work shows how many of these can be realized practically. Encapsulation can offer advantages in terms of separating polymer chains to inhibit interchain effects, improving the mechanical, thermal, and chemical stabilities of the assemblies, and possibly allowing individual molecular wires to be addressed. The Figure shows a schematic representation of a polyrotaxane, i.e., a polymer threaded into a host tube and held in place by end caps.

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Polymerization of Alkynes in the Channels of Mesoporous Materials Containing Ni and Zn Cations: Almost Complete Filling of the Voids

Cited by 53 publications

References 19 publications

Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

Interplay between Anomalous Transport and Catalytic Reaction Kinetics in Single-File Nanoporous Systems

Encapsulated Conducting Polymers

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