Porphyrin-Based Thin-Film Molecular Materials with Highly Adjustable Nanoscale Porosity and Permeability Characteristics

Bélanger, Suzanne; Hupp, Joseph T.

doi:10.1002/(sici)1521-3773(19990802)38:15<2222::aid-anie2222>3.0.co;2-4

Cited by 103 publications

(80 citation statements)

References 1 publication

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“…While 2 allowed permeation of iron phenanthroline, thin-film membranes of the functionalized square 3 blocked its permeation, allowing only trace amounts through even after 250 h of exposure. However, 3 remained highly permeable to phenol; similar findings have been reported based on electrochemical measurements [14,15]. This is a strong indication that transport through the porphyrin square films is governed by diffusion of penetrants through the interior square cavities rather than through voids between the squares.…”

Section: Introductionsupporting

confidence: 84%

Vapor permeation studies of membranes made from molecular squares

Czaplewski¹,

Li²,

Hupp³

et al. 2003

Journal of Membrane Science

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Thin-film membranes have been made from cavity-containing supramolecular building blocks known as molecular squares and evaluated for simple test separations. Permeation properties of single components and binary gas mixtures were measured through membranes made of several different molecular squares. For a small square with pyrazine edges, permeation increased in the order cyclohexane < benzene < toluene, consistent with the selectivities predicted from the sorption coefficients. Diffusion rates also play an important role in the permeation selectivity. For a larger square with porphyrin edges, mixture selectivities for 4-picoline over toluene were observed to be around 7-9, depending on the partial pressure. Functionalization of the interior of the porpyrin square allowed a mixture selectivity of 7 for benzene over cyclohexane. Independently measured adsorption isotherms and effective diffusion coefficients proved very helpful in understanding the effects of sorption and diffusion on the observed permeabilities.

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Section: Introductionsupporting

confidence: 84%

Vapor permeation studies of membranes made from molecular squares

Czaplewski¹,

Li²,

Hupp³

et al. 2003

Journal of Membrane Science

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“…Clearly, in the limit where L approaches zero, the approximation of the effective generator area by the tip area becomes exact. For the approach conditions used here, we have previously found that the approximation works well; the simplified SECM analysis returns transport parameters that agree closely with those obtained from exact analyses of RDE (17,21) and microelectrode measurements. Given the approximate equivalence under these conditions, we have replaced the difficult footprint͞ collection-efficiency problem with the simpler problem here of calculating the film flux as if the film were located at the tip electrode.…”

Section: ϫ1/2supporting

confidence: 70%

“…Consistent with channel formation, molecular-square film samples that retain some crystallinity typically transport probe molecules 20 to 50 times faster than amorphous metallopolymeric materials displaying similar molecular size cutoffs (18,19). Finally, with large squares, cavity functionalization has been demonstrated (20), and the functionalization chemistry has been exploited to tune molecular size cutoffs in a systematic fashion (13,17,21).…”

mentioning

confidence: 91%

Shape-selective transport through rectangle-based molecular materials: Thin-film scanning electrochemical microscopy studies

Williams

Benkstein

Abel

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Microporous thin films (Ϸ50 to 400 nm) composed of discrete, cavity-containing molecular rectangles have been prepared. The films, which contain both amorphous and microcrystalline domains, display shape-selective transport behavior. They are permeable to small molecules and to molecules that are short or narrow in at least one dimension-for example, elongated planar molecules-but are impermeable to molecules lacking a narrow dimension. However, the shape selectivity is based on transport through intramolecular rather than intermolecular cavities. By using redox-active probe molecules, rates of transport through the rectangle-based material have been extracted from electrochemical measurements. Spatially resolved measurements obtained via scanning electrochemical microscopy have permitted transport through individual microcrystals to be evaluated semiquantitatively. The measurements reveal that transport is roughly two orders of magnitude slower than observed with thin microcrystalline films of molecular squares featuring similar-sized cavities. The differences likely reflect the fact that cavities within the squarebased materials, but not the rectangle-based material, align to form simple one-dimensional channels.

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“…56,58 In their studies, advantage was taken of zinc ions configured in the center of each porphyrin wall to axially ligate difunctional or tetrafunctional porphyrins and predictably reduce the cavity dimensions (Figure 7). Benkstein and Williams extended the investigations to thin films composed of the molecular rectangle, 10.…”

Section: Applications: Molecular Sievingmentioning

confidence: 99%

Supramolecular Coordination Chemistry and Functional Microporous Molecular Materials

Dinolfo¹,

2001

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An enormous number and variety of discrete, isolable, supramolecular-coordinationchemistry-based assemblies featuring well-defined nanoscale cavities have been designed, synthesized, and characterized over the past decade. A small number of these have subsequently been used as building blocks for microporous materials and now comprise an important component of an emerging chemistry of microporous molecular materials. The extant materials typically have displayed large void volumes, high internal surface areas, and the ability to withstand the systematic removal of solvent. These and other properties (chemical tailorability, alignment of cavities to form extended channels, good processability, etc.) suggest a number of potentially very exciting applications involving selective molecular transport, sensing, or chemical transformationswith many of these now supported by proofof-concept experiments.

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Porphyrin-Based Thin-Film Molecular Materials with Highly Adjustable Nanoscale Porosity and Permeability Characteristics

Cited by 103 publications

References 1 publication

Vapor permeation studies of membranes made from molecular squares

Vapor permeation studies of membranes made from molecular squares

Shape-selective transport through rectangle-based molecular materials: Thin-film scanning electrochemical microscopy studies

Supramolecular Coordination Chemistry and Functional Microporous Molecular Materials

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