Porous, Crystalline, Covalent Organic Frameworks
18 Nov 2005-Science (American Association for the Advancement of Science)-Vol. 310, Iss: 5751, pp 1166-1170
TL;DR: Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid and hexahydroxytriphenylene to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms.
Abstract: Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C6H4[B(OH)2]2} and hexahydroxytriphenylene [C18H6(OH)6]. Powder x-ray diffraction studies of the highly crystalline products (C3H2BO)6.(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6(3)/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 degrees to 600 degrees C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).
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TL;DR: A new crystalline porous three-dimensional covalent organic framework, termed COF-300, has been synthesized and structurally characterized and shows thermal stability up to 490 degrees C and permanent porosity with a surface area of 1360 m(2) g(-1).
Abstract: A new crystalline porous three-dimensional covalent organic framework, termed COF-300, has been synthesized and structurally characterized. Tetrahedral tetra-(4-anilyl)-methane and linear terephthaldehyde building blocks were condensed to form imine linkages in a material whose X-ray crystal structure shows five independent diamond frameworks. Despite the interpenetration, the structure has pores of 7.2 A diameter. Thus, COF-300 shows thermal stability up to 490 degrees C and permanent porosity with a surface area of 1360 m(2) g(-1).
1,164 citations
TL;DR: How each application will limit the materials that can be used, and also the size and connectivity of the pores required, are reviewed to compare and contrast a growing range of porous materials that are finding increasing use in academic and industrial applications.
Abstract: From kitchen sieves and strainers to coffee filters, porous materials have a wide range of uses. On an industrial scale, they are used as sorbents, filters, membranes, and catalysts. Slater and Cooper review how each application will limit the materials that can be used, and also the size and connectivity of the pores required. They go on to compare and contrast a growing range of porous materials that are finding increasing use in academic and industrial applications.
Science , this issue [10.1126/science.aaa8075][1]
[1]: /lookup/doi/10.1126/science.aaa8075
1,152 citations
Cites background from "Porous, Crystalline, Covalent Organ..."
...P orous materials such as zeolites (1), metalorganic frameworks (MOFs) (2–4), covalent organic frameworks (COFs) (5), and porous polymers (6) have widespread uses in adsorption, catalysis, separation, purification, and energy storage and production....
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...2012 Alkane/alkene separation by a MOF (55) Covalent organic frameworks (COFs) (5) High pore volume MOF, MIL-101 (40)...
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TL;DR: Since the organic constituents of COFs, when linked, do not undergo significant change in their overall geometry, it has been possible to predict the structures of the resulting COF, and this advantage has facilitated their characterization using powder X-ray diffraction techniques, which has allowed for the synthesis of COF structures by design and for their formation with the desired composition, pore size, and aperture.
Abstract: Linking organic molecules by covalent bonds into extended solids typically generates amorphous, disordered materials. The ability to develop strategies for obtaining crystals of such solids is of interest because it opens the way for precise control of the geometry and functionality of the extended structure, and the stereochemical orientation of its constituents. Covalent organic frameworks (COFs) are a new class of porous covalent organic structures whose backbone is composed entirely of light elements (B, C, N, O, Si) that represent a successful demonstration of how crystalline materials of covalent solids can be achieved. COFs are made by combination of organic building units covalently linked into extended structures to make crystalline materials. The attainment of crystals is done by several techniques in which a balance is struck between the thermodynamic reversibility of the linking reactions and their kinetics. This success has led to the expansion of COF materials to include organic units linked by these strong covalent bonds: B-O, C-N, B-N, and B-O-Si. Since the organic constituents of COFs, when linked, do not undergo significant change in their overall geometry, it has been possible to predict the structures of the resulting COFs, and this advantage has facilitated their characterization using powder X-ray diffraction (PXRD) techniques. It has also allowed for the synthesis of COF structures by design and for their formation with the desired composition, pore size, and aperture. In practice, the modeled PXRD pattern for a given expected COF is compared with the experimental one, and depending on the quality of the match, this is used as a starting point for solving and then refining the crystal structure of the target COF. These characteristics make COFs an attractive class of new porous materials. Accordingly, they have been used as gas storage materials for energy applications, solid supports for catalysis, and optoelectronic devices. A large and growing library of linkers amenable to the synthesis of COFs is now available, and new COFs and topologies made by reticular synthesis are being reported. Much research is also directed toward the development of new methods of linking organic building units to generate other crystalline COFs. These efforts promise not only new COF chemistry and materials, but also the chance to extend the precision of molecular covalent chemistry to extended solids.
1,145 citations
TL;DR: This Atlas demonstrates the large diversity of electronic properties, including band gaps and electron mobilities of atomically thin materials, as well as rare earth, semimetals, transition metal chalcogenides and halides, and finally synthetic organic 2D materials, exemplified by 2D covalent organic frameworks.
Abstract: The discovery of graphene and other two-dimensional (2D) materials together with recent advances in exfoliation techniques have set the foundations for the manufacturing of single layered sheets from any layered 3D material. The family of 2D materials encompasses a wide selection of compositions including almost all the elements of the periodic table. This derives into a rich variety of electronic properties including metals, semimetals, insulators and semiconductors with direct and indirect band gaps ranging from ultraviolet to infrared throughout the visible range. Thus, they have the potential to play a fundamental role in the future of nanoelectronics, optoelectronics and the assembly of novel ultrathin and flexible devices. We categorize the 2D materials according to their structure, composition and electronic properties. In this review we distinguish atomically thin materials (graphene, silicene, germanene, and their saturated forms; hexagonal boron nitride; silicon carbide), rare earth, semimetals, transition metal chalcogenides and halides, and finally synthetic organic 2D materials, exemplified by 2D covalent organic frameworks. Our exhaustive data collection presented in this Atlas demonstrates the large diversity of electronic properties, including band gaps and electron mobilities. The key points of modern computational approaches applied to 2D materials are presented with special emphasis to cover their range of application, peculiarities and pitfalls.
1,136 citations
TL;DR: The unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and reactors, optical properties and applications, magnetic properties, energy storage, catalysis, biomedical applications, environmental remediation, and sensors are discussed.
Abstract: In this Review, we aim to provide an updated summary of the research related to hollow micro- and nanostructures, covering both their synthesis and their applications. After a brief introduction to the definition and classification of the hollow micro-/nanostructures, we discuss various synthetic strategies that can be grouped into three major categories, including hard templating, soft templating, and self-templating synthesis. For both hard and soft templating strategies, we focus on how different types of templates are generated and then used for creating hollow structures. At the end of each section, the structural and morphological control over the product is discussed. For the self-templating strategy, we survey a number of unconventional synthetic methods, such as surface-protected etching, Ostwald ripening, the Kirkendall effect, and galvanic replacement. We then discuss the unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and rea...
1,135 citations
References
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Book•
05 Oct 1998
TL;DR: In this paper, the authors provide an introductory review of the various theoretical and practical aspects of adsorption by powders and porous solids with particular reference to materials of technological importance.
Abstract: The declared objective of this book is to provide an introductory review of the various theoretical and practical aspects of adsorption by powders and porous solids with particular reference to materials of technological importance. The primary aim is to meet the needs of students and non-specialists, who are new to surface science or who wish to use the advanced techniques now available for the determination of surface area, pore size and surface characterization. In addition, a critical account is given of recent work on the adsorptive properties of activated carbons, oxides, clays and zeolites. Key Features * Provides a comprehensive treatment of adsorption at both the gas/solid interface and the liquid/solid interface * Includes chapters dealing with experimental methodology and the interpretation of adsorption data obtained with porous oxides, carbons and zeolites * Techniques capture the importance of heterogeneous catalysis, chemical engineering and the production of pigments, cements, agrochemicals, and pharmaceuticals
3,128 citations
"Porous, Crystalline, Covalent Organ..." refers background in this paper
...At higher pressures, a slow rise in the isotherm occurs because of the existence of a small population of external mesopores between the crystallites; this feature is not uncommon for particles with platelet morphologies (19)....
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...These values surpass those of other layered materials, including graphite (10 m(2) g), clays (10 to 100 m(2) g), and pillared clays (50 to 300 m(2) g) and are in the range of the most porous zeolites and many porous carbons (19)....
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...The total surface area was calculated to be 711 m(2) g, with a micropore contribution of 587 m(2) g (83%) and mesopore contribution of 124 m(2) g (17%) from de Boer statistical thickness (t-plot) analysis (19)....
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TL;DR: The surfactant-mediated synthesis of an ordered benzene–silica hybrid material has an hexagonal array of mesopores and crystal-like pore walls that exhibit structural periodicity, and it is expected that other organosilicas and organo-metal oxides can be produced in a similar fashion, to yield a range of hierarchically ordered mesoporous solids with molecular-scale pore surface periodicity.
Abstract: Surfactant-mediated synthesis strategies are widely used to fabricate ordered mesoporous solids in the form of metal oxides, metals, carbon and hybrid organosilicas. These materials have amorphous pore walls, which could limit their practical utility. In the case of mesoporous metal oxides, efforts to crystallize the framework structure by thermal and hydrothermal treatments have resulted in crystallization of only a fraction of the pore walls. Here we report the surfactant-mediated synthesis of an ordered benzene-silica hybrid material; this material has an hexagonal array of mesopores with a lattice constant of 52.5 A, and crystal-like pore walls that exhibit structural periodicity with a spacing of 7.6 A along the channel direction. The periodic pore surface structure results from alternating hydrophilic and hydrophobic layers, composed of silica and benzene, respectively. We believe that this material is formed as a result of structure-directing interactions between the benzene-silica precursor molecules, and between the precursor molecules and the surfactants. We expect that other organosilicas and organo-metal oxides can be produced in a similar fashion, to yield a range of hierarchically ordered mesoporous solids with molecular-scale pore surface periodicity.
1,216 citations
TL;DR: In this paper, a unified approach to pore size characterization of microporous carbonaceous materials such as activated carbon and carbon fibers by nitrogen, argon, and carbon dioxide adsorption at standard temperatures, 77 K for N2 and Ar and 273 K for CO2, was presented.
Abstract: We present a unified approach to pore size characterization of microporous carbonaceous materials such as activated carbon and carbon fibers by nitrogen, argon, and carbon dioxide adsorption at standard temperatures, 77 K for N2 and Ar and 273 K for CO2. Reference isotherms of N2, Ar, and CO2 in a series of model slit-shaped carbon pores in the range from 0.3 to 36 nm have been calculated from the nonlocal density functional theory (NLDFT) using validated parameters of intermolecular interactions. Carbon dioxide isotherms have also been generated by the grand canonical Monte Carlo (GCMC) method based on the 3-center model of Harris and Yung. The validation of model parameters includes three steps: (1) prediction of vapor−liquid equilibrium data in the bulk system, (2) prediction of adsorption isotherm on graphite surface, (3) comparison of the NLDFT adsorption isotherms in pores to those of GCMC simulations, performed with the parameters of fluid-fluid interactions, which accurately reproduce vapor−liqui...
657 citations
TL;DR: In this paper, the pore size of MCM-41 materials was estimated based on geometrical considerations of the ratio of pore volume to pore wall volume for an infinite hexagonal array of cylindrical pores.
Abstract: Nitrogen adsorption measurements were performed over a wide range of relative pressures (10-6−0.995) for a series of siliceous MCM-41 samples obtained using alkyltrimethylammonium surfactants with different chain length. Both high- and low-pressure adsorption data were analyzed. The pore size was shown to increase in a regular way with the chain length of the surfactant used. Moreover, a very good correlation between the pore size and the interplanar spacing of the MCM-41 samples was observed. Methods used to calculate the pore diameter were critically compared, and a new procedure to estimate the pore size of MCM-41 materials was proposed. This new procedure is based on geometrical considerations of the ratio of the pore volume to the pore wall volume for an infinite hexagonal array of cylindrical pores. Adsorption measurements showed that the amount adsorbed in the low-pressure region increases with a decrease in the pore size of the samples probably because of the enhancement of the gas−surface interac...
465 citations