Showing papers by "Omar M. Yaghi published in 2005"

Porous, Crystalline, Covalent Organic Frameworks

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).

Strategies for hydrogen storage in metal--organic frameworks.

Abstract: Increased attention is being focused on metal-organic frameworks as candidates for hydrogen storage materials. This is a result of their many favorable attributes, such as high porosity, reproducible and facile syntheses, amenability to scale-up, and chemical modification for targeting desired properties. A discussion of several strategies aimed at improving hydrogen uptake in these materials is presented. These strategies include the optimization of pore size and adsorption energy by linker modification, impregnation, catenation, and the inclusion of open metal sites and lighter metals.

Rod packings and metal-organic frameworks constructed from rod-shaped secondary building units.

Abstract: The principal structure possibilities for packing infinite rod-shaped building blocks are described. Some basic nets derived from linking simple rods (helices and ladders) are then enumerated. We demonstrate the usefulness of the concept of rod secondary building units in the design and synthesis of metal-organic frameworks (MOFs). Accordingly, we present the preparation, characterization, and crystal structures of 14 new MOFs (named MOF-69A-C and MOF-70-80) of 12 different structure types, belonging to rod packing motifs, and show how their structures are related to basic nets. The MOFs reported herein are of polytopic carboxylates and contain one of Zn, Pb, Co, Cd, Mn, or Tb. The inclusion properties of the most open members are presented as evidence that MOF structures with rod building blocks can indeed be designed to have permanent porosity and rigid architectures.

Reticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of Frameworks

Abstract: The structures of all 1127 three-periodic extended metal−organic frameworks (MOFs) reported in the Cambridge Structure Database have been analyzed, and their underlying topology has been determined. It is remarkable that among the almost infinite number of net topologies that are available for MOFs to adopt, only a handful of nets are actually observed. The discovery of this inversion between expected and observed nets led us to deduce a system of classification “taxonomy” for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis has been approached. Specifically, three levels of complexity are defined that embody rules “grammar” for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that “codes” for a specif...

Gas Adsorption Sites in a Large-Pore Metal-Organic Framework

Abstract: The primary adsorption sites for Ar and N2 within metal-organic framework-5, a cubic structure composed of Zn4O(CO2)6 units and phenylene links defining large pores 12 and 15 angstroms in diameter, have been identified by single-crystal x-ray diffraction. Refinement of data collected between 293 and 30 kelvin revealed a total of eight symmetry-independent adsorption sites. Five of these are sites on the zinc oxide unit and the organic link; the remaining three sites form a second layer in the pores. The structural integrity and high symmetry of the framework are retained throughout, with negligible changes resulting from gas adsorption.

Design, Synthesis, Structure, and Gas (N2, Ar, CO2, CH4, and H2) Sorption Properties of Porous Metal-Organic Tetrahedral and Heterocuboidal Polyhedra

Abstract: A strategy based on assembling metal ions and organic carboxylate links has been applied for the design and synthesis of a new class of porous, truncated tetrahedral and heterocuboidal polyhedra, whose pore size and functionality can be systematically varied. The synthesis of this series of metal-organic polyhedra (MOPs) employs sulfate-capped oxygen-centered iron-carboxylate trimers, Fe3O(CO2)3(-)(SO4)3, as rigid nodes separated by linear (phenyl, biphenyl, terphenyl, and tetrahydropyrene) or trigonal (benzenetriphenyl) links to yield five highly crystalline polyhedra of general formula [NH2(CH3)2]8[Fe12O4(-)(SO4)12(link)x(py)12].G (x = 6 for linear or 4 for trigonal, py = pyridine, G = guests). In this series, the size of each polyhedron has been varied from 20.0 to 28.5 A (on edge), and the corresponding pore diameter from 7.3 to 13.3 A. Gas sorption isotherms were measured for three members of this series to reveal significant uptake of gases (N2, Ar, CO2, H2, CH4) and benzene and exhibit Type I sorption behavior that is indicative of permanent porosity. The apparent surface areas for these compounds range from 387 to 480 m(2)/g.

Characterization of H2 binding sites in prototypical metal-organic frameworks by inelastic neutron scattering.

Abstract: The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials.

Metal-Organic Frameworks Based on Trigonal Prismatic Building Blocks and the New “acs” Topology

Abstract: Cationic and mixed-valent forms of Fe3O(CO2)6 trigonal prismatic clusters have been linked by ditopic links, namely, 1,4-benzenedicarboxylate (1,4-BDC) and 1,3-benzenedicarboxylate (1,3-BDC), to produce two 3-periodic metal-organic frameworks (MOFs), [Fe3O(1,4-BDC)3 (DMF)3][FeCl4] x (DMF)3 (MOF-235) and Fe3O(1,3-BDC)3 (py)3 x (py)0.5(H2O)1.5 (MOF-236) (DMF = N,N-dimethylformamide, py = pyridine), respectively. These MOFs exemplify a new, high-symmetry topology termed acs which we identify here as the default arrangement for linking trigonal prisms together.

Porous metal-organic truncated octahedron constructed from paddle-wheel squares and terthiophene links.

Abstract: A metal−organic truncated octahedron (termed MOP-28) has been constructed from six rigid square-shaped Cu2(CO2)4 paddle-wheel building units and twelve 2,2‘:5‘,2‘ ‘-terthiophene-5,5‘ ‘-dicarboxylate (TTDC) linkers. TTDC linker in the cis,cis conformation provides the critical 90° linkage for this unique construction. The porous structure of MOP-28 is maintained even after the removal of guest species, as evidenced by this compound's nitrogen sorption isotherm of Type I characteristics and unprecedented surface area (Langmuir surface area 1100 m2/g, BET surface area 914 m2/g) among materials composed of discrete molecules.

Strategien für die Wasserstoffspeicherung in metall‐organischen Kompositgerüsten

Abstract: Metall-organische Geruste finden verstarkt Interesse als mogliche Materialien zur Wasserstoffspeicherung. Hintergrund dieser Forschungen sind die zahlreichen herausragenden Merkmale dieser Substanzen – wie hohe Porositat, reproduzierbare und einfache Synthesen, leichte Skalierbarkeit und die Moglichkeit zur gezielten chemischen Modifizierung zur Einstellung gewunschter Eigenschaften. Dieser Kurzaufsatz diskutiert Strategien zur Verbesserung der Wasserstoffaufnahme durch metall-organische Geruste. Die Ansatze umfassen die Optimierung der Porengrose und Adsorptionsenergien durch Modifizierung von Linkern, durch Impragnierung und Catenierung sowie durch den Einbau von koordinativ ungesattigten Metallzentren und Leichtmetallen.

Transformation of a metal-organic framework from the NbO to PtS net.

Abstract: Two metal−organic frameworks (MOFs), MOF-501 and MOF-502, respectively, formulated as Co2(BPTC)(H2O)5·Gx and Co2(BPTC)(H2O)(DMF)2·Gx (BPTC = 3,3‘,5,5‘-biphenyltetracarboxylate; G = guest molecules), have been synthesized and structurally characterized, and their topologies were found to be based on the NbO (MOF-501) and PtS (MOF-502) nets. Heating MOF-501 in solution results in the more thermodynamically favored MOF-502.

Covalently linked organic frameworks and polyhedra

Abstract: A covalently linked organic network includes a plurality of boron-containing clusters linked together by a plurality of linking groups. The covalently linked organic networks are characterized by having each linking group bonded to at least two distinct boron-containing clusters.

Organometallic framework material, preparation and use

Abstract: A process for preparing an organometallic framework material comprising reacting at least one metal salt with at least one at least bidentate compound capable of coordination to the metal ion of said metal salt, in the presence of an aqueous solvent system and at least one base wherein at least one bidentate compound comprises at least carboxy group and at least one further group which is not a carboxy group and which is capable of forming a hydrogen bridge linkage.

Hydrogen Storage in Metal-Organic Frameworks

Abstract: Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogenmore » storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up 15 wt% of total H2 uptake at 80 bar and 77 K. More importantly, the total H2 uptake by MOF-210 was 2.7 wt% at 80 bar and 298 K, which is the highest number reported for physisorptive materials.« less

Strategies for Hydrogen Storage in Metal—Organic Frameworks

Abstract: Increased attention is being focused on metal-organic frameworks as candidates for hydrogen storage materials. This is a result of their many favorable attributes, such as high porosity, reproducible and facile syntheses, amenability to scale-up, and chemical modification for targeting desired properties. A discussion of several strategies aimed at improving hydrogen uptake in these materials is presented. These strategies include the optimization of pore size and adsorption energy by linker modification, impregnation, catenation, and the inclusion of open metal sites and lighter metals.

Reticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of Frameworks

Abstract: The structures of all 1127 three-periodic extended metal−organic frameworks (MOFs) reported in the Cambridge Structure Database have been analyzed, and their underlying topology has been determined. It is remarkable that among the almost infinite number of net topologies that are available for MOFs to adopt, only a handful of nets are actually observed. The discovery of this inversion between expected and observed nets led us to deduce a system of classification “taxonomy” for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis has been approached. Specifically, three levels of complexity are defined that embody rules “grammar” for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that “codes” for a specif...

Canevas organiques lies par covalence et polyedres

Abstract: Reseau organique lie par covalence qui comprend une pluralite d'agregats contenant du bore lies par une pluralite de groupes de liaison. Les reseaux organiques lies par covalence sont caracterises en ce qu'ils presentent chacun un groupe de liaison lie avec au moins deux agregats differents contenant du bore.

Reticular Chemistry: Occurrence and Taxonomy of Nets and Grammar for the Design of

Abstract: The structures of all 1127 three-periodic extended metal-organic frameworks (MOFs) reported in the Cambridge Structure Database have been analyzed, and their underlying topology has been determined. It is remarkable that among the almost infinite number of net topologies that are available for MOFs to adopt, only a handful of nets are actually observed. The discovery of this inversion between expected and observed nets led us to deduce a system of classification “taxonomy” for interpreting and rationalizing known MOF structures, as well as those that will be made in future. The origin of this inversion is attributed to the different modes with which MOF synthesis has been approached. Specifically, three levels of complexity are defined that embody rules “grammar” for the design of MOFs and other extended structures. This system accounts for the present proliferation of MOF structures of high symmetry nets, but more importantly, it provides the basis for designing a building block that “codes” for a specific structure and, indeed, only that structure.