Showing papers by "Omar M. Yaghi published in 2008"

High-throughput synthesis of zeolitic imidazolate frameworks and application to CO2 capture.

Abstract: A high-throughput protocol was developed for the synthesis of zeolitic imidazolate frameworks (ZIFs). Twenty-five different ZIF crystals were synthesized from only 9600 microreactions of either zinc(II)/cobalt(II) and imidazolate/imidazolate-type linkers. All of the ZIF structures have tetrahedral frameworks: 10 of which have two different links (heterolinks), 16 of which are previously unobserved compositions and structures, and 5 of which have topologies as yet unobserved in zeolites. Members of a selection of these ZIFs (termed ZIF-68, ZIF-69, and ZIF-70) have high thermal stability (up to 390°C) and chemical stability in refluxing organic and aqueous media. Their frameworks have high porosity (with surface areas up to 1970 square meters per gram), and they exhibit unusual selectivity for CO 2 capture from CO 2 /CO mixtures and extraordinary capacity for storing CO 2 : 1 liter of ZIF-69 can hold ∼83 liters of CO 2 at 273 kelvin under ambient pressure.

The Reticular Chemistry Structure Resource (RCSR) Database of, and Symbols for, Crystal Nets

Abstract: During the past decade, interest has grown tremendously in the design and synthesis of crystalline materials constructed from molecular clusters linked by extended groups of atoms. Most notable are metal-organic frameworks (MOFs), in which polyatomic inorganic metal-containing clusters are joined by polytopic linkers. (Although these materials are sometimes referred to as coordination polymers, we prefer to differentiate them, because MOFs are based on strong linkages that yield robust frameworks.) The realization that MOFs could be designed and synthesized in a rational way from molecular building blocks led to the emergence of a discipline that we call reticular chemistry. MOFs can be represented as a special kind of graph called a periodic net. Such descriptions date back to the earliest crystallographic studies but have become much more common recently because thousands of new structures and hundreds of underlying nets have been reported. In the simplest cases (e.g., the structure of diamond), the atoms in the crystal become the vertices of the net, and bonds are the links (edges) that connect them. In the case of MOFs, polyatomic groups act as the vertices and edges of the net. Because of the explosive growth in this area, a need has arisen for a universal system of nomenclature, classification, identification, and retrieval of these topological structures. We have developed a system of symbols for the identification of three periodic nets of interest, and this system is now in wide use. In this Account, we explain the underlying methodology of assigning symbols and describe the Reticular Chemistry Structure Resource (RCSR), in which about 1600 such nets are collected and illustrated in a database that can be searched by symbol, name, keywords, and attributes. The resource also contains searchable data for polyhedra and layers. The database entries come from systematic enumerations or from known chemical compounds or both. In the latter case, references to occurrences are provided. We describe some crystallographic, topological, and other attributes of nets and explain how they are reported in the database. We also describe how the database can be used as a tool for the design and structural analysis of new materials. Associated with each net is a natural tiling, which is a natural partition of space into space-filling tiles. The database allows export of data that can be used to analyze and illustrate such tilings.

Colossal cages in zeolitic imidazolate frameworks as selective carbon dioxide reservoirs

Abstract: Zeolitic imidazolate frameworks, or ZIFs, are porous crystalline materials in which organic imidazolate links connect to transition metals to form a tetrahedral framework. Many different ZIF structures can be created by simply adjusting the link–link interactions. Wang et al. used this tactic to produce two new materials with structures of a scale and complexity rarely seen before. The resulting cages contain up to 264 vertices within the pore network, and are constructed from as many as 7,524 atoms. The cages can selectively capture and store carbon dioxide with high efficiency and this, combined with stability and ease of fabrication, makes giant ZIFs promising candidates for technologies aimed at reducing carbon dioxide emissions. Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials where organic imidazolate links connect to transition metals to form a tetrahedral framework. Intriguingly, many different ZIF structures can be created by simply adjusting the link-link interactions. Links that result in two new materials with structures of a scale and complexity rarely seen before have now been designed: huge and complex cages within the pore network contain up to 264 vertices, and are constructed from as many as 7,524 atoms. Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials with tetrahedral networks that resemble those of zeolites: transition metals (Zn, Co) replace tetrahedrally coordinated atoms (for example, Si), and imidazolate links replace oxygen bridges1. A striking feature of these materials is that the structure adopted by a given ZIF is determined by link–link interactions, rather than by the structure directing agents used in zeolite synthesis2. As a result, systematic variations of linker substituents have yielded many different ZIFs that exhibit known or predicted zeolite topologies. The materials are chemically and thermally stable, yet have the long-sought-after design flexibility offered by functionalized organic links and a high density of transition metal ions1,2,3,4,5,6,7. Here we report the synthesis and characterization of two porous ZIFs—ZIF-95 and ZIF-100—with structures of a scale and complexity previously unknown in zeolites8,9,10. The materials have complex cages that contain up to 264 vertices, and are constructed from as many as 7,524 atoms. As expected from the adsorption selectivity recently documented for other members of this materials family3, both ZIFs selectively capture carbon dioxide from several different gas mixtures at room temperature, with ZIF-100 capable of storing 28 litres per litre of material at standard temperature and pressure. These characteristics, combined with their high thermal and chemical stability and ease of fabrication, make ZIFs promising candidate materials for strategies aimed at ameliorating increasing atmospheric carbon dioxide levels.

Reticular chemistry of metal-organic polyhedra.

Abstract: Metal-organic polyhedra (MOPs), are discrete metal-organic molecular assemblies. They are useful as host molecules that can provide tailorable internal volume in terms of metrics, functionality, and active metal sites. As a result, these materials are potentially useful for a variety of applications, such as highly selective guest inclusion and gas storage, and as nanoscale reaction vessels. This review identifies the nine most important polyhedra, and describes the design principles for the five polyhedra most likely to result from the assembly of secondary building units, and provides examples of these shapes that are known as metal-organic crystals.

Metal-organic frameworks with high capacity and selectivity for harmful gases

Abstract: Benchmarks have been established for the performance of six metal-organic frameworks (MOFs) and isoreticular MOFs (IRMOFs, which have the same underlying topology as MOF-5), MOF-5, IRMOF-3, MOF-74, MOF-177, MOF-199, and IRMOF-62, as selective adsorbents for eight harmful gases: sulfur dioxide, ammonia, chlorine, tetrahydrothiophene, benzene, dichloromethane, ethylene oxide, and carbon monoxide. Kinetic breakthrough measurements are used to determine the calculated dynamic adsorption capacity of each “benchmark” MOF for each gas. The capacity of each MOF is compared to that of a sample of Calgon BPL activated carbon. We find that pore functionality plays a dominant role in determining the dynamic adsorption performance of MOFs. MOFs featuring reactive functionality outperform BPL carbon in all but one case and exhibit high dynamic adsorption capacities up to 35% by weight.

Covalent organic frameworks as exceptional hydrogen storage materials.

Abstract: We report the H2 uptake properties of six covalent organic frameworks (COFs) from first-principles-based grand canonical Monte-Carlo simulations. The predicted H2 adsorption isotherm is in excellent agreement with the only available experimental result (3.3 vs 3.4 wt % at 50 bar and 77 K for COF-5), also reported here, validating the predictions. We predict that COF-105 and COF-108 lead to a reversible excess H2 uptake of 10.0 wt % at 77 K, making them the best known storage materials for molecular hydrogen at 77 K. We predict that the total H2 uptake for COF-108 is 18.9 wt % at 77 K. COF-102 shows the best volumetric performance, storing 40.4 g/L of H2 at 77 K. These results indicate that the COF systems are most promising candidates for practical hydrogen storage.

Crystals as Molecules: Postsynthesis Covalent Functionalization of Zeolitic Imidazolate Frameworks

Abstract: A new crystalline zeolitic imidazolate framework, ZIF-90, was prepared from zinc(II) nitrate and imidazolate-2-carboxyaldehyde (ICA) and found to have the sodalite-type topology. Its 3D porous framework has an aperture of 3.5 A and a pore size of 11.2 A. The pores are decorated by the aldehyde functionality of ICA which has allowed its transformation to the alcohol functionality by reduction with NaBH4 and its conversion to imine functionality by reaction with ethanolamine to give ZIF-91 and ZIF-92, respectively. The N2 adsorption isotherm of ZIF-90 shows a highly porous material with calculated Langmuir and BET surface areas of 1320 and 1270 m2 g−1. Both functionalized ZIFs retained high crystallinity and in addition ZIF-91 maintained permanent porosity (surface areas: 1070 and 1010 m2 g−1).

Understanding Inflections and Steps in Carbon Dioxide Adsorption Isotherms in Metal-Organic Frameworks

Abstract: Adsorption isotherms for CO2 in IRMOF-1 exhibit inflections that grow into pronounced steps at lower temperatures. The isotherm shapes can be predicted by molecular simulations using a rigid crystal structure, indicating that changes in the MOF crystal structure are not responsible for the steps in this system.

Control of vertex geometry, structure dimensionality, functionality, and pore metrics in the reticular synthesis of crystalline metal-organic frameworks and polyhedra.

Abstract: Metal−organic polyhedra and frameworks (MOPs and MOFs) were prepared by linking square units M2(CO2)4 (M = Cu and Zn) with a variety of organic linkers designed to control the dimensionality (periodicity) and topology of the resulting structures. We describe the preparation, characterization, and crystal structures of 5 new MOPs and 11 new MOFs (termed MOP-14, -15, -17, -23, -24 and MOF-114, -115, -116, -117, -118, -119, -222, -601, -602, -603, -604) and show how their structures are related to the shape and functionality of the building blocks. The gas uptake behaviors of MOP-23 and MOF-601 to -603 are also presented as evidence that these structures have permanent porosity and rigid architectures.

Reticular Synthesis of Covalent Organic Borosilicate Frameworks

Abstract: This paper reports the synthesis and characterization of a new crystalline 3D covalent organic framework, COF-202: [C(C6H4)4]3[B3O6 (tBuSi)2]4, formed from condensation of a divergent boronic acid, tetra(4-dihydroxyborylphenyl)methane, and tert-butylsilane triol, tBuSi(OH)3. This framework is constructed through strong covalent bonds (Si−O, B−O) that link triangular and tetrahedral building units to form a structure based on the carbon nitride topology. COF-202 demonstrates high thermal stability, low density, and high porosity with a surface area of 2690 m2 g−1. The design and synthesis of COF-202 expand the type of linkage that could be used to crystallize new materials with extended covalent organic frameworks.

Amphidynamic Character of Crystalline MOF-5: Rotational Dynamics of Terephthalate Phenylenes in a Free-Volume, Sterically Unhindered Environment

Abstract: Metal−organic frameworks (MOFs) have been the focus of much interest within the context of hydrogen storage and other materials applications. With static metal clusters linked by axially substituted organic spacers capable of experiencing internal rotations, MOFs are one of the most promising amphidynamic materials to investigate and exploit the dynamics of crystalline solids. In this communication we report an experimental study of the rotational dynamics of the 1,4-phenylenedicarboxylate bridge of MOF-5, which has no steric contacts that might contribute to the rotational barrier. Highly reproducible 1H T1 relaxation, high-resolution 13C CPMAS, and variable temperature quadrupolar echo 2H NMR data were obtained from high quality samples that were sealed at reduced pressure (ca. 3 mTorr). 2H NMR line shape simulation revealed an activation barrier for rotation of 11.3 ± 2.0 kcal/mol, which is lower than the 14−16 kcal/mol values reported in theoretical studies of truncated models. While our results sugge...

Preparation of functionalized zeolitic frameworks

Abstract: The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

Adsorptive gas separation of multi-component gases

Abstract: The disclosure relates generally to a gas-separation system for separating one or more components from a multi-component gas using Zeolitic imidazolate or imidazolate-derived framework.

Crystalline 3d- and 2d-covalent organic frameworks

Abstract: The disclosure relates generally to materials that comprise organic frameworks. The disclosure also relates to materials that are useful to store and separate gas molecules and sensors.

Edible and biocompatible metal-organic frameworks

Abstract: The disclosure relates generally to materials that comprise organic frameworks. The disclosure also relates to materials that are useful to store and separate biological agents that are environmentally friendly and biocompatible.

Room Temperature Synthesis of Metal-Organic Frameworks: MOF-5, MOF-74, MOF-177, MOF-199, and IRMOF-0.

Abstract: Room temperature synthesis of metal-organic frameworks (MOFs) has been developed for four well-known MOFs: MOF-5, MOF-74, MOF-177, and MOF-199. A new isoreticular metal framework (IRMOF), IRMOF-0, having the same cubic topology as MOF-5, has been synthesized from acetylenedicarboxylic acid using this method to accommodate the thermal sensitivity of the linker. Despite acetylenedicarboxylate being the shortest straight linker that can be made into an IRMOF, IRMOF-0 forms as a doubly interpenetrating structure, owing to the rod-like nature of the linker.

Reticular Chemistry of Metal—Organic Polyhedra

Abstract: Metal-organic polyhedra (MOPs), are discrete metal-organic molecular assemblies. They are useful as host molecules that can provide tailorable internal volume in terms of metrics, functionality, and active metal sites. As a result, these materials are potentially useful for a variety of applications, such as highly selective guest inclusion and gas storage, and as nanoscale reaction vessels. This review identifies the nine most important polyhedra, and describes the design principles for the five polyhedra most likely to result from the assembly of secondary building units, and provides examples of these shapes that are known as metal-organic crystals.

Chemistry and Applications of Porous Metal–Organic Frameworks

Abstract: The sections in this article are Introduction Terminology and Structure Synthesis Characterization Emerging Applications Adsorption Properties Diffusional Properties Gas Purification Gas Separation Gas Storage Catalysis Conclusions Keywords: porous metal–organic frameworks; bridging ligands; nanoporous host materials; thermal and mechanical stability

Séparation de gaz d'adsorption de gaz multi-composants

Abstract: L'invention concerne de maniere generale un systeme de separation de gaz pour separer un ou plusieurs composants d'un gaz multi-composants en utilisant un imidazolate zeolitique ou une structure derivee d'un imidazolate.

Préparation de structures zéolithiques fonctionnalisées

Abstract: L'invention concerne des structures zeolithiques pour la separation des gaz, le stockage des gaz, la catalyse et les detecteurs. Plus particulierement, l'invention concerne des structures zeolithiques (ZIF). Les ZIF de la presente invention comprennent un certain nombre de metaux de transition ou une composition homogene de metaux de transition.