263 research outputs found

    Reticular Chemistry in All Dimensions.

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    The Development of Global Science.

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    How do we build research capacity throughout the world and capture the great human potential? To us, the answer is rather straightforward: the time-honored tradition of scientific mentoring must be practiced on a wider scale across borders. Herein, we detail the necessity for expanding mentorship to a global scale and provide several important principles to be considered when designing, planning, and implementing programs and centers of research around the world

    Precise Control of Molecular Self-Diffusion in Isoreticular and Multivariate Metal-Organic Frameworks.

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    Understanding the factors that affect self-diffusion in isoreticular and multivariate (MTV) MOFs is key to their application in drug delivery, separations, and heterogeneous catalysis. Here, we measure the apparent self-diffusion of solvents saturated within the pores of large single crystals of MOF-5, IRMOF-3 (amino-functionalized MOF-5), and 17 MTV-MOF-5/IRMOF-3 materials at various mole fractions. We find that the apparent self-diffusion coefficient of N,N-dimethylformamide (DMF) may be tuned linearly between the diffusion coefficients of MOF-5 and IRMOF-3 as a function of the linker mole fraction. We compare a series of solvents at saturation in MOF-5 and IRMOF-3 to elucidate the mechanism by which the linker amino groups tune molecular diffusion. The ratio of the self-diffusion coefficients for solvents in MOF-5 to those in IRMOF-3 is similar across all solvents tested, regardless of solvent polarity. We conclude that average pore aperture, not solvent-linker chemical interactions, is the primary factor responsible for the different diffusion dynamics upon introduction of an amino group to the linker

    Metal-organic and zeolite imidazolate frameworks (MOFs and ZIFs) for highly selective separations

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    Metal-organic and zeolite imidazolate frameworks (MOFs and ZIFs) have been investigated for the realization as separation media with high selectivity. These structures are held together with strong bonds, making them architecturally, chemically, and thermally stable. Therefore, employing well designed building units, it is possible to discover promising materials for gas and vapor separation. This grant was focused on the study of MOFs and ZIFs with these specific objectives: (i) to develop a strategy for producing MOFs and ZIFs that combine high surface areas with active sites for their use in gas adsorption and separation of small organic compounds, (ii) to introduce active sites in the framework by a post-synthetic modification and metalation of MOFs and ZIFs, and (iii) to design and synthesize MOFs with extremely high surface areas and large pore volumes to accommodate large amounts of guest molecules. By the systematic study, this effort demonstrated how to introduce active functional groups in the frameworks, and this is also the origin of a new strategy, which is termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. One of the solutions to overcome this challenge is an isoreticular expansion of a MOFÃÂÃÂÃÂâÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs structure. With triangular organic linker and square building units, we demonstrated that MOF-399 has a unit cell volume 17 times larger than that of the first reported material isoreticular to it, and it has the highest porosity (94%) and lowest density (0.126 g cm-3) of any MOF reported to date. MOFs are not just low density materials; the guest-free form of MOF-210 demonstrates an ultrahigh porosity, whose BET surface area was estimated to be 6240 m2 g-1 by N2 adsorption measurements

    Design and synthesis of an exceptionally stable and highly porous metal-organic framework

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    Open metal-organic frameworks are widely regarded as promising materials for applications(1-15) in catalysis, separation, gas storage and molecular recognition. Compared to conventionally used microporous inorganic materials such as zeolites, these organic structures have the potential for more flexible rational design, through control of the architecture and functionalization of the pores. So far, the inability of these open frameworks to support permanent porosity and to avoid collapsing in the absence of guest molecules, such as solvents, has hindered further progress in the field(14,15). Here we report the synthesis of a metal-organic framework which remains crystalline, as evidenced by Xray single-crystal analyses, and stable when fully desolvated and when heated up to 300 degrees C. This synthesis is achieved by borrowing ideas from metal carboxylate cluster chemistry, where an organic dicarboxylate linker is used in a reaction that gives supertetrahedron clusters when capped with monocarboxylates. The rigid and divergent character of the added linker allows the articulation of the dusters into a three-dimensional framework resulting in a structure with higher apparent surface area and pore volume than most porous crystalline zeolites. This simple and potentially universal design strategy is currently being pursued in the synthesis of new phases and composites, and for gas-storage applications.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62847/1/402276a0.pd

    Three‐periodic nets and tilings: regular and quasiregular nets

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115935/1/S0108767302018494.pd

    Three‐periodic nets and tilings: semiregular nets

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115982/1/S0108767303017100.pd

    Adsorption Mechanism and Uptake of Methane in Covalent Organic Frameworks: Theory and Experiment

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    We determined the methane (CH_4) uptake (at 298 K and 1 to 100 bar pressure) for a variety of covalent organic frameworks (COFs), including both two-dimensional (COF-1, COF-5, COF-6, COF-8, and COF-10) and three-dimensional (COF-102, COF-103, COF-105, and COF-108) systems. For all COFs, the CH_4 uptake was predicted from grand canonical Monte Carlo (GCMC) simulations based on force fields (FF) developed to fit accurate quantum mechanics (QM) [second order Møller−Plesset (MP2) perturbation theory using doubly polarized quadruple-ζ (QZVPP) basis sets]. This FF was validated by comparison with the equation of state for CH_4 and by comparison with the experimental uptake isotherms at 298 K (reported here for COF-5 and COF-8), which agrees well (within 2% for 1−100 bar) with the GCMC simulations. From our simulations we have been able to observe, for the first time, multilayer formation coexisting with a pore filling mechanism. The best COF in terms of total volume of CH_4 per unit volume COF absorbent is COF-1, which can store 195 v/v at 298 K and 30 bar, exceeding the U.S. Department of Energy target for CH_4 storage of 180 v/v at 298 K and 35 bar. The best COFs on a delivery amount basis (volume adsorbed from 5 to 100 bar) are COF-102 and COF-103 with values of 230 and 234 v(STP: 298 K, 1.01 bar)/v, respectively, making these promising materials for practical methane storage

    Three‐periodic nets and tilings: minimal nets

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116005/1/S0108767304015442.pd
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