We show that metal-organic frameworks (MOFs) can incorporate a large number of different functionalities on linking groups in a way that mixes the linker, rather than forming separate domains. We ...made complex MOFs from 1,4-benzenedicarboxylate (denoted by "A" in this work) and its derivatives -NH₂, -Br, -(Cl)₂, -NO₂, -(CH₃)₂, -C₄H₄, -(OC₃H₅)₂, and -(OC₇H₇)₂ (denoted by "B" to "I," respectively) to synthesize 18 multivariate (MTV) MOF-5 type structures that contain up to eight distinct functionalities in one phase. The backbone (zinc oxide and phenylene units) of these structures is ordered, but the distribution of functional groups is disordered. The complex arrangements of several functional groups within the pores can lead to properties that are not simply linear sums of those of the pure components. For example, a member of this series, MTV-MOF-5-EHI, exhibits up to 400% better selectivity for carbon dioxide over carbon monoxide compared with its best same-link counterparts.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Zeolites are one of humanity’s most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in ...petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si−O−Si preferred angle in zeolites (145°) is coincident with that of the bridging angle in the M−Im−M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link−link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the capture of CO2 and its selective separation from industrially relevant gas mixtures. Currently, ZIFs are the best porous materials for the selective capture of CO2; furthermore, they show exceptionally high capacity for CO2 among adsorbents operating by physisorption. The stability of ZIFs has also enabled organic transformations to be carried out on the crystals, yielding covalently functionalized isoreticular structures wherein the topology, crystallinity, and porosity of the ZIF structure are maintained throughout the reaction process. These reactions, being carried out on macroscopic crystals that behave as single molecules, have enabled the realization of the chemist’s dream of using “crystals as molecules”, opening the way for the application of the extensive library of organic reactions to the functionalization of useful extended porous structures.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
3.
Hydrogen Storage in New Metal–Organic Frameworks Tranchemontagne, David J; Park, Kyo Sung; Furukawa, Hiroyasu ...
Journal of physical chemistry. C,
06/2012, Volume:
116, Issue:
24
Journal Article
Peer reviewed
Five new metal–organic frameworks (MOFs, termed MOF-324, 325, 326 and IRMOF-61 and 62) of either short linkers (pyrazolecarboxylate and pyrazaboledicarboxylate) or long and thin alkyne ...functionalities (ethynyldibenzoate and butadiynedibenzoate) were prepared to examine their impact on hydrogen storage in MOFs. These compounds were characterized by single-crystal X-ray diffraction, and their low-pressure and high-pressure hydrogen uptake properties were investigated. In particular, volumetric excess H2 uptake by MOF-324 and IRMOF-62 outperforms MOF-177 up to 30 bar. Inelastic neutron-scattering studies for MOF-324 also revealed strong interactions between the organic links and hydrogen, in contrast to MOF-5 where the interactions between the Zn4O unit and hydrogen are the strongest. These data also show that smaller pores and polarized linkers in MOFs are indeed advantageous for hydrogen storage.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A catalytic system combining the high activity of homogeneous catalysts and the ease of use of heterogeneous catalysts for methane activation is reported. The vanadium-containing metal–organic ...frameworks (MOFs) MIL-47 and MOF-48 are found to have high catalytic activity and chemical stability. They convert methane selectively to acetic acid with 70% yield (490 TON) based on K2S2O8 as an oxidant. Isotopic labeling experiments showed that two methane molecules are converted to the produced acetic acid. The MOF catalysts are reusable and remain catalytically active for several recycling steps without losing their crystalline structures.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
5.
Docking in Metal-Organic Frameworks Li, Qiaowei; Zhang, Wenyu; Miljanić, Ognjen Š ...
Science (American Association for the Advancement of Science),
08/2009, Volume:
325, Issue:
5942
Journal Article
Peer reviewed
Open access
The use of metal-organic frameworks (MOFs) so far has largely relied on nonspecific binding interactions to host small molecular guests. We used long organic struts (approximately 2 nanometers) ...incorporating 34- and 36-membered macrocyclic polyethers as recognition modules in the construction of several crystalline primitive cubic frameworks that engage in specific binding in a way not observed in passive, open reticulated geometries. MOF-1001 is capable of docking paraquat dication (PQT²⁺) guests within the macrocycles in a stereoelectronically controlled fashion. This act of specific complexation yields quantitatively the corresponding MOF-1001 pseudorotaxanes, as confirmed by x-ray diffraction and by solid- and solution-state nuclear magnetic resonance spectroscopic studies performed on MOF-1001, its pseudorotaxanes, and their molecular strut precursors. A control experiment involving the attempted inclusion of PQT²⁺ inside a framework (MOF-177) devoid of polyether struts showed negligible uptake of PQT²⁺, indicating the importance of the macrocyclic polyether in PQT²⁺ docking.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Two imidazolate−metal based rhombic dodecahedra (termed MOP-100 and MOP-101) were designed and prepared from (NH3)4Pd(NO3)2 and hydrogen tetrakis(1-imidazolyl)borate or hydrogen ...tetrakis(4-methyl-1-imidazolyl)borate in a concentrated ammonium hydroxide solution at 85 °C. Both rhombic dodecahedra show unusual chemical stability in acidic and basic solutions as well as common organic solvents. Permanent porosity was examined by gas adsorption studies. From the N2 isotherm for MOP-101, the Langmuir and BET surface areas of MOP-101 were calculated to be 350 and 280 m2 g−1, respectively. Anion exchange experiments confirmed the internal cavities of such polyhedra are accessible.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A metal-organic framework was constructed from struts in which donor-acceptor 2catenane units become integrated, leading to a high density of these molecular machinery modules positioned precisely in ...well-defined layered (2D) structures.
The triborate and pentaborate compounds 3-hydroxy-2,2-dimethylpropylammonium triborate(1+), HOCH2C(CH3)2NH3B3O3(OH)4 (1), and 2-hydroxyethylammonium pentaborate(1−), HOCH2CH2NH3B5O6(OH)4·H2O (2), ...were prepared by crystallization from concentrated aqueous boric acid solutions containing the respective alcoholamines at a boric acid−alcoholamine mole ratio of 3.33:1.00. Compound 1 crystallized in the triclinic space group P1̅ with a = 5.9595(9) Å, b = 6.3024(9) Å, c = 15.594(2) Å, α = 91.218(2)°, β = 91.138(2)°, γ = 118.034(2)°, V = 516.56(13) Å3, and Z = 2; 2 crystallized in the monoclinic space group P21/n with a = 11.2469(8) Å, b = 9.5091(6) Å, c = 11.5422(8) Å, β = 90.175(1)°, V = 1234.41(15) Å3, and Z = 4. Compound 1 contains a rare example of a structurally characterized hydroxyl-hydrated triborate monoanion. Comparisons are made with other known examples of this anion.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Several unique crystalline zinc borates are known, a few of which find industrial use in significant tonnages. Although the most important of these has been a commercial product for more than 3 ...decades, it was never before structurally characterized. The structure of ZnB3O4(OH)3 (1) was determined for the first time by single-crystal X-ray diffraction, revealing it to be a complex network consisting of infinite polytriborate chains cross-linked by coordination with zinc and further integrated by hydrogen bonding. The structure of 1 bears similarities to certain borate minerals, most notably, studenitsite (CaB3O4(OH)3) and colemanite (CaB3O4(OH)3·H2O); however, significant differences are described. Hydrolytic and thermochemical properties of 1 are discussed. This compound illustrates the important role played by metal cations in directing the spatial arrangement of anionic polyborate structural units in metal borates. This new structural information leads to a revision in the chemical formula, 2ZnO·3B2O3·3.5H2O, typically used to describe this material as an article of commerce, to 2ZnO·3B2O3·3H2O. Compound 1 crystallizes in the monoclinic space group P21/n with a = 6.845(2) Å, b = 9.798(2) Å, c = 7.697(2) Å, β = 106.966(4)°, V = 493.8 (2) Å3, and Z = 4.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A series of crystalline nonmetal borate compounds was prepared by reactions of linear α,ω-diaminoalkanes, H2N(CH2) n NH2 (n = 5−12), with excess boric acid in aqueous solution. These simple reagents ...self-assemble in water to form complex ordered structures. The products were characterized by a combination of elemental, thermal, and X-ray diffraction analyses as well as single-crystal X-ray diffraction studies. In each case except for n = 7 and 12, a bis(pentaborate) product of general formula H3N(CH2) n NH3B5O6(OH)42 (1, 2, 4−7) was obtained in good yield. When n = 12, the product, H3N(CH2)12NH3B5O6(OH)42·4H2O (8), contained interstitial water. When n = 7, a product of composition H3N(CH2) 7 NH3B8O10(OH)6·2B(OH)3 (3) was obtained, containing an unusual octaborate anion and interstitial boric acid. The borate anions form hydrogen-bonded supramolecular anionic frameworks that host alkyldiammonium dications. These cations contribute to hydrogen bonding and arrange either extended linearly or folded to varying degrees across channels. This study reveals an interplay between the anionic borate host and the cationic guest in which the nature of the cation controls the borate framework structure, which in turn influences cation conformation.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
PDF
