[show abstract][hide abstract] ABSTRACT: Because of their high surface areas, crystallinity, and tunable properties, metal−organic frameworks (MOFs) have attracted intense interest as next-generation materials for gas capture and storage. While much effort has been devoted to the discovery of new MOFs, a vast catalog of existing MOFs resides within the Cambridge Structural Database (CSD), many of whose gas uptake properties have not been assessed. Here we employ data mining and automated structure analysis to identify, "cleanup," and rapidly predict the hydrogen storage properties of these compounds. Approximately 20 000 candidate compounds were generated from the CSD using an algorithm that removes solvent/guest molecules. These compounds were then characterized with respect to their surface area and porosity. Employing the empirical relationship between excess H 2 uptake and surface area, we predict the theoretical total hydrogen storage capacity for the subset of ∼4000 compounds exhibiting nontrivial internal porosity. Our screening identifies several overlooked compounds having high theoretical capacities; these compounds are suggested as targets of opportunity for additional experimental characterization. More importantly, screening reveals that the relationship between gravimetric and volumetric H 2 density is concave downward, with maximal volumetric performance occurring for surface areas of 3100−4800 m 2 /g. We conclude that H 2 storage in MOFs will not benefit from further improvements in surface area alone. Rather, discovery efforts should aim to achieve moderate mass densities and surface areas simultaneously, while ensuring framework stability upon solvent removal.
Chemistry of Materials 07/2013; 25(16):3373. · 8.24 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper describes the heterogenization of single-site transition-metal catalysts in metal-organic frameworks (MOFs) via cation exchange. A variety of cationic complexes of Pd, Fe, Ir, Rh, and Ru have been incorporated into ZJU-28, and the new materials have been characterized by optical microscopy, inductively coupled plasma optical emission spectroscopy, and powder X-ray diffraction. MOF-supported [Rh(dppe)(COD)]BF4 catalyzes the hydrogenation of 1-octene to n-octane. The activity of this supported catalyst compares favorably to its homogeneous counterpart, and it can be recycled at least four times. Overall, this work provides a new and general approach for supporting transition-metal catalysts in MOFs.
Journal of the American Chemical Society 07/2013; · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Microporous coordination polymers (MCPs) have emerged as strong contenders for adsorption-based fuel storage and delivery in large part because of their high specific surface areas. The strategy of increasing surface area by increasing organic linker length has shown only sporadic success; as demonstrated by many members of the iconic Zn4O-based IRMOF series, for example, accessible porosity is often limited by interpenetration or pore collapse upon guest removal. In this work, we focus on Zn4O(ndc)3 (IRMOF-8, ndc = 2,6-naphthalene dicarboxylate), which exhibits typical surface areas of only 1000-2000 m(2)/g even though a surface area of more than 4000 m(2)/g is expected from geometric analysis of the originally reported crystal structure. We recently showed that a high surface area could be produced with zinc and ndc by room-temperature synthesis followed by activation with flowing supercritical CO2. In this work, we investigate in detail the porosity of both the low- and high-surface-area materials. Positron annihilation lifetime spectroscopy (PALS) is used to show that the low-surface-area material suffers from near-complete interpenetration, explaining why traditional synthetic routes have failed to yield materials with the expected porosity. Furthermore, the high-pressure hydrogen and methane sorption properties of noninterpenetrated Zn4O(ndc)3 are examined, and PALS is used to show that pore filling is not operative during room-temperature CH4 sorption even at pressures approaching 100 bar. These results provide insight into how gas adsorbs in high-surface-area materials at high pressure and reinforce previous contentions that increasing surface area alone is not sufficient for the simultaneous optimization of deliverable gravimetric and volumetric gas uptake in MCPs.
[show abstract][hide abstract] ABSTRACT: Positronium (Ps) is shown to exist in a delocalized state in self-assembled metalorganic crystals that have large 1.3-1.5 nm cell sizes. Belonging to a class of materials with record high accessible specific surface areas, these highly porous crystals are the first to allow direct probing with simple annihilation lifetime techniques of the transport properties of long-lived triplet Ps in what is hypothesized to be a Bloch state. Delocalized Ps has unprecedented (high) Ps mobility driven primarily by weak phonon scattering with unusual and profound consequences on how Ps probes the lattice.
[show abstract][hide abstract] ABSTRACT: Flowing supercritical CO(2) was used to activate a cross section of microporous coordination polymers (MCPs) directly from DMF, thus avoiding exchange with a volatile solvent. Most MCPs displayed exceptional surface areas directly after treatment although those with coordinatively unsaturated metals benefit from heating. The method presents an advance in efficiency of activation and quality of material obtained.
Chemical Communications 01/2013; · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: The synthesis and successful activation of IRMOF-8 (Zn(4)O(ndc)(3), ndc = naphthalene-2,6-dicarboxylate) is presented. Room temperature synthesis effectively suppresses interpenetration. Although conventional activation under reduced pressure leads to structural collapse, activation by flowing supercritical CO(2) yields a guest-free material with a BET surface area of 4461 m(2) g(-1).
Chemical Communications 08/2012; 48(79):9828-30. · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although a multitude of microporous coordination polymers (MCPs) with ultrahigh surface area have been reported in the last decade, none of these can come close to matching the cost/performance ratio of conventional sorbents such as zeolites and carbons for most applications. There is a need to drastically reduce the cost of MCPs and this goal cannot be achieved through complex linker synthesis strategies so often used to boost MCP performance. Here two new MCPs: UMCM-8 (Zn4O(benzene-1,4-dicarboxylate)1.5(naphthalene-2,6-dicarboxylate)1.5), and UMCM-9 (Zn4O(naphthalene-2,6-dicarboxylate)1.5(biphenyl-4,4′-dicarboxylate)1.5) are described and the concept of using mixtures of readily available linear linkers that enforce different spacings between network nodes is introduced as a means to reduce interpenetration. These new MCPs demonstrate Brunauer–Emmett–Teller (BET) surface areas over 4000 m2 g−1 and high pore volumes over 1.80 cm3 g−1.
Chemical Science 05/2012; 3(8):2429-2432. · 8.31 Impact Factor
[show abstract][hide abstract] ABSTRACT: High reversibility during crystallization leads to relatively defect-free crystals through repair of nonperiodic inclusions, including those derived from impurities. Microporous coordination polymers (MCPs) can achieve a high level of crystallinity through a related mechanism whereby coordination defects are repaired, leading to single crystals. In this work, we discovered and exploited the fact that this process is far from perfect for MCPs and that a minority ligand that is coordinatively identical to but distinct in shape from the majority linker can be inserted into the framework, resulting in defects. The reaction of Zn(II) with 1,4-benzenedicarboxylic acid (H(2)BDC) in the presence of small amounts of 1,3,5-tris(4-carboxyphenyl)benzene (H(3)BTB) leads to a new crystalline material, MOF-5(O(h)), that is nearly identical to MOF-5 but has an octahedral morphology and a number of defect sites that are uniquely functionalized with dangling carboxylates. The reaction with Pd(OAc)(2) impregnates the metal ions, creating a heterogeneous catalyst with ultrahigh surface area. The Pd(II)-catalyzed phenylation of naphthalene within Pd-impregnated MOF-5(O(h)) demonstrates the potential utility of an MCP framework for modulating the reactivity and selectivity of such transformations. Furthermore, this novel synthetic approach can be applied to different MCPs and will provide scaffolds functionalized with catalytically active metal species.
Journal of the American Chemical Society 11/2011; 133(50):20138-41. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: The CO(2)-capture performance of microporous coordination polymers of the M/DOBDC series (where M = Zn, Ni, Co, and Mg; DOBDC = 2,5-dioxidobenzene-1,4-dicarboxylate) was evaluated under flow-through conditions with dry surrogate flue gas (5/1 N(2)/CO(2)). The CO(2) capacities were found to track with static CO(2) sorption capacities at room temperature, with Mg/DOBDC demonstrating an exceptional capacity for CO(2) (23.6 wt %). The effect of humidity on the performance of Mg/DOBDC was investigated by collecting N(2)/CO(2)/H(2)O breakthrough curves at relative humidities (RHs) in the feed of 9, 36, and 70%. After exposure at 70% RH and subsequent thermal regeneration, only about 16% of the initial CO(2) capacity of Mg/DOBDC was recovered. However, in the case of Ni/DOBDC and Co/DOBDC, approximately 60 and 85%, respectively, of the initial capacities were recovered after the same treatment. These data indicate that although Mg/DOBDC has the highest capacity for CO(2), under the conditions used in this study, Co/DOBDC may be a more desirable material for deployment in CO(2) capture systems because of the added costs associated with flue gas dehumidification.
[show abstract][hide abstract] ABSTRACT: N-Heteroarene substitution into biphenyl-based linkers enhances the uptake of electron-rich organosulfur molecules in a series of isostructural microporous coordination polymers.
Chemical Communications 02/2011; 47(5):1452-4. · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: Five non-interpenetrated microporous coordination polymers (MCPs) are derived by vertex desymmetrization using linkers with symmetry inequivalent coordinating groups, and these MCPs include properties such as rare metal clusters, new network topologies, and supramolecular isomerism. Gas sorption in polymorphic frameworks, UMCM-152 and UMCM-153 (based upon a copper-coordinated tetracarboxylated triphenylbenzene linker), reveals nearly identical properties with BET surface areas in the range of 3300-3500 m(2)/g and excess hydrogen uptake of 5.7 and 5.8 wt % at 77 K. In contrast, adsorption of organosulfur compounds dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) shows remarkably different capacities, providing direct evidence that liquid-phase adsorption is not solely dependent on surface area or linker/metal cluster identity. Structural features present in MCPs derived from these reduced symmetry linkers include the presence of more than one type of Cu-paddlewheel in a structure derived from a terphenyl tricarboxylate (UMCM-151) and a three-bladed zinc paddlewheel metal cluster in an MCP derived from a pentacarboxylated triphenylbenzene linker (UMCM-154).
Journal of the American Chemical Society 10/2010; 132(39):13941-8. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Isolated successes of coordination copolymerization for the production of microporous coordination polymers (MCPs) have been reported recently; the logic for this synthetic approach has not been established nor have the key features of the synthetic conditions needed to generalize the method. Here, we establish guidelines for application of the copolymerization technique by exploring coordination modes and report, in addition to details on two previous coordination copolymers with exceptional properties, three new MCPs: UMCM-3 (Zn(4)O(2,5-thiophenedicaboxylate)(1.2)(1,3,5-tris(4-carboxyphenyl)benzene)(1.2)), UMCM-4 (Zn(4)O(1,4-benzenedicarboxylate)((3)/(2))(4,4',4''-tricarboxytriphenylamine)), and UMCM-5 (Zn(4)O(1,4-naphthalenedicarboxylate)(1,3,5-tris(4-carboxyphenyl)benzene)((4)/(3))). The MCPs prepared by the copolymerization technique demonstrate Brunauer-Emmett-Teller (BET) surface areas between 3500-5200 m(2)/g and high pore volumes (1.64-2.37 cm(3)/g). In addition, the alignment of poly(3-hexylthiophene) within mesoporous channels of UMCM-1 is reported as a demonstration of the unique properties of these hosts.
Journal of the American Chemical Society 10/2010; 132(42):15005-10. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Reacting biphenyl-3,4',5-tricarboxylic acid (H(3)BHTC) with the appropriate metal salt yields the microporous coordination polymers (MCPs) Mn(3)(BHTC)(2) (1), Mg(3)(BHTC)(2) (2), and Co(3)(BHTC)(2) (3) containing hourglass metal clusters. The addition of Cu to reactions with Co(II), Fe(III), or Mn(II) leads to the formation of heterobimetallic UMCM-150 isostructural analogues Co(1)Cu(2)(BHTC)(2) (4), Fe(1)Cu(2)(BHTC)(2) (5), and Mn(1)Cu(2)(BHTC)(2) (6) containing both paddlewheel and trinuclear metal clusters. X-ray diffraction analysis of the crystals of the heterobimetallic MCPs suggests that Cu on the trinuclear site of UMCM-150 was replaced by the other metal, whereas Cu in paddlewheel sites remains unchanged. N(2) sorption isotherms were measured for the mixed-metal UMCM-150 analogues, and it was confirmed that there is no structural collapse after the metal replacement.
[show abstract][hide abstract] ABSTRACT: Mixing two different linkers with the same topology has been applied to make metal-organic frameworks (MOFs) either in one batch or sequentially to generate coordination copolymers with either a randomly mixed or a core-shell composition of linkers.
Chemical Communications 11/2009; · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: We evaluate the potential of microporous coordination polymers (MCPs) to act as the stationary phase in liquid chromatographic separations. MCPs derived from carboxylates coordinated to copper (HKUST-1) and zinc (MOF-5) were studied. The shape and size selective separation of organic compounds including benzene, ethylbenzene, styrene, naphthalene, anthracene, phenanthrene, pyrene, 1,3,5-triphenylbenzene, and 1,3,5-tris(4-bromophenyl)benzene was performed, and in most cases excellent separation was achieved based on a combination of molecular sieving and adsorption effects.
[show abstract][hide abstract] ABSTRACT: Microporous coordination polymers (MCPs) are demonstrated to be efficient adsorbents for the removal of the organosulfur compounds dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) from model diesel fuel and diesel fuel. For example, packed bed breakthrough experiments utilizing UMCM-150 find capacities of 25.1 g S/kg MCP for DBT and 24.3 g S/kg MCP for DMDBT from authentic diesel indicating that large amounts of fuel are desulfurized before the breakthrough point. Unlike activated carbons, where selectivity has been a problem, MCPs selectively adsorb the organosulfur compounds over other, similar components of diesel. Complete regeneration using toluene at modest temperatures is achieved. The attainment of high selectivities and capacities, particularly for the adsorption of the refractory compounds that are difficult to remove using current desulfurization techniques, in a reversible sorbent indicates that fuel desulfurization may be an important application for MCPs.
Journal of the American Chemical Society 09/2009; 131(40):14538-43. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: New levels of surface area are achieved in a coordination polymer (UMCM-2, University of Michigan Crystalline Material) derived from zinc-mediated coordination copolymerization of a dicarboxylic and tricarboxylic acid. In addition to a large micropore contribution to the surface area, mesopores are also present. In contrast to the recently reported coordination copolymer UMCM-1, which has a mesoporous channel, UMCM-2 is built from three types of cages. In spite of exceptional porosity, both of these coordination polymers are thermally robust. Hydrogen uptake performance of UMCM-2 approaches 7 wt% at 77 K.
Journal of the American Chemical Society 05/2009; 131(12):4184-5. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: The first Be-based microporous coordination polymer is shown to have a surface area of 3500 m2/g (BET) and a maximum excess H2 uptake of 53 mg/g at 24 bar and 77 K.
Journal of Materials Chemistry 01/2009; 19(36). · 5.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: The combination of zinc(II) nitrate with 1,3,5-(triscarboxyphenyl)benzene (H 3BTB) leads to five different microporous coordination polymers (MCPs). Two of these were previously known (MOF-177 and MOF-39), whereas polymer-induced heteronucleation was used in the discovery of three phases that have not been previously reported ( Zn/BTB ant, Zn/BTB tsx, and Zn/BTB dia). Modification of crystallization conditions allows for the bulk-scale synthesis of each of these MCPs. Zn/BTB ant and Zn/BTB tsx are each interpentrated 6,3-connected nets composed of the basic zinc carboxylate secondary building unit (SBU) and the tritopic linker BTB. The underlying noninterpenetrated net of Zn/BTB ant is derived for the net of anatase, whereas that of Zn/BTB tsx is the previously unreported "tsx" framework. Zn/BTB dia consists of an underlying diamondoid net in which four linear, trinuclear zinc hourglass SBUs are arranged about a central mu 4-oxo anion as the tetrahedral unit in the net and BTB further links the hourglass SBUs. Zn/BTB ant, Zn/BTB tsx, and MOF-177 are here defined as polymorphic frameworks in that each is composed of the same SBU and linker but differ in topology and thus pore structure. These frameworks may be called a polyreticular series by analogy to several reported isoreticular series. The effect of linker-linker interactions are discussed.