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This paper describes the systematic study of metal–organic framework (MOF) catalysts for the reaction of propylene oxide (PO) with carbon dioxide (CO2) to generate propylene carbonate (PC). These studies began with the evaluation of MIL-101(Cr) as catalyst in a flow reactor. Under the developed flow conditions, MIL-101(Cr) was found to effectively catalyze PO carbonation in the absence of a halide co-catalyst. A systematic study of catalyst performance was then undertaken as a function of MOF synthesis technique, activation conditions, metal center, and node architecture. Ultimately, these investigations led to the identification of MIL-100(Sc) as a new, active, and stable catalyst for PO carbonation.

Exploratory research into the critical steps in metal-organic framework (MOF) activation involving solvent exchange and solvent evacuation are reported. It is discovered that solvent exchange kinetics are extremely fast, and minutes rather days are appropriate for solvent exchange in many MOFs. It is also demonstrated that choice of a very low surface tension solvent is critical in successfully activating challenging MOFs. MOFs that have failed to be activated previously can achieve predicted surface areas provided that lower surface tension solvents, such as n-hexane and perfluoropentane, are applied. The insights herein aid in the efficient activation of MOFs in both laboratory and industrial settings and provide best practices for avoiding structural collapse.

The cationic rhodium complexes (dppe)Rh(COD)BF4 and (MeCN)2Rh(COD)BF4 have been supported in metal–organic frameworks bearing anionic nodes (ZJU-28) and anionic linkers (MIL-101-SO3) via ion exchange. These MOF-supported Rh species serve as recyclable catalysts for the hydrogenation of both the terminal alkene substrate 1-octene and the internal alkene substrate 2,3-dimethylbutene. The nature of the MOF support impacts various aspects of catalysis, including: (i) the rate of 1-octene hydrogenation, (ii) the activity and recyclability of the catalyst in 2,3-dimethylbutene hydrogenation, and (iii) the size selectivity of hydrogenation with alkene substrates appended to calixarenes.

Examination of the microstructure of metal–organic frameworks (MOFs) after postsynthetic exchange (PSE) reveals that the exchanged ligand is concentrated at the edges of the crystal and decreases in concentration with crystal depth, resulting in a core–shell arrangement. Diffusion studies of the carboxylate ligand into MOF-5 indicate that diffusion is limiting to the exchange process and may ultimately be responsible for the observed core–shell structure. Examination of PSE in UMCM-8 and single crystals of UiO-66 shows a similar trend, illustrating the applicability of PSE as a method for the creation of core–shell MOFs.

The application of a core-shell architecture allows the formation of a polymer-coated metal-organic framework (MOF) maintaining high surface area (2289-2857 m(2) g(-1)). The growth of a MOF shell from a MOF core was used to spatially localize initiators by post-synthetic modification. The confinement of initiators ensures that polymerization is restricted to the outer shell of the MOF.

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.

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).

Porous crystals constructed from the assembly of organic linking units with metal ions or metal clusters are proving to be an exciting class of materials with unprecedented properties and high potential for use in applications such as catalysis, gas storage, and separations. The underlying structure obtained from a given secondary building unit (SBU) with a multitopic ligand can be analyzed, at least with hindsight, as belonging to various nets. In some cases this approach has led to well-defined series with preserved topologies whose members vary in metrics or functionalities. At the same time, it is clear that even a single linker with a given metal under the same reaction conditions can give rise to considerable structural diversity, as is illustrated by our recent application of polymer-induced heteronucleation to the discovery of three new phases based on the simple terephthalic acid linker/zinc nitrate system. Perhaps one lesson to be learned is that there is currently no single structure-predicting design scheme but rather sets of empirically derived default behaviors that can often be used to rationalize the outcome of an experiment. In the case of employing two different linkers possessing the same coordinating functionality, experimental data are lacking, and there is no basis for answering even the most basic question of phase composition. In broad terms we can expect two different behaviors in a crystalline mixed-linker coordination polymer. The default behavior for two components combined and allowed to crystallize is segregation; this behavior forms the basis of purification by crystallization. By contrast, the default behavior when monomers of similar reactivity are combined is random copolymerization. Therefore, it is interesting to contemplate whether in a porous crystal in which strong bonds reversibly assemble the framework, copolymerization patterns will dominate or if self-sorting crystallization will prevail. The former would represent an expeditious route to discover new porous solids. To investigate this question we undertook the synthesis of porous crystals based on two organic linkers of different topologies, namely, terephthalic acid (H2BDC) and 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB). H2BDC is the organic linker that, when combined with Zn, yields MOF-5, a stable cubic structure that is the best studied of the metal–organic frameworks. Using H3BTB under essentially identical synthetic conditions affords MOF177. This trigonal framework exhibits exceptional porosity and surface area and boasts the highest reported uptake of hydrogen gas in a physisorptive material. Combining H2BDC with H3BTB, two ligands possessing aryl carboxylic acid coordinating groups, in the presence of zinc nitrate incorporates both components into a completely new type of structure that can be obtained to the exclusion of materials derived from either pure linker. Figure 1 illustrates the porous crystals produced by heating various ratios of H2BDC and H3BTB in the presence of excess Zn(NO3)2·4H2O at 85 8C for 2 days. Three distinct crystalline phases are observed as the mole fraction of H3BTB is increased. At low H3BTB concentrations, only MOF-5 crystals are formed; however, at a mole ratio of 4:1 (H2BDC:H3BTB), a new needle-shaped phase is formed along with MOF-5. Increasing the H3BTB concentration leads to exclusive formation of the needleshaped phase, which according to powder X-ray diffraction (XRD) data is different from MOF-5 and MOF-177 (Figure S4 in the Supporting Information). A further increase of the H3BTB concentration results in MOF-177 forming as well. Finally, at H2BDC:H3BTB mole ratios greater than or equal to 2:3, MOF-177 is the first product to crystallize out of solution. A single-crystal X-ray diffraction study of the needleshaped crystals revealed a structure with one-dimensional hexagonal channels. The product crystallizes in the space group P63m and dramatically differs from the structures derived from the pure linkers. The framework of the material consists of Zn4O clusters linked together by two BDC and four BTB linkers arranged in an octahedral geometry (Figure 2a). Two BDC linkers are adjacent, leaving the other four positions occupied by BTB linkers, and these octahedra assemble into a structure containing both micropores and mesopores. This product is denoted as UMCM-1 (University of Michigan Crystalline Material-1). The micropores are found in cage-like structures constructed from six BDC linkers, five BTB linkers, and nine Zn4O clusters, and with an internal dimension of approximately 1.4 nm@1.7 nm (subtracting the van der Waals radii of the atoms, Figure 2b). Six such microporous cages assemble together in an edgesharing fashion to define the diameter of the mesopore, a 1D hexagonal channel 2.7 nm@ 3.2 nm (measured between pore walls, Figure 2c). When van der Waals radii of the atoms are taken into account, the mesopore is 2.4 nm@ 2.9 nm. Comparison of the bulk powder XRD pattern to that simulated [*] Dr. K. Koh, Dr. A. G. Wong-Foy, Prof. A. J. Matzger Department of Chemistry and the Macromolecular Science and Engineering Program University of Michigan 930 North University Ave, Ann Arbor, MI 48109-1055 (USA) Fax: (+1)734-6715-8853 E-mail: matzger@umich.edu

The design, synthesis, and properties of the new microporous coordination polymer UMCM-310 are described. The unique electronic character of the perylene-based linker enables selective interaction with electron-poor aromatics leading to efficient separation of nitroaromatics. UMCM-310 possesses high surface area and large pore size and thus permits the separation of large organic molecules based on adsorption rather than size exclusion.

A coordination terpolymerization strategy is introduced to alter the connectivity within layers of a pillared-layer coordination polymer. Assembling two different dicarboxylate linkers around a metal cluster in the layer suppresses interpenetration while enabling formation of a rectangular 2D grid structure.

Moisture can cause irreversible structural collapse in metal-organic frameworks (MOFs) resulting in decreased internal surface areas and pore volumes. The details of such structural collapse with regard to pore size evolution during degradation are currently unknown due to a lack of suitable in situ probes of porosity. Here we acquire MOF porosity data under dynamic conditions by incorporating a flow-through system in tandem with positronium annihilation lifetime spectroscopy (PALS). From the decrease in porosity, we have observed an induction period for water degradation of some Zn4O-based MOFs that signals much greater stability than commonly believed to be possible. The sigmoidal trend in the degradation curve of unfunctionalized MOFs caused by water vapor has been established from the temporal component of pore size evolution as characterized by in situ PALS. IRMOF-3 is found to degrade at a lower relative humidity than MOF-5, a likely consequence of the amine groups in the structure, although, in contrast to MOF-5, residual porosity remains. The presence of an induction period, which itself depends on previous water exposure of the sample (history dependence), and sigmoidal temporal behavior of the moisture-induced degradation mechanism of MOFs was also verified using powder X-ray diffraction analysis and ex situ gas adsorption measurements. Our work provides insight into porosity evolution under application-relevant conditions as well as identifying chemical and structural characteristics influencing stability.

The dicationic complexes [(ArNC(Me)C(Me)NAr)Pt(solv)2]X2, (Ar=2,6-(CH3)2C6H3; 5a: solv=CH3CN, X=CF3SO3−, BF4−, SbF6−; 5b: solv=(CH3)2CO, X=BF4−, SbF6−) and [(CyNC(H)C(H)NCy)Pt(CH3CN)2]X2, (Cy=C6H11, 6: X=OTf−, BF4−, PF6−, SbF6−) were synthesized from the corresponding Pt dichlorides with two equivalents of AgX. The reactions of 5a with 1-phenylpyrazole, 2-phenylpyridine, 2-vinylpyridine, and 2-(2-thienyl)pyridine afford the cyclometalated products 11–14 via intramolecular CH activation of an sp2 CH bond of the unsaturated sidegroup. Pyridines with saturated groups at the 2-position do not undergo a similar cyclometalation reaction. In trifluoroethanol-d3 solution, 6 undergoes cyclometalation of one of the cyclohexyl groups, an example of sp3 CH bond activation. The latter reaction proceeds only partway to completion, implying that an equilibrium has been reached; in the case where X=OTf−the equilibrium favors the starting dication.

Design and synthesis of porous solids employing both reversible coordination chemistry and reversible covalent bond formation is described. The combination of two different linkage modes in a single material presents a link between two distinct classes of porous materials as exemplified by metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). This strategy, in addition to being a compelling material-discovery method, also offers a platform for developing a fundamental understanding of the factors influencing the competing modes of assembly. We also demonstrate that even temporary formation of reversible connections between components may be leveraged to make new phases thus offering design routes to polymorphic frameworks. Moreover, this approach has the striking potential of providing a rich landscape of structurally complex materials from commercially available or readily accessible feedstocks.

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.

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.

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).

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.

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.

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.

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.

The use of a reduced symmetry organic linker for the preparation of porous coordination polymers is demonstrated. The solvothermal reaction of the unsymmetrically substituted biaryl compound biphenyl-3,4‘,5-tricarboxylic acid with Cu(II) ions produces a [3,4,6]-connected coordination polymer exhibiting very high porosity and surface area (SLangmuir = 3100 m2/g). A striking feature of the structure is its incorporation, in a single material, of both the ubiquitous dinuclear Cu(II) paddlewheel motif and the rarely observed trinuclear Cu(II) cluster. Saturation H2 uptake, measured at 77 K, shows an excess gravimetric uptake of 5.7 wt % at 45 bar with a steep rise at low pressures.

Hierarchical chemical structures that incorporate some of the complexity typical of biological assemblies now exist and are being developed for use as highly selective catalysts, sensors, and ion- and drug-transport materials. Generally, such synthetic systems are based on supramolecular structures, for which it is possible to design step-by-step reactions that progressively lead to complex architectures of discrete molecular components. [1] In contrast, the stepwise synthesis of analogous extended (nonmolecular) networks is not feasible, because the intermediates are insoluble. Herein, we present the synthesis of MOF-500, a new metal–organic framework (MOF), to illustrate how a “one-pot” reaction can yield a crystalline solid with four distinct levels of complexity (defined by structural elements of increasing size, with distinct compositions, structures, and pores). Prior knowledge of reaction conditions that yield the porous tetrahedral level-3 building blocks of MOF-500 (Figure 1) obviates the need for a multistep synthesis. [2] We highlight the remarkable similarities between the structure of the extended network MOF-500 and that of its molecular building blocks (IRMOP-51). Furthermore, we demonstrate that a concomitant fourfold increase in gas uptake and surface area occurs on going from the crystals of the molecular building blocks IRMOP-51 to those of the extended network MOF-500. Figure 1 outlines the conceptual and practical aspects of

Saturation H2 uptake in a series of microporous metal−organic frameworks (MOFs) has been measured at 77 K. Saturation pressures vary between 25 and 80 bar across the series, with MOF-177 showing the highest uptake on a gravimetric basis (7.5 wt %) and IRMOF-20 showing the highest uptake on a volumetric basis at 34 g/L. These results demonstrate that maximum H2 storage capacity in MOFs correlates well to surface area, and that feasible volumetric uptakes can be realized even in highly porous materials.

A series of four isostructural microporous coordination polymers (MCPs) differing in metal composition is demonstrated to exhibit exceptional uptake of CO2 at low pressures and ambient temperature. These conditions are particularly relevant for capture of flue gas from coal-fired power plants. A magnesium-based material is presented that is the highest surface area magnesium MCP yet reported and displays ultrahigh affinity based on heat of adsorption for CO2. This study demonstrates that physisorptive materials can achieve affinities and capacities competitive with amine sorbents while greatly reducing the energy cost associated with regeneration.

The utility of microporous coordination polymers (MCPs) for the adsorption of large organosulfur compounds (benzothiophene, dibenzothiophene, 4,6-dimethyldibenzothiophene) found in fuels is demonstrated. Large capacities are obtained at both low and high sulfur concentrations. For 4,6-dimethyldibenzothiophene, the compound most difficult to remove using current industrial techniques, a capacity of 41 g S/kg MCP at 1500 ppmw S is achieved by UMCM-150. It was determined that the size/shape of the pores in the MCP, rather than the surface area or pore volume, is the most important factor controlling adsorption capacity.

The first examples of well-defined, O-donor ligated, late-metal complexes that are competent for alkane C-H activation are reported. These complexes exhibit thermal and protic stability and are efficient catalysts for H/D exchange reactions with alkanes.