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The high temperature performance oforganic field-effect transistorsbased on a molecular organic semiconductor with intermediate dimensions, namely X2, is evaluated. Hole mobility is stable, even at 200-250 °C. Changes in device characteristics at high temperature are reversible across multiple cycles of high temperature operation. Measurements at high temperature exhibit larger hysteresis, while at low temperature one observes the emergence of ambipolar transport.

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.

Random copolymerization is a core strategy of the polymer industry, enabling broad tuning of materials properties through mixing monomers with similar reactivities. In coordination polymers, analogous results have recently been achieved using combinations of isomorphic linkers copolymerized by appropriate metals; in general, the properties of the resultant coordination copolymers can be described as a linear combination of the properties of the constituent building blocks. Here we demonstrate that this need not be the case: coordination copolymerization is a powerful strategy for directing phase formation. For example, reaction of 1,4-benzenedicarboxylic acid with Zn2+ typically affords phase-impure material in N,N-dimethylformamide whereas using an amino functionalized linker leads to pure high surface area material with the structure of MOF-5. However, mixed-linker copolymers derived from a combination of both linkers display surface areas comparable to that of MOF-5 synthesized in N,N-diethylformamide,...

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.

Octaphenylsilsesquioxane (OPS) derivatives represent a class of high functionality building blocks with perfect three-dimensional symmetry for the construction of rigid and highly porous polymers. Copper-mediated in-situ homocoupling of an OPS derivative with eight para-disposed triple bonds yields a porous network with surface areas up to 1000 m2/g. Introducing a monoalkyne capping agent to lower cross-linking density led to a ∼200 m2/g increase in surface area. Exceptional thermal robustness of the silsesquioxane cage and strong covalent bonds resulting from the cross-linking process render the resulting porous networks stable to heat and water.

A predictive tool termed the linker to metal cluster (LiMe) ratio is introduced as a method for understanding surface area in microporous coordination polymers (MCPs). Calibrated with geometric accessible surface area computations, the LiMe ratio uses molecular weight of building block components to indicate the maximum attainable surface area for a given linker and metal cluster combination. MOF-5 and HKUST-1 are used as prototypical structures to analyze MCPs with octahedral M(4)O(CO(2)R)(6) and paddlewheel M(2)(CO(2)R)(4) metal clusters. Insight into the effects of linker size, geometry, number of coordinating groups, and framework interpenetration is revealed through the LiMe ratio analysis of various MCPs. Experimental surface area deviation provides indication that a material may suffer from incomplete guest removal, structural collapse, or interpenetration. Because minimal data input are required, the LiMe ratio surface area analysis is suggested as a quick method for experimental verification as well as a guide for the design of new materials.

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

Incompletely condensed, fluorinated polyhedral oligomeric silsesquioxane with the highly reactive group of trisodium silanolate was used for the synthesis of an initiator for atom transfer radical polymerization. The initiator was applied to solution polymerization of methyl methacrylate (MMA) in the presence of a copper complex. The polymerization proceeded in a living fashion, providing tadpole-shaped polymers with an “inorganic head” of polyhedral oligomeric silsesquioxane (POSS) and an “organic tail” of well-defined PMMA. A blend film composed of the tadpole-shaped polymer and a matrix PMMA was annealed at 180 °C for 5 days and then analyzed by neutron reflectometry, X-ray photoelectron spectroscopy, and contact angle measurement. These analyses revealed that the tadpole-shaped polymer was preferentially populated at the air/polymer interface, and the outermost layer of the film was almost completely covered by the POSS heads. This was mainly due to the low surface free energy of the fluorinated POSS ...

Monodisperse silica particles (SiPs) of diameter between 100 and 1500 nm were surface-modified in a mixture of ethanol/water/ammonia with a newly designed triethoxysilane having an atom transfer radical polymerization (ATRP) initiating site, (2-bromo-2-methyl)propionyloxyhexyltriethoxysilane. The surface-initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator-fixed SiPs in the presence of a “sacrificial” (free) initiator. The polymerization proceeded in a living manner in all examined cases, producing SiPs coated with well-defined PMMA of a target molecular weight up to 480K with a graft density as high as 0.65 chains/nm2. These hybrid particles had an exceptionally good dispersibility in organic solvents. Transmission electron microscopic and atomic force microscopic observations of their monolayers prepared at the air−water interface revealed that they formed an ordered 2-dimensional lattice extending throughout the monolayer.

Incompletely condensed polyhedral oligomeric silsesquioxane (POSS) with the highly reactive group of trisodium silanolate was used for the synthesis of two initiators for atom transfer radical polymerization, one with a 2-bromoisobutyl group and the other with a chlorosulfonyl group. These initiators were applied to solution polymerizations of styrene and methyl methacrylate in the presence of a copper complex. In both systems, polymerization proceeded in a living fashion, as indicated by the first-order kinetics of monomer consumption, the evolution of molecular weight in direct proportion to monomer conversion, the good agreement of molecular weight with the theoretical one, and the low polydispersity, thus providing tadpole-shaped polymers with an “inorganic head” of POSS and an “organic tail” of well-defined polymer. Thermogravimetric and differential scanning calorimetric studies showed that both thermal degradation and glass transition temperatures of the organic/inorganic hybrid polymers with molec...

Copper-mediated atom transfer radical polymerization (ATRP) of a protected silanol group-holding methacrylate, methacryloxypropyltrimethoxysilane (MOPS), was investigated. In a dry condition using carefully distilled solvent and monomer, the polymerization proceeded in a living fashion providing a low-polydispersity polymer with a predicted molecular weight. The ATRP in conjunction with the sequential monomer addition of methyl methacrylate (MMA) and MOPS afforded a block copolymer of the type PMMA-b-poly(MMA-r-MOPS). The heat treatment of a solution of the block copolymer in the presence of a catalytic amount of ammonia gave a polymeric core-shell nanoparticle with a shell of PMMA moieties and a core of the poly(MMA-r-MOPS) blocks cross-linked via the condensation of the trimethoxysilane groups of the MOPS moieties.

The synthesis of a gold nanoparticle (AuNP) coated with a well-defined polymer is reported. The AuNP coated with an initiator group for living radical polymerization was prepared by the simple one-pot reduction of tetrachloroaurate with sodium borohydrate in the presence of an initiator group-holding disulfide. The surface-initiated living radical polymerization of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator-coated AuNP in the presence of a “sacrificial” free initiator. Living polymerization proceeded exhibiting a first-order kinetics of monomer consumption and an evolution of molecular weight of the graft polymer proportional to monomer conversion, thus providing well-defined, low-polydispersity graft polymers with an approximate graft density of 0.3 chains/nm2. Transmission electron microscopic observations of as-cast films of the AuNPs coated with PMMAs (PMMA−AuNPs) revealed that the particles were well dispersed in the polymer matrix without forming aggreg...

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.

The diffusion of individual Nile red molecules in three different crystalline microporous coordination polymers (MCPs) is visualized with single-molecule fluorescence microscopy. By localizing molecules with high spatial resolution, the trajectories of the diffusing dyes are reconstructed with nanometer-scale precision. A detailed analysis of these tracks reveals different dynamics and guest-host interactions in each crystal as well as distinct motion types within the same system, suggesting the presence of structural heterogeneities in local environments.

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.

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.

Chemical patterning of inorganic substrates by soft lithography has enabled various high-tech applications and cutting-edge fundamental research. In this paper, we report on methods for the grafting and patterned grafting of block copolymer nanotubes onto glass and mica surfaces. Under optimized conditions the density of such grafted nanotubes can be high, and most of the grafted tubes are in a standing position even after solvent evaporation. Surfaces modified with exotic reagents such as block copolymer nanofibers or nanotubes may find applications in biosensing, etc.

A diverse collection of 14 metal-organic frameworks (MOFs) was screened for CO(2) capture from flue gas using a combined experimental and modeling approach. Adsorption measurements are reported for the screened MOFs at room temperature up to 1 bar. These data are used to validate a generalized strategy for molecular modeling of CO(2) and other small molecules in MOFs. MOFs possessing a high density of open metal sites are found to adsorb significant amounts of CO(2) even at low pressure. An excellent correlation is found between the heat of adsorption and the amount of CO(2) adsorbed below 1 bar. Molecular modeling can aid in selection of adsorbents for CO(2) capture from flue gas by screening a large number of MOFs.

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.