There is long-standing interest in developing membranes possessing uniform pores with dimensions in the range of 1 nm and physical continuity in the macroscopic transport direction to meet the needs of challenging small molecule and ionic separations. Here we report facile, scalabe fabrication of polymer membranes with vertically (i.e., along the through-plane direction) aligned 1 nm pores by magnetic-field alignment and subsequent cross-linking of a liquid crystalline mesophase. We utilize a wedge-shaped amphiphilic species as the building block of a thermotropic columnar mesophase with 1 nm ionic nanochannels, and leverage the magnetic anisotropy of the amphiphile to control the alignment of these pores with a magnetic field. In situ X-ray scattering and subsequent optical microscopy reveal the formation of highly ordered nanostructured mesophases and cross-linked polymer films with orientational order parameters of ca. 0.95. High-resolution transmission electron microscopy (TEM) imaging provides direct visualization of long-range persistence of vertically aligned, hexagonally packed nanopores in unprecedented detail, demonstrating high-fidelity retention of structure and alignment after photo-cross-linking. Ionic conductivity measurements on the aligned membranes show a remarkable 85-fold enhancement of conductivity over nonaligned samples. These results provide a path to achieving the large area control of morphology and related enhancement of properties required for high-performance membranes and other applications.

Triply switchable [Co(II)(dpzca)(2)] shows an abrupt, reversible, and hysteretic spin crossover (T(1/2)↓ = 168 K, T(1/2)↑ = 179 K, and ΔT(1/2) = 11 K) between the high-spin (HS) and low-spin (LS) states of cobalt(II), both of which have been structurally characterized. The spin transition is also reversibly triggered by pressure changes. Moreover, in a third reversible switching mechanism for this complex, the magnetic properties can be switched between HS cobalt(II) and LS cobalt(III) by redox.

The recycling or sequestration of carbon dioxide (CO2) from the waste gas of fossil-fuel power plants is widely acknowledged as one of the most realistic strategies for delaying or avoiding the severest environmental, economic, political, and social consequences that will result from global climate change and ocean acidification. For context, in 2013 coal and natural gas power plants accounted for roughly 31% of total U.S. CO2 emissions. Recycling or sequestering this CO2 would reduce U.S. emissions by ca. 1800 million metric tons-easily meeting the U.S.'s currently stated CO2 reduction targets of ca. 17% relative to 2005 levels by 2020. This situation is similar for many developed and developing nations, many of which officially target a 20% reduction relative to 1990 baseline levels by 2020. To make CO2 recycling or sequestration processes technologically and economically viable, the CO2 must first be separated from the rest of the waste gas mixture-which is comprised mostly of nitrogen gas and water (ca. 85%). Of the many potential separation technologies available, membrane technology is particularly attractive due to its low energy operating cost, low maintenance, smaller equipment footprint, and relatively facile retrofit integration with existing power plant designs. From a techno-economic standpoint, the separation of CO2 from flue gas requires membranes that can process extremely high amounts of CO2 over a short time period, a property defined as the membrane "permeance". In contrast, the membrane's CO2/N2 selectivity has only a minor effect on the overall cost of some separation processes once a threshold permeability selectivity of ca. 20 is reached. Given the above criteria, the critical properties when developing membrane materials for postcombustion CO2 separation are CO2 permeability (i.e., the rate of CO2 transport normalized to the material thickness), a reasonable CO2/N2 selectivity (≥20), and the ability to be processed into defect-free thin-films (ca. 100-nm-thick active layer). Traditional polymeric membrane materials are limited by a trade-off between permeability and selectivity empirically described by the "Robeson upper bound"-placing the desired membrane properties beyond reach. Therefore, the investigation of advanced and composite materials that can overcome the limitations of traditional polymeric materials is the focus of significant academic and industrial research. In particular, there has been substantial work on ionic-liquid (IL)-based materials due to their gas transport properties. This review provides an overview of our collaborative work on developing poly(ionic liquid)/ionic liquid (PIL/IL) ion-gel membrane technology. We detail developmental work on the preparation of PIL/IL composites and describe how this chemical technology was adapted to allow the roll-to-roll processing and preparation of membranes with defect-free active layers ca. 100 nm thick, CO2 permeances of over 6000 GPU, and CO2/N2 selectivity of ≥20-properties with the potential to reduce the cost of CO2 remov...

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Membrane separations are critically important in areas ranging from health care and analytical chemistry to bioprocessing and water purification. An ideal nanoporous membrane would consist of a thin film with physically continuous and vertically aligned nanopores and would display a narrow distribution of pore sizes. However, the current state of the art departs considerably from this ideal and is beset by intrinsic trade-offs between permeability and selectivity. We demonstrate an effective and scalable method to fabricate polymer films with ideal membrane morphologies consisting of submicron thickness films with physically continuous and vertically aligned 1 nm pores. The approach is based on soft confinement to control the orientation of a cross-linkable mesophase in which the pores are produced by self-assembly. The scalability, exceptional ease of fabrication, and potential to create a new class of nanofiltration membranes stand out as compelling aspects.

Cluster and periodic density functional theory (DFT) of carbon monoxide adsorbed atop on Pt (COads) show that ruthenium alloying weakens both the COads internal and C−Pt bonds and reduces the COads adsorption energy. A new theoretical model based on the π-attraction σ-repulsion is used to explain the above results. This model correlates (1) Mulliken population, (2) density-of-states analysis of the COads orbitals, (3) the individual interaction of these orbitals with the metal lattice bands, and (4) their polarizations within the COads molecule. In this study, the σ interaction has both attractive and repulsive components via electron donation to the metal bands and Pauli repulsion, respectively. Cluster DFT shows that the overall weakening of the COads internal bond upon alloying is due to the dominance of reduced σ donation to the metal (which weakens the COads internal bond) over increased π bonding between the carbon and oxygen. However, periodic DFT calculations show that both the σ donation and the COads internal π bonding are simultaneously reduced. The C−Pt bond weakening upon alloying is primarily due to increased exchange repulsion between the adsorbate and the substrate. The adsorbing Pt atom sp/d z 2 orbitals population increase upon alloying for both calculations.

C ross-linked room-temperature ionic liquid (RTIL) polymer gels are a new class of functional materials comprised of a liquid RTIL intercalated within a cross-linked polymer matrix. 1−6 RTILs possess many useful properties (e.g., broad liquid range, high ion conductivity, excellent gas diffusivity and selectivity, low vapor pressures), 7,8 but their liquid state is a problem for many applications. Researchers have been able to take advantage of RTILs in a versatile, solid configuration by stabilizing large quantities of RTIL (50−90 wt %) in crosslinked polymer networks. 1−6 The resulting cross-linked polymer/RTIL composites, which have both solid-and liquid-like properties, can be used as functional materials ranging from solid electrolytes to gas separation membranes. 1−6 Several schemes to fabricate physically cross-linked RTIL polymer gels have been investigated using poly(ethylene oxide) or block copolymer systems as the polymer matrix. 5,6 For example, ABA triblock copolymer systems have been developed that physically gel up to 90 wt % RTIL. 2,4 Also, P(VDF-co-HFP) can form gels with ca. 80 wt % RTIL via the crystalline domains in the fluorinated copolymer serving as physical crosslinks. 5,6 There are fewer reports of chemically (i.e., covalently) crosslinked RTIL polymer gels. Several groups have synthesized RTIL polymer gels by radically photopolymerizing mixtures of multifunctional monomers in the presence of a RTIL. 9−11 A related method uses RTIL-based cross-linking monomers to generate gels with a cross-linked poly(RTIL) matrix. These poly(RTIL)/RTIL gel films contain 50−90 wt % RTIL while retaining excellent materials properties. 1,3 However, chemically cross-linked poly(RTIL)/RTIL gels have some disadvantages in terms of thin film processing using conventional casting methods. For example, it is not possible to dissolve the formed RTIL polymer gel because of the covalent cross-links. Furthermore, when casting thin films from soluble monomer/RTIL mixtures (neat or from solution), it is difficult to prevent substantial penetration of these mixtures into porous supportsdue to their low viscosities and low molecular weights (MWs) prior to cross-linking. For high-throughput gas separation applications, it is desirable to cast a thin, defect-free, poly(RTIL)/RTIL gel film atop a porous polymer substrate to form a thin-film composite (TFC) membrane. 12 An alternative to the monomer/RTIL approach is to start with a curable poly(RTIL) rather than a low-MW, crosslinkable monomer. By redesigning the cross-linking component to be an intrinsic part of a fully formed ionic polymer (i.e., a curable poly(RTIL) with polymerizable pendant groups), the resulting reactive polymer/RTIL mixture can be solventprocessed using conventional methods and then cross-linked

New imidazolium- and pyrrolidinium-based bis­(epoxide)-functionalized ionic liquid (IL) monomers were synthesized and reacted with multifunctional amine monomers to produce cross-linked, epoxy–amine poly­(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and chemical nature (i.e., alkyl versus ether) between the imidazolium group and epoxide groups were studied to determine their effects on CO2 affinity. The CO2 uptake (millimoles per gram) of the epoxy–amine resins (between 0.1 and 1 mmol/g) was found to depend predominately on the epoxide-to-amine ratio and the bis­(epoxide) IL molecular weight. The effect of using a primary versus a secondary amine-containing multifunctional monomer was also assessed for the resin synthesis. Secondary amines can increase CO2 permeability but also increase the time required for bis­(epoxide) conversion. When either the epoxide or amine monomer structure is changed, the CO2 solubility and permeability of the resulting PIL resins and ion-gel membranes can be tuned.