The air-free reaction between FeCl 2 and H 4 dobdc (dobdc 4À = 2,5-dioxido-1,4-benzenedicarboxylate) in a mixture of N,N-dimethylformamide (DMF) and methanol affords Fe 2 (dobdc) 3 4DMF, a metalÀorganic framework adopting the MOF-74 (or CPO-27) structure type. The desolvated form of this material displays a BrunauerÀEmmettÀTeller (BET) surface area of 1360 m 2 /g and features a hexagonal array of onedimensional channels lined with coordinatively unsaturated Fe II centers. Gas adsorption isotherms at 298 K indicate that Fe 2 (dobdc) binds O 2 preferentially over N 2 , with an irreversible capacity of 9.3 wt %, corresponding to the adsorption of one O 2 molecule per two iron centers. Remarkably, at 211 K, O 2 uptake is fully reversible and the capacity increases to 18.2 wt %, corresponding to the adsorption of one O 2 molecule per iron center. M€ ossbauer and infrared spectra are consistent with partial charge transfer from iron(II) to O 2 at low temperature and complete charge transfer to form iron(III) and O 2 2À at room temperature. The results of Rietveld analyses of powder neutron diffraction data (4 K) confirm this interpretation, revealing O 2 bound to iron in a symmetric sideon mode with d OÀO = 1.25(1) Å at low temperature and in a slipped side-on mode with d OÀO = 1.6(1) Å when oxidized at room temperature. Application of ideal adsorbed solution theory in simulating breakthrough curves shows Fe 2 (dobdc) to be a promising material for the separation of O 2 from air at temperatures well above those currently employed in industrial settings. ' INTRODUCTIONWith over 100 million tons produced annually, O 2 is one of the most widely used commodity chemicals in the world. 1 Its potential utility in processes associated with the reduction of carbon dioxide emissions from fossil fuel-burning power plants, however, means that the demand for pure O 2 could grow enormously. For implementation of precombustion CO 2 capture, pure O 2 is needed for the gasification of coal, which produces the feedstock for the waterÀgas shift reaction used to produce CO 2 and H 2 . 2 In addition, oxyfuel combustion is receiving considerable attention for its potential utility as an alternative to postcombustion CO 2 capture. Here, pure O 2 is diluted to 0.21 bar with CO 2 and fed into a power plant for fuel combustion. Since N 2 is absent from the resulting flue gas, the requirement for postcombustion separation of CO 2 from N 2 is eliminated. 3 The separation of O 2 from air is currently carried out on a large scale using an energy-intensive cryogenic distillation process. 4 Zeolites are also used for O 2 /N 2 separation, 5 both industrially and in portable medical devices; however, this process is inherently inefficient as the materials used adsorb N 2 over O 2 with poor selectivity. By employing materials that selectively adsorb

Comprehensive study of carbon dioxide adsorption in the metal-organic frameworks M 2 (dobdc) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn)The results reveal important, molecular level detail of CO 2 binding in a prominent family of Metal-Organic Frameworks whose adsorption properties can be readily tuned with metal-substitution. This information, which is of signifi cant importance in the context of carbon capture, allows us to make a detailed comparison with DFT calculations; theoretical results show excellent agreement with experimental determination of intramolecular CO 2 angles, CO 2 binding geometries, and isosteric heats of CO 2 adsorption.

Rietveld analyses of neutron powder diffraction data of D2 in Cu3(BTC)2, where BTC = 1,3,5-benzenetricarboxylate, reveals the location and progressive filling of six distinct D2 sites within the nanopore structure. Location of the primary site at the coordinatively unsaturated Cu atoms provides direct structural evidence of the potential importance of such metal sites to hydrogen storage. Competitive loading of the other D2 sites proceeds with the pores filling from smallest to largest.

Multi-temperature X-ray diffraction studies show that twisting, rotation, and libration cause negative thermal expansion (NTE) of the nanoporous metal−organic framework MOF-5, Zn4O(1,4-benzenedicarboxylate)3. The near-linear lattice contraction is quantified in the temperature range 80−500 K using synchrotron powder X-ray diffraction. Vibrational motions causing the abnormal expansion behavior are evidenced by shortening of certain interatomic distances with increasing temperature according to single-crystal X-ray diffraction on a guest-free crystal over a broad temperature range. Detailed analysis of the atomic positional and displacement parameters suggests two contributions to cause the effect: (1) local twisting and vibrational motion of the carboxylate groups and (2) concerted transverse vibration of the linear linkers. The vibrational mechanism is confirmed by calculations of the dynamics in a molecular fragment of the framework.

Owing to their high conductivity, crystalline Li 7-3x Ga x La 3 Zr 2 O 12 garnets are promising electrolytes for allsolid-state lithium-ion batteries. Herein, the influence of Ga doping on the phase, lithium-ion distribution, and conductivity of Li 7-3x Ga x La 3 Zr 2 O 12 garnets is investigated, with the determined concentration and mobility of lithium ions shedding light on the origin of the high conductivity of Li 7-3x Ga x La 3 Zr 2 O 12 . When the Ga concentration exceeds 0.20 Ga per formula unit, the garnet-type material is found to assume a cubic structure, but lower Ga concentrations result in the coexistence of cubic and tetragonal phases. Most lithium within Li 7-3x Ga x La 3 Zr 2 O 12 is found to reside at the octahedral 96h site, away from the central octahedral 48g site, while the remaining lithium resides at the tetrahedral 24d site. Such kind of lithium distribution leads to high lithium-ion mobility, which is the origin of the high conductivity; the highest lithium-ion conductivity of 1.46 mS/cm at 25 °C is found to be achieved for Li 7-3x Ga x La 3 Zr 2 O 12 at x = 0.25. Additionally, there are two lithium-ion migration pathways in the Li 7-3x Ga x La 3 Zr 2 O 12 garnets: 96h-96h and 24d-96h-24d, but the lithium ions transporting through the 96h-96h pathway determine the overall conductivity. Disciplines Engineering | Physical Sciences and Mathematics

All-solid-state rechargeable lithium-ion batteries (AS-LIBs) are attractive power sources for electrochemical applications due to their potentiality in improving safety and stability over conventional batteries with liquid electrolytes. Finding a solid electrolyte with high ionic conductivity and compatibility with other battery components is a key factor in raising the performance of AS-LIBs. In this work, we prepare argyrodite-type Li 6 PS 5 X (X = Cl, Br, I) using mechanical milling followed by annealing. X-ray diffraction characterization reveals the formation and growth of crystalline Li 6 PS 5 X in all cases. Ionic conductivity of the order of 7×10 −4 S cm −1 in Li 6 PS 5 Cl and Li 6 PS 5 Br renders these phases suitable for AS-LIBs. Joint structure refinements using high-resolution neutron and laboratory X-ray diffraction provide insight into the influence of disorder on the fast ionic conductivity. Besides the disorder in the lithium distribution, it is the disorder in the S 2− /Cl − or S 2− /Br − distribution that we find to promote ion mobility, whereas the large I − cannot be exchanged for S 2− and the resulting more ordered Li 6 PS 5 I exhibits only a moderate conductivity. Li + ion migration pathways in the crystalline compounds are modelled using the bond valence approach to interpret the differences between argyrodites containing different halide ions.

In recent years the phenomenon of negative thermal expansion (NTE; that is, contraction upon warming) over a broad temperature range has been detected in a select group of materials [1] and attributed to mechanisms that include electronic and magnetic transitions [2] and transverse atomic and molecular vibrations. [1,[3][4][5][6][7][8] Among the vibrational systems, materials that have received particular attention include AM 2 O 8 , AM 2 O 7 , A 2 M 3 O 12 , and a number of zeolites, [3] which contain MÀOÀM' bridges that undergo transverse vibration to cause contraction of the M-M' distance, and a diverse family of metal cyanides, [4][5][6][7][8] which contain MÀCNÀM' bridges that show an analogous effect but with increased vibrational flexibility. The presence of a highly flexible diatomic linker in the cyanide phases leads to pronounced thermal expansion behavior, examples of which include the largest isotropic [4] and anisotropic [5] NTE reported to date. A common NTE mechanism proposed for both the oxide and cyanide systems is the coupling of these transverse vibrations into concerted low-energy lattice modes that involve the rotation and/or translation of undistorted metal-coordination polyhedra, known as rigid unit modes (RUMs).[9] With thermal population, these modes counteract the higherenergy longitudinal modes that cause bond-length expansion, thereby leading to bulk NTE behavior.Recently, NTE has also been proposed in a series of isoreticular metal-organic framework (IRMOF) materials following the detected thermal contraction of gas-sorbed samples of IRMOF-1.[10] Theoretical simulations [11] of these materials have suggested an NTE mechanism closely analogous to that of the metal cyanide phases, [6,7] involving the transverse vibration of linear organic linkers. Following a more general investigation of such materials, herein we present the NTE properties of [Cu 3 (btc) 2 ] (btc = 1,3,5-benzenetricarboxylate), a metal-organic framework that consists of dicopper tetracarboxylate "paddlewheels" and aromatic ring motifs.[12] Through crystallographic characterization we elucidate a structural mechanism that involves two unique components: transverse vibration of planar, rather than linear, linkers, and local molecular vibrations within the framework.The highly symmetric structure of [Cu 3 (btc) 2 ] can be conveniently considered as consisting of octahedral supramolecular cages that link through their vertices to form a three-dimensional cubic framework (Figure 1 inset). As the material readily binds atmospheric water and gases at the coordinatively unsaturated Cu sites, [13] samples for powder and single-crystal X-ray diffraction measurement were sealed under vacuum in glass capillaries following their thorough

Because of its stability, nanosized olivine LiFePO(4) opens the door toward high-power Li-ion battery technology for large-scale applications as required for plug-in hybrid vehicles. Here, we reveal that the thermodynamics of first-order phase transitions in nanoinsertion materials is distinctly different from bulk materials as demonstrated by the decreasing miscibility gap that appears to be strongly dependent on the overall composition in LiFePO(4). In contrast to our common thermodynamic knowledge, that dictates solubility limits to be independent of the overall composition, combined neutron and X-ray diffraction reveals strongly varying solubility limits below particle sizes of 35 nm. A rationale is found based on modeling of the diffuse interface. Size confinement of the lithium concentration gradient, which exists at the phase boundary, competes with the in bulk energetically favorable compositions. Consequently, temperature and size diagrams of nanomaterials require complete reconsideration, being strongly dependent on the overall composition. This is vital knowledge for the future nanoarchitecturing of superior energy storage devices as the performance will heavily depend on the disclosed nanoionic properties.