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Aminophosphines are a class of inexpensive, environmentally benign phosphorus precursors that have provided routes to various metal phosphides. In this work, we use the aminophosphine tris(diethyl)aminophosphine to synthesize tin phosphide nanocrystals.

Understanding mechanisms of decontamination of chemical warfare agents (CWA) is an area of intense research aimed at developing new filtration materials to protect soldiers and civilians in case of state-sponsored or terrorist attack. In this study, we employed complementary structural, chemical, and dynamic probes and in situ data collection, to elucidate the complex chemistry, capture, and decomposition of the CWA simulant, dimethyl chlorophosphonate (DMCP). Our work reveals key details of the reactive adsorption of DMCP and demonstrates the versatility of zeolitic imidazolate framework (ZIF-8) as a plausible material for CWA capture and decomposition. The in situ synchrotron-based powder X-ray diffraction (PXRD) and pair distribution function (PDF) studies, combined with Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), zinc K-edge X-ray absorption near edge structure (XANES), and Raman spectroscopies, showed that the unique structure, chemical state, and topology of ZIF-8 enable accessibility, adsorption, and hydrolysis of DMCP into the pores and revealed the importance of linker chemistry and Zn2+ sites for nerve agent decomposition. DMCP decontamination and decomposition product(s) formation were observed by thermogravimetric analysis, FT-IR spectroscopy, and phosphorus (P) K-edge XANES studies. Differential PDF analysis indicated that the average structure of ZIF-8 (at the 30 A scale) remains unchanged after DMCP dosing and provided information on the dynamics of interactions of DMCP with the ZIF-8 framework. Using in situ PXRD and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), we showed that nearly 90% regeneration of the ZIF-8 structure and complete liberation of DMCP and decomposition products occur upon heating.

The Defense Synchrotron Consortium (DSC) at Brookhaven National Laboratory, to be established in early 2020, has emerged from concerted efforts by the Defense Threat Reduction Agency (DTRA) of the ...

Developing novel and more efficient filters for chemical warfare agent (CWA) decomposition remains an important challenge for modern technology due to the continuous threat those weapons present in...

Diopside ($$CaMgSi_{2}O_{6}$$), the Ca- and Mg-rich clinopyroxene is an important mineral in the Earth’s upper mantle and subducted lithospheric plate. Here, we report the results of high-pressure single-crystal X-ray diffraction experiments conducted on a natural aluminous iron-bearing diopside and a natural, nearly end-member diopside, up to 50 GPa in diamond anvil cell. Density functional theory calculation results on end-member diopside are also reported. Unit cell parameters a, b, c, $$\beta$$, V, as well as bond lengths of diopside are reported and compared with other clinopyroxenes. Bulk modulus and its pressure derivative of the two diopside samples are determined using third-order Birch–Murnaghan equation of state. The density of the two diopside samples is calculated under cold subducting slab conditions and is compared with the seismic models. Along the cold slab geotherm, aluminous iron-bearing diopside has higher density than end-member diopside. In the upper mantle, eclogite with aluminous iron-bearing diopside is denser than eclogite with end-member diopside, and, therefore, provides larger slab pulling force. At the bottom of the transition zone and the top of the lower mantle, eclogite with aluminous iron-bearing diopside, though higher in density than the end-member diopside, is still less dense than the surrounding mantle and could contribute to the slab stagnation.

A commercially available combined X-ray diffraction – differential scanning calorimetry (XRD-DSC) stage was adapted for studies of gas loading in microporous materials, including metal organic frameworks (MOFs). Insertion of a custom-built humid atmosphere swing chamber (HASC) between a humidity generator and the XRD-DSC stage facilitates both humid atmosphere and vacuum swing gas loading. The HASC is necessary to buffer between the humidity generator and the XRD-DSC stage, allowing the gas mixture to homogenize prior to sample exposure, so that both humid atmosphere and vacuum swings could be performed. The changes in XRD can be used to follow structural changes, including collapse, which is indicative of a lack of microporosity upon activation, and the flexibity of frameworks upon gas sorption–desorption cycles. Measurements of the area under the DSC curve allows for calculation of the isosteric heat of adsorption (Qst; kJ molGAS−1). Vacuum-atmosphere swing experiments performed at different pressure steps allow for the reconstruction of the enthalpy of gas adsorption before and after a phase transition. These modes of operation are illustrated in three case studies from a program of exploratory MOF synthesis used to discover novel materials for selective gas sorption from humid gas streams: (1) gas binding in Stony Brook metal organic framework-1, (2) zeolitic imidazolate framework-7 response to variable pressure vacuum-atmosphere swing, and (3) high throughput evaluation of the selectivity of novel MOFs synthesized from customized linkers.

The Zr-containing polyoxometalates (POMs), including (Et2NH2)8{[α-PW11O39Zr(μ–OH)(H2O)]2}·7H2O (1), effectively catalyze the hydrolysis of nerve agent simulants at near-neutral pH. Analogous Zr-containing heterogeneous systems are much-studied and effective nerve-agent hydrolysis catalysts, but due to their heterogeneous nature, it is very challenging to know the exact structure of the catalytic sites during turnover and to clarify at the molecular level the elementary mechanistic processes. Here, under homogeneous conditions, hydrolysis rates of the nerve-agent simulant methyl paraoxon catalyzed by 1 are examined as a function of pH, ionic strength, catalyst, and substrate concentrations. In addition, the specific effect of three commonly used buffers is examined, revealing that acetate functions as a co-catalyst, phosphate inhibits hydrolytic activity, and 2-(N-morpholino)ethanesulfonic acid (MES) has no effect on the hydrolysis rate. Spectroscopic (31P nuclear magnetic resonance) and computational stud...

The mechanism and kinetics of interactions between dimethyl methylphosphonate (DMMP), a key chemical warfare agent (CWA) simulant, and Zr6-based metal organic frameworks (MOFs) have been investigated with in situ infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), and DFT calculations. DMMP was found to adsorb molecularly to UiO-66 through the formation of hydrogen bonds between the phosphoryl oxygen and the free hydroxyl groups associated with Zr6 nodes on the surface of crystallites and not within the bulk MOF structure. Unlike UiO-66, the infrared spectra for UiO-67 and MOF-808, recorded during DMMP exposure, suggest that uptake occurs through both physisorption and chemisorption. The XPS spectra of MOF-808 zirconium 3d electrons reveal a charge redistribution following exposure to DMMP. In addition, analysis of the phosphorus 2p electrons following exposure and thermal annealing to 600 K indicates that two types of stable phosphorus-containing species e...

Hydrocarbon diffusion and binding within porous molecular networks are critical to catalysis, separations, and purification technologies. Fundamental insight into n-butane uptake and mobility within a new class of materials for separations, metal–organic frameworks (MOFs), has been gained through in situ infrared spectroscopy. These ultrahigh vacuum (UHV) based measurements revealed that adsorption of n-butane within UiO-66 proceeds through the formation of hydrogen bonds between the alkane molecules and hydroxyl groups located at the inorganic node of UiO-66. Modeling the gas transport of n-butane with Fick’s second law yielded diffusion coefficients at several temperatures. The Arrhenius parameter for the activation energy of diffusion was found to be 21.0 ± 1.2 kJ/mol. These studies have further shown that the rate-determining step for diffusion is likely the dissociation of n-butane from a binding site located within the tetrahedral pores of UiO-66.

The threat of chemical warfare agents (CWAs), assured by their ease of synthesis and effectiveness as a terrorizing weapon, will persist long after the once-tremendous stockpiles in the U.S. and elsewhere are finally destroyed. As such, soldier and civilian protection, battlefield decontamination, and environmental remediation from CWAs remain top national security priorities. New chemical approaches for the fast and complete destruction of CWAs have been an active field of research for many decades, and new technologies have generated immense interest. In particular, our research team and others have shown metal-organic frameworks (MOFs) and polyoxometalates (POMs) to be active for sequestering CWAs and even catalyzing the rapid hydrolysis of agents. In this Forum Article, we highlight recent advancements made in the understanding and evaluation of POMs and Zr-based MOFs as CWA decontamination materials. Specifically, our aim is to bridge the gap between controlled, solution-phase laboratory studies and real-world or battlefield-like conditions by examining agent-material interactions at the gas-solid interface utilizing a multimodal experimental and computational approach. Herein, we report our progress in addressing the following research goals: (1) elucidating molecular-level mechanisms of the adsorption, diffusion, and reaction of CWA and CWA simulants within a series of Zr-based MOFs, such as UiO-66, MOF-808, and NU-1000, and POMs, including Cs8Nb6O19 and (Et2NH2)8[(α-PW11O39Zr(μ-OH)(H2O))2]·7H2O, (2) probing the effects that common ambient gases, such as CO2, SO2, and NO2, have on the efficacy of the MOF and POM materials for CWA destruction, and (3) using CWA simulant results to develop hypotheses for live agent chemistry. Key hypotheses are then tested with targeted live agent studies. Overall, our collaborative effort has provided insight into the fundamental aspects of agent-material interactions and revealed strategies for new catalyst development.

Zr-based metal organic frameworks (MOFs) have been recently shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. We report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination of DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. These experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontaminat...

Metal–semiconductor hybrid nanoparticles (NPs) offer interesting synergistic properties, leading to unique behaviors that have already been exploited in photocatalysis, electrical, and optoelectronic applications. A fundamental aspect in the synthesis of metal–semiconductor hybrid NPs is the possible diffusion of the metal species through the semiconductor lattice. The importance of understanding and controlling the co-diffusion of different constituents is demonstrated in the synthesis of various hollow-structured NPs via the Kirkendall effect. Here, we used a postsynthesis room-temperature reaction between AuCl3 and InAs nanocrystals (NCs) to form metal–semiconductor core–shell hybrid NPs through the “reversed Kirkendall effect”. In the presented system, the diffusion rate of the inward diffusing species (Au) is faster than that of the outward diffusing species (InAs), which results in the formation of a crystalline metallic Au core surrounded by an amorphous, oxidized InAs shell containing nanoscale vo...

Gate-opening is a unique and interesting phenomenon commonly observed in flexible porous frameworks, where the pore characteristics and/or crystal structures change in response to external stimuli such as adding or removing guest molecules. For gate-opening that is induced by gas adsorption, the pore-opening pressure often varies for different adsorbate molecules and, thus, can be applied to selectively separate a gas mixture. The detailed understanding of this phenomenon is of fundamental importance to the design of industrially applicable gas-selective sorbents, which remains under investigated due to the lack of direct structural evidence for such systems. We report a mechanistic study of gas-induced gate-opening process of a microporous metal-organic framework, [Mn(ina)2 ] (ina=isonicotinate) associated with commensurate adsorption, by a combination of several analytical techniques including single crystal X-ray diffraction, in situ powder X-ray diffraction coupled with differential scanning calorimetry (XRD-DSC), and gas adsorption-desorption methods. Our study reveals that the pronounced and reversible gate opening/closing phenomena observed in [Mn(ina)2 ] are coupled with a structural transition that involves rotation of the organic linker molecules as a result of interaction of the framework with adsorbed gas molecules including carbon dioxide and propane. The onset pressure to open the gate correlates with the extent of such interaction.

The adsorption mechanism of ethane, ethylene, and acetylene (C2Hn; n = 2, 4, 6) on two microporous metal organic frameworks (MOFs) is described here that is consistent with observations from single crystal and powder X-ray diffraction, calorimetric measurements, and gas adsorption isotherm measurements. Two calcium-based MOFs, designated as SBMOF-1 and SBMOF-2 (SB: Stony Brook), form three-dimensional frameworks with one-dimensional open channels. As determined from single crystal diffraction experiments, channel geometries of both SBMOF-1 and SBMOF-2 provide multiple adsorption sites for hydrocarbon molecules through C–H···π and C–H···O interactions, similarly to interactions in the molecular and protein crystals. Both materials selectively adsorb C2 hydrocarbon gases over methane as determined with IAST and breakthrough calculations as well as experimental breakthrough measurements, with C2H6/CH4 selectivity as high as 74 in SBMOF-1.

The efficiency of physisorption-based separation of gas-mixtures depends on the selectivity of adsorbent which is directly linked to size, shape, polarizability and other physical properties of adsorbed molecules. Commensurate adsorption is an interesting and important adsorption phenomenon, where the adsorbed amount, location, and orientation of an adsorbate are commensurate with the crystal symmetry of the adsorbent. Understanding this phenomenon is important and beneficial as it can provide vital information about adsorbate–adsorbent interaction and adsorption–desorption mechanism. So far, only sporadic examples of commensurate adsorption have been reported in porous materials such as zeolites and metal organic frameworks (MOFs). In this work we show for the first time direct structural evidence of commensurate-to-incommensurate transition of linear hydrocarbon molecules (C2–C7) in a microporous MOF, by employing a number of analytical techniques including single crystal X-ray diffraction (SCXRD), in situ powder X-ray diffraction coupled with differential scanning calorimetry (PXRD-DSC), gas adsorption and molecular simulations.

Combined application of in situ X-ray diffraction (XRD) and differential scanning calorimetry (DSC) is a novel technique for rapidly evaluating the suitability of microporous materials for postcombustion CO2 capture. Further, while many microporous materials show promise for CO2 capture, most are not evaluated in the presence of water vapor, a major component of postcombustion flue gas. As a demonstration of the versatility of XRD-DSC techniques, representatives of the classes of materials typically proposed for CO2 capture, zeolites, and metal–organic frameworks (MOFs) were studied: zeolite NaX, Ni-MOF-74 [Ni2(dobdc); dobdc = 2,5-dihydroxyterephthalate], ZIF-7 [ZIF: zeolitic imidazole framework, Zn(phim)2; phim: benzimidazole], and SBMOF-1 [Ca(sdb); sdb: 4,4′-sulfonyldibenzoate]. Although NaX and Ni-MOF-74 show very high affinity toward CO2 under idealized dry conditions, they are also very sensitive to the presence of water vapor and experience significant performance loss above 25% relative humidity (R...

Modeling fluid flow dynamics in metal organic frameworks (MOFs) is a required step toward understanding mechanisms of their activity as novel catalysts, sensors, and filtration materials. We adapted a lattice Boltzmann model, previously used for studying flow dynamics in meso- and microporous media, to the nanoscale dimensions of the MOF pores. Using this model, rapid screening of permeability of a large number of MOF structures, in different crystallographic directions, is possible. The method was illustrated here on the example of an anisotropic MOF, for which we calculated permeability values in different flow directions. This method can be generalized to a large class of MOFs and used to design MOFs with the desired gas flow permeabilities.

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of 85Kr and 129I2 due to their volatility and long half-life. Efficient capture of 129I2 ( t1/2 = 15.7 × 106 years) from the nuclear waste stream can help reduce the risk of releasing I2 radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I2 adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I2 in the presence of water vapor are thus of great interest. Herein, we report on the I2 adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I2 within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine.

We have determined the mid-IR optical constants of one alkali feldspar and four pyroxene compositions in the range of 250–4000 cm−1. Measured reflectance spectra of oriented single crystals were iteratively fit to modeled spectra derived from classical dispersion analysis. We present the real and imaginary indices of refraction ( n and k ) along with the oscillator parameters with which they were modeled. While materials of orthorhombic symmetry and higher are well covered by the current literature, optical constants have been derived for only a handful of geologically relevant monoclinic materials, including gypsum and orthoclase. Two input parameters that go into radiative transfer models, the scattering phase function and the single scattering albedo, are functions of a material’s optical constants. Pyroxene is a common rock-forming mineral group in terrestrial bodies as well as meteorites and is also detected in cosmic dust. Hence, having a set of pyroxene optical constants will provide additional details about the composition of Solar System bodies and circumstellar materials. We follow the method of Mayerhofer et al. (2010), which is based on the Berreman 4 × 4 matrix formulation. This approach provides a consistent way to calculate the reflectance coefficients in low-symmetry cases. Additionally, while many models assume normal incidence to simplify the dispersion relations, this more general model applies to reflectance spectra collected at non-normal incidence.

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu2S) NCs through a redox reaction with iodine molecules (I2), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu2S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sized NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.

A three dimensional lithium hydronium sulfate LiSO4·H3O [1], [space group Pna21 a=8.7785(12) A, b=9.1297(12) A, c=5.2799(7) A, V=423.16(10) A3] was synthesized via solvothermal methods using 1,5-naphthalenedisulfonic acid (1,5-NSA) as the source of sulfate ions. The structure of [1], determined by single crystal X-ray diffraction techniques, consists of corner sharing LiO4 and SO4 tetrahedra, forming an anionic 3-D open framework that is charge balanced by hydronium ions positioned within channels running along [001] and forming strong H-bonding with the framework oxygen atoms. Compound [1] undergoes two reversible phase transitions, involving reorientation of SO42− ions at pressures of approximately 2.5 and 5 GPa at room temperature, as evident from characteristic discontinuous frequency drops in the ν1 mode of the Raman spectra. Additionally, compound [1] forms dense β-lithium sulfate at 300 °C, as evident from temperature dependent powder XRD and combined reversible TGA-DSC experiments.

A series of three magnesium trimesate coordination networks was synthesized from identical reaction mixtures by varying synthetic temperature. Mg(HBTC)(DMF)2·[(CH3)2NH] (1; BTC = trimesate; space group P63/m, a = 16.596(4) A, c = 14.351(8) A) crystallizes at 65 °C, Mg3(BTC)(HCOO)3(DMF)3 (2; space group P ¯ 3, a = 13.928(2) A, c = 8.025(6) A) crystallizes at 100 °C, and Mg3(BTC)2(DMF)4 (3; space group P21/c, a = 17.490(4) A, b = 11.940(2) A, c = 18.460(4) A, β = 116.87(3)°) crystallizes at a temperature of 180 °C. Each network contains metal-coordinated solvent DMF molecules, but thermodynamics and solvent hydrolysis play major roles in structure formation. Compounds 1 and 2 are two-dimensional networks which incorporate hydrolysis byproducts. Compound 3 is a three-dimensional network and shows no inclusion of byproducts. The series follows the trend of increased network connectivity resulting from increased temperature. Each of the networks show a weak photoluminescence response, suggesting that coordinated solvent molecules and interlayer species play a role in quenching photoluminescence.

Three topologically-related lanthanide thiophenedicarboxylate (TDC) metal-organic frameworks were synthesized using an identical metal:linker:solvet ratio. Nd(TDC)3(EtOH)3(H2O)·H2O (1; space group Cc, a = 24.035(2) A, b = 10.063(1) A, c = 18.998(1) A, β = 132.41(1)°) contains the same metal-TDC coordination modes as two other compounds which have the isostructural formula Ln(TDC)3(EtOH)3(H2O)·H2O; Ln = Tb (2; space group P ¯ 1, a = 12.807(9) A, b = 14.557(1) A, c = 19.128(1) A, α = 106.66(2)°, β = 105.62(2)°, γ = 93.691(2)°), Dy (3; space group P ¯ 1, a = 12.793(8) A, b = 14.682(1) A, c = 19.077(1) A, α = 107.12(1)°, β = 105.54(1)°, γ = 93.518(2)°). An equimolar solvent mixture of water and ethanol causes both types of solvent molecules coordinating to metal centers. The fluorescence spectra of compounds 2 and 3 show characteristic bands related to their respective metal ions, but Dy-based 3 is very weak compared to Tb-based 2, indicating coordinating solvent molecules may be quenching Dy fluorescence.

Understanding the interactions between adsorbed gas molecules and a pore surface at molecular level is vital to exploration and attempts at rational development of gasselective nanoporous solids. Much current work focuses on the design of functionalized metal–organic frameworks (MOFs) or coordination networks (CNs) that selectively adsorb CO2. [1–9] While interactions between CO2 molecules and the p clouds of aromatic linkers in MOFs under ambient conditions have been explored theoretically, no direct structure evidence of such interactions are reported to date. Here we provide the first structural insight of such interactions in a porous calcium based CN using single-crystal X-ray diffraction methods, supported by powder diffraction coupled with differential scanning calorimetry (DSC-XRD), in situ IR/Raman spectroscopy, and molecular simulation data. We further postulate that such interactions are responsible for the high CO2/N2 adsorption selectivity, even in the case of a high relative humidity (RH). Our data suggest that the key interaction responsible for such selectivity, the room-temperature stability and the relative insensitivity to the RH of the CO2-CN adduct, is between two phenyl rings of the linker in the CN and the molecular quadrupole of CO2. The specific geometry of the linker molecule results in a “pocket” where carbon from the CO2 molecule is placed between two centroids of the aromatic ring. Our experimental confirmation of this variation on theoretically postulated interactions between CO2 and a phenyl ring will promote the search for other CNs containing phenyl ring pockets. Selective adsorption and sequestration of CO2 from sources of anthropogenic emissions, such as untreated waste from flue gas and products of the water gas shift reaction, is important to mitigate the growing level of atmospheric CO2. [10] Current separation methods use absorption in alkanolamine solutions, which are toxic, corrosive, and require significant energy for their regeneration. Hence microporous solid-state adsorbents, such as zeolites, hybrid zeolite–polymer systems, porous organic materials, and MOFs are proposed as alternatives, especially in combination with pressure swing processes. Rather than relying solely on tuning the pore diameters of microporous materials to select between gases based on size (the kinetic diameters of CO2, CH4 and N2 are 3.30, 3.76 3.64 , respectively ) selective separation relies on differences in electronic properties, such as the quadrupole moment and polarizability. Attempts to produce MOFs or CNs with adsorption properties competitive with those of commercially established aluminosilicate zeolites, relies on strategies that include pore surface modification with strongly polarizing functional groups, such as amines 7, 9,15] and desolvating metals centers 8, 16] to produce low-coordinated sites suitable for CO2 adsorption. The amine-functionalized materials offer a high selectivity toward CO2 adsorption, but a low effective surface area and thus, a low total uptake capacity. Strong interactions with polarizing functional groups, as well as with open metal sites presents other drawbacks including an increase in the costs for material regeneration. Furthermore, water effectively competes with CO2 at low-coordinated cation sites, impeding the performance of frameworks in commercial flue gas. We recently described a porous framework, CaSDB (SDB: sulfonyldibenzoate, compound 1) with a high CO2/N2 selectivity. At 0.15 bar of CO2 and 0.85 bar of N2, a typical composition of flue gas mixture from power plants, the selectivity is in the range of 48 to 85 at 298 K. CaSDB shows a reversible uptake of CO2 of 5.75 wt% at 273 K and 1 bar pressure and 4.37 wt% at room temperature, with heats of adsorption for CO2 and N2 of 31 and 19 kJmol , respectively. The as-synthesized compound contains not coordinated water molecules and is easily activated for gas adsorption by heating to 563 K in vacuum; remarkably the activated framework does not readsorb water, even if exposed to a RH greater than [*] A. M. Plonka, W. R. Woerner, Prof. Dr. J. B. Parise Department of Geosciences, Stony Brook University Stony Brook, NY 11794-2100 (USA) E-mail: john.parise@stonybrook.edu

Three new 3-D coordination networks were synthesized using alkaline-earth metal centers, calcium, and strontium, with 2,5-thiophenedicarboxylate (TDC) as the organic linker. [Ca2(TDC-2H)2(DMF)2]n [1, space group P21/n, a = 10.0704(3) A, b = 14.2521(3) A, c = 17.5644(6) A, β = 94.281(2)°] is composed of tetrameric calcium polyhedral clusters, which are connected by the organic linkers. Coordinated DMF molecules are present within the 1-D channel along the [010] direction. [Ca(TDC-2H)]n [2, space group Pbcm, a = 5.3331(5) A, b = 6.8981(4) A, c = 18.141(2) A] consists of chains of edge-sharing calcium octahedra, connected by organic linkers, to form a dense network. [Sr(TDC-2H)(DMF)]n [3, space group P21/n, a = 5.9795(3) A, b = 17.058(1) A, c = 11.3592(6) A, β = 91.257(1)°] forms a structural topology almost identical to compound 1 except that the chains are built by combinations of edge- and face-sharing polyhedra. Compounds 1 and 3 were synthesized using DMF as solvent, whereas compound 2 crystallizes usin...

Using different structural isomers (2,5-; 2,4-; 2;6-; 3,4-; 3,5-) of pyridinedicarboxylic acid, nine calcium-based coordination networks were synthesized under hydro-/solvothermal conditions and/or were produced via solvent recrystallization of previously synthesized compounds. The coordination networks reported were characterized using single crystal X-ray diffraction and thermal methods. They show diverse structural topologies, depending on the ligand geometry and coordinated solvent molecules, with inorganic connectivity motifs ranging from isolated octahedra to infinite chains, layer and a three-dimensional dense framework. The as-synthesized and desolvated networks further show structural transformation to hydrated phases through dissolution/reformation pathways. The process is likely driven by the high hydration energy of the calcium metal center.

A thermally stable, microporous calcium coordination network shows a reversible 5.75 wt % CO2 uptake at 273 K and 1 atm pressure, with an enthalpy of interaction of ∼31 kJ/mol and a CO2/N2 selectivity over 45 under ideal flue gas conditions. The absence of open metal sites in the activated material suggests a different mechanism for selectivity and high interaction energy compared to those for frameworks with open metal sites.

The title compound, [Mg(2)(C(12)H(14)O(4))(2)](n), is the first example of an s-block metal adamantanedicarboxylate coordination polymer. The asymmetric unit comprises two crystallographically unique Mg(II) centers and two adamantane-1,3-dicarboxylate ligands. The compound is constructed from a combination of chains of corner-sharing magnesium-centered polyhedra, parallel to the a axis, connected by organic linkers to form a layered polymer. The two Mg(II) centers are present in distorted tetrahedral and octahedral coordination environments derived from carboxylate O atoms. Tetrahedrally coordinated Mg(II) centers have been reported in organometallic compounds, but this is the first time that such coordination has been observed in a magnesium-based coordination polymer. The bond valance sums of the two Mg(II) centers are 2.05 and 2.11 valence units, matching well with the expected value of 2.

(H3O)LiSO4 is solvothermally synthesized from a mixture of LiNO3, 1,5-naphthalenedisulfonic acid tetrahydrate, and NH4F dissolved in DMF (autoclave, 100 °C, 4 d, 50% yield).

Minerals containing silicon in four-fold coordination (IVSi4+) are common in crustal rocks, while those involving six-coordinated silicon (VISi4+) dominate the Earth's lower mantle and determine its properties. Here we show a new type of phase transition determined by single-crystal high pressure X-ray diffraction experiments in a diamond anvil cell (DAC) using natural diopside (CaMgSi2O6), the archetypic member of clinopyroxene family, and one of the most abundant minerals of the Earth's upper mantle. Above 50 GPa at ambient temperature diopside transforms to a previously unknown post-clinopyroxene phase,β-diopside, with half of the tetrahedralIVSi4+ layers converted to octahedral VISi4+coordination. This phase is most probably a metastable state that is kinetically accessible at room temperature and the transformation is fully reversible on decompression. This new type of phase transition provides important clues to the exact mechanisms of breakdown of clinopyroxene in the Earth's mantle and may be expected to take place in other pyroxenes at pressures higher than previously explored.

The title compound, [Mg(2)(C(12)H(14)O(4))(2)](n), is the first example of an s-block metal adamantanedicarboxylate coordination polymer. The asymmetric unit comprises two crystallographically unique Mg(II) centers and two adamantane-1,3-dicarboxylate ligands. The compound is constructed from a combination of chains of corner-sharing magnesium-centered polyhedra, parallel to the a axis, connected by organic linkers to form a layered polymer. The two Mg(II) centers are present in distorted tetrahedral and octahedral coordination environments derived from carboxylate O atoms. Tetrahedrally coordinated Mg(II) centers have been reported in organometallic compounds, but this is the first time that such coordination has been observed in a magnesium-based coordination polymer. The bond valance sums of the two Mg(II) centers are 2.05 and 2.11 valence units, matching well with the expected value of 2.

Selective gas separation is one of the key properties exploited in industrial processes utilizing porous materials. The crystal structure of the native and activated frameworks, along with those of ion exchanged and otherwise modified variants, provide the basis for rational development of gas-selective nanoporous solids. In situ scattering studies of gas-loaded materials provide an understanding of the nature of interactions between sorbed gas and pore surface, which can be vital to development of reliable interatomic potentials, used simulating adsorption behavior. We find that simultaneous observation of the Differential Scanning Calorimetry coupled with x-ray diffraction (DSC-XRD) measurements is a particularly powerful tool 1, 2. The powder diffraction pattern can be monitored for changes, such as framework collapse, as porous materials are heated and activated. Apart from monitoring structural changes, thermal responses accompanying dynamic exposure to gases at variable humidity, and as the temperature is varied, provides a reliable tool in order to screen for new and potentially selective porous materials. The DSC signal provides a reliable means to determine the enthalpy of interaction between framework and gas, and there is experimental evidence this signal may distinguish between gas interactions with bare metal sites in the activated framework and other gas-framework interactions. Studies where the enthalpy of interaction and X-ray scattering from low angle peaks, which are most sensitive to the filling and evacuation of pores of the porous materials are monitored, can be coupled with varying the nature of the gas and the relative humidity. These studies are conveniently carried out with a modified gas manifold interfaced to a slightly modified Rigaku corporation DSC-XRD, which allows studies from about 150 – 600 K. Illustrative examples of the use of this laboratory based equipment, which provide the underpinnings of detailed single crystal studies of gas-loaded materials, include studies of porous calcium based coordination network (CaSDB, SDB: 4,4' - sulfonyldibenzoate), which is selective for CO2, even in the presence of high relative humidity (RH). Recent results from a series of materials studied in the home laboratory and at synchrotron sources will be presented.

Diiodobutadiyne forms cocrystals with bis(pyridyl)oxalamides, based on halogen bonds between the pyridine groups of the host and the iodoalkynes of the guest. These interactions align the diyne for topochemical polymerization to form poly(diiododiacetylene) or PIDA. To induce polymerization, the crystals are subjected to pressures of 3.5 GPa or above. Previously, we reported spectroscopic evidence of this pressure-induced polymerization, but attempts to recover single crystals after pressure treatment were unsuccessful. Here we present direct structural evidence of clean single-crystal to single-crystal polymerization in these cocrystals. The structure of the polymer cocrystal was solved from single-crystal diffraction data and is supported by high pressure in situ Raman spectroscopy. Careful analysis of the structural changes suggests that increasing pressure changes the packing of host molecules, and that the flexibility of the pyridine ring orientation enables the polymerization. The new sigma bonds of the polymer form at the expense of the halogen bonds in the starting cocrystal; after polymerization, the iodine atoms are no longer ideally located for strong halogen bonding with the host.

A microporous cadmium metal organic framework is synthesized and structurally characterized. The material possesses a 3-D framework with a 1-D sinusoidal chain and shows high selectivity for CO2 over N2. The selectivity is attributed to CO2 interacting with two phenyl rings of a V-shaped linker as estimated by the in situ XRD-DSC study.