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The use of s-block metal centers to construct coordination networks (CNs) is comparatively rare. The predominance of ionic forces and the absence of well-defined secondary building units make the rational construction of porous s-block CNs a challenging task. However, the nontoxic subset of these metals (Li, Na, K, Mg, Ca) based CNs, potentially useful for gas storage, separation, drug delivery, catalysis, and electrochemical applications, makes exploratory synthesis a worthwhile endeavor. In this review, we discuss the recent advances in the synthesis of s-block-CNs, produced using common carboxylic acid based linkers. [ABSTRACT FROM AUTHOR]

Two new Zn-based coordination polymers based polymers, namely, Zn7(TRZ)8(SIP)2·7H2O (1) and Zn5Na2(DMA)4(TRZ)4(SIP)4·5H2O (2) (TRZ 1,2,4-triazole, SIP sulfoisophthalate, and DMA dimethylamine), were synthesized under mild solvothermal conditions. Their crystal structures were characterized by single-crystal X-ray diffraction, and their thermal properties were examined by thermogravimetric analysis. Structure 1crystallizes in monoclinic P21/nspace group (a14.050(3) Å, b12.517(3) Å, c15.377(3) Å, 97.95(3)°, V2678.3(9) Å3, Z2), while structure 2is described as triclinic P(a9.701(2) Å, b12.442(3) Å, c17.218(3) Å, 89.83(3)°, 75.01(3)°, 73.33(3)°, V1917.5(7) Å3, Z1). Structure 1contains 8- and 16-membered channels made of Zn polyhedra linked by TRZ, which are occupied by water molecules and SIP ligands. Structure 2consists of one-dimensional chains of Zn−TRZ moieties that are linked to each other via SIP. It is a negatively charged open framework in which Naions and protonated dimethylamine in the cavities serve as counterions. [ABSTRACT FROM AUTHOR]

SrRuO3(SRO) has been studied extensively at the bulk and thin film scales for a variety of applications, such as multilayer devices, field-effect devices, multiferroics, and even ferroelectric random access memory (FeRAM). Conversely, the exploration of SRO nanoscale and submicrometer scale structures in terms of both synthesis and applications has been significantly limited. Herein, we are the first to report on the synthesis of SRO submicrometer-sized particles via a molten-salt method. We have accomplished this by systematically probing experimental parameters such as precursors, type of salt, annealing time, annealing temperature, surfactant, cooling rate, and reaction atmosphere in an effort to predictably control the resulting size, shape, and morphology of the SRO product particles. In particular, by quenching the reaction at a cooling rate of 100 °C/min, we can produce rounded SRO particles averaging 149 ± 100 nm in size. Moreover, with the addition of a mixture of mineral oil in Triton X-100, the final SRO particles are highly faceted, single-crystalline octahedra, averaging 126 ± 45 nm in size. Apart from the choice of molten salt which primarily controls chemical composition of SRO, we have determined the most important experimental parameter for shape and aggregation control is the surfactant, because of a combination of its hydrophobic and hydrophilic characteristics. We have found that the decomposition of the surfactant promotes the formation of SrCO3, which is consistent with the generation of SRO through the reaction of SrCO3with RuO2. Our successful syntheses have allowed us to explore physical properties, that is, magnetic and electronic, of these submicrometer-sized SRO particles, which are in good agreement with bulk SRO. Furthermore, we have also explored the potential of our as-synthesized particles as effective methanol oxidation reaction (MOR) catalysts for direct methanol fuel cells (DMFCs). Not only are our as-synthesized SRO particles MOR active but also our well-defined faceted octahedra exhibit a 4-fold increase in mass-activity and a 4-fold increase in surface area by comparison with the rounded particles, thereby emphasizing a clear advantage of faceted submicrometer SRO for electrochemical applications. [ABSTRACT FROM AUTHOR]

Protein cages such as ferritins and virus capsids have been used as containers to synthesize a wide variety of protein-templated inorganic nanoparticles. While identification of the inorganic crystal phase has been successful in some cases, very little is known about the detailed nanoscale structure of the inorganic component. We have used pair distribution function analysis of total X-ray scattering to measure the crystalline domain size in nanoparticles of ferrihydrite, γ-Fe2O3, Mn3O4, CoPt, and FePt grown inside 24-meric ferritin cages from H. sapiensand P. furiosus. The material properties of these protein-templated nanoparticles are influenced by processes at a variety of length scales: the chemistry of the material determines the precise arrangement of atoms at very short distances, while the interior volume of the protein cage constrains the maximum nanoparticle size attainable. At intermediate length scales, the size of coherent crystalline domains appears to be constrained by the arrangement of crystal nucleation sites on the interior of the cage. On the basis of these observations, some potential synthetic strategies for the control of crystalline domain size in protein-templated nanoparticles are suggested. [ABSTRACT FROM AUTHOR]

Chromium(III) (oxy)hydroxide and mixed Cr(III)−Fe(III) (oxy)hydroxides are environmentally important compounds for controlling chromium speciation and bioaccessibility in soils and aquatic systems and are also industrially important as precursors for materials and catalyst synthesis. However, direct characterization of the atomic arrangements of these materials is complicated because of their amorphous X-ray properties. This study involves synthesis of the complete Cr(III)−Fe(III) (oxy)hydroxide compositional series, and the use of complementary thermal, microscopic, spectroscopic, and scattering techniques for the evaluation of their structural properties. Thermal analysis results show that the Cr end member has a higher hydration state than the Fe end member, likely associated with the difference in water exchange rates in the first hydration spheres of Cr(III) and Fe(III). Three stages of weight loss are observed and are likely related to the loss of surface/structural water and hydroxyl groups. As compared to the Cr end member, the intermediate composition sample shows lower dehydration temperatures and a higher exothermic transition temperature. XANES analysis shows Cr(III) and Fe(III) to be the dominant oxidation states. XANES spectra also show progressive changes in the local structure around Cr and Fe atoms over the series. Pair distribution function (PDF) analysis of synchrotron X-ray total scattering data shows that the Fe end member is nanocrystalline ferrihydrite with an intermediate-range order and average coherent domain size of ∼27 Å. The Cr end member, with a coherent domain size of ∼10 Å, has only short-range order. The PDFs show progressive structural changes across the compositional series. High-resolution transmission electron microscopy (HRTEM) results also show the loss of structural order with increasing Cr content. These observations provide strong structural evidence of chemical substitution and progressive structural changes along the compositional series. [ABSTRACT FROM AUTHOR]

A 3-D lithium based metal organic framework Li2(C7H3NO4)·(C3H7NO) [Li2(2,5-PDC)·(DMF), 1; ULMOF-5, UL= ultralight, PDC = pyridinedicarboxylate, space group Pbcn,a= 15.800(3) Å, b= 8.5958(17) Å, c= 18.460(4) Å, V= 2507.1(9) Å3] was synthesized using the solvothermal method and characterized by single crystal and powder X-ray diffraction techniques. Compound 1contains tetrameric edge and corner sharing lithium polyhedral clusters connected by organic linkers, forming channels along the [001] direction, with coordinated DMF molecules pointing toward each other in these channels. Thermogravimetric analysis shows compound 1is stable up to 280 °C under N2atmosphere followed by removal of the coordinated DMF molecules, as evident from the associated weight loss. BET (25.06 m2/g) surface area measurement showed loss of porosity after solvent removal because of a structure change. Solid-state 6Li NMR on the desolvated compound showed the absence of tricoordinated lithium centers, indicating rearrangement of bonds around the lithium center after DMF removal. The desolvated form reverts to the original form upon exposure to DMF, showing dynamic structural behavior. [ABSTRACT FROM AUTHOR]

Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 Å and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H 2O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection. [ABSTRACT FROM AUTHOR]

Four new coordination polymer compounds have been prepared using 3-amino-1,2,4-triazole (AmTRZ) as an organic linker, namely, ZnCl(AmTRZ) (1), Zn(HCO2)(AmTRZ) (2), Zn5(OH)2(AmTRZ)6(NO3)2·6H2O (3), and Zn5(OH)(AmTRZH)(AmTRZ)6(HCO2)3·5H2O (4). They were synthesized under mild hydro- or solvothermal conditions using water or dimethylformamide as solvent. Their crystal structures were characterized by single-crystal X-ray diffraction techniques, and thermal properties of all compounds were examined by thermogravimetric analysis. Isostructural compounds 1and 2(Pbca, a9.389(1) Å, b10.115(1) Å, c11.571(2) Å, V1098.9(3) Å3, Z8 for 1and a9.198(1) Å, b10.341(1) Å, c12.577(2) Å, V1196.2(3) Å, Z8 for 2) display a two-dimensional layer structure where Zn centers are linked by AmTRZ molecules to form gridlike layers containing eight-membered rings. Structure 3(Pa, a15.0448(6) Å, V3405.3(2) Å3, Z4) is a dense three-dimensional framework, featuring seven-membered channels where water and nitrate anions are located. Structure 4(I4/m, a19.2576(9) Å, c20.286(2) Å, V7523.2(9) Å3, Z8) is built from porous Zn−AmTRZ layers containing 12- and 8-membered rings, which are connected to each other by dinuclear Zn tetrahedra building units. Water and formate anions occupy the void inside the framework. [ABSTRACT FROM AUTHOR]

A Li7K salt of Nb6O198-and a Li13K salt of SiNb12(OH)2O3814-have been prepared and characterized by single-crystal X-ray diffraction and 6Li MAS NMR. The structure of Li7KNb6O19·15H2O (a9.859(10) Å, b17.500(17) Å, c17.384(17) Å, 91.609(16)°, monoclinic, P21/c, R1 4.94% based on 5343 reflections) consists of a super-octahedron of six edge-sharing NbO6octahedra capped by a Li4O10adamantane-like structure. The 6Li MAS NMR data are consistent with five tetrahedral Lisites ( 0.20 ppm) and two octahedral Lisites ( −1.38 ppm). The reaction of Li7KNb6O19·15H2O and Si(OC2H5)4yields Li13KSiNb12(OH)2O38·17H2O (a20.341(4) Å, b10.735(2) Å, c21.438(4) Å, 105.41(3)°, monoclinic, P21/c, R1 6.49% based on 6161 reflections), an -Keggin ion (SiNb12(OH)2O3814-) linked by Lications and a single Kcation. Interpretation of structural data suggests that Lihas weaker ion pairing to Nb6O198-in the solid state than do Na, K, Rb, or Cs(i.e., ion pairing increases with an increase in the ionic radius of the alkali metal cation). Given the high charge density of Nb6O198-, the increase in solubility of alkali salts of Nb6O198-in water from Lito Cs(Li< Na< K< Rb< Cs) suggests that similar ion pairing in solution decreases the effective charge of the polyanion and increases stability as long as charge neutralization is not achieved. In addition, Lifacilitates the formation of discrete SiNb12(OH)2O3814-clusters from a Nb6O198-precursor; the analogous reaction with Na7HNb6O19produces a Keggin chain material. [ABSTRACT FROM AUTHOR]

Two new metal−organic framework compounds were synthesized under solvothermal conditions using Zn2ion, 1,2,4-triazole (TRZ), and 1,4- and 2,6-naphthalenedicarboxylic acids (NDC):  Zn4(TRZ)4(1,4-NDC)2·2DMF·2H2O (1) and Zn4(TRZ)4(2,6-NDC)2·2DMF·4H2O (2). Their crystal structures were characterized by single-crystal X-ray diffraction. Structure 1crystallizes in the P21/nspace group with a13.609(2) Å, b27.181(5) Å, c13.617(3) Å, 92.46(1) °, V5032.4(16) Å3, and Z4. Structure 2crystallizes in orthorhombic Pna21space group with a30.978(6) Å, b12.620(3) Å, c13.339(3) Å, V5215(2) Å3, and Z4. Both structures are analogues of the previously reported Zn4(TRZ)4(1,4-BDC)2·16H2O where the layers of Zn−triazole moieties are pillared by aromatic dicarboxylates to create 3-D open frameworks. Nitrogen sorption studies revealed that these structures have Brunaer−Emmett−Teller (BET) surface areas of 362.1−584.1 m2/g. Hydrogen sorption experiments showed they can store 0.84−1.09 wt % of H2at 77 K and 1 atm. Although they do not contain large pores or surface areas, they possess the hydrogen sorption capacities comparable to those of highly porous metal−organic frameworks. [ABSTRACT FROM AUTHOR]

Pair distribution function studies using X-ray scattering data from zeolite Na-A samples treated at pressure up to 8 GPa indicate a pressure-induced amorphisation mechanism involving loss of crystallographic order of the aluminosilicate framework but retention of the local sodium to oxygen bonding. [ABSTRACT FROM AUTHOR]