A mesoporous solid with crystalline walls and an ordered pore structure exhibiting a bimodal pore size distribution (3.3 and 11 nm diameter pores) has been synthesized. Previous attempts to synthesize solids with large ordered mesopores by hard templating focused on the preparation of templates with thick walls (the thick walls become the pores in the target materials), something that has proved difficult to achieve. Here the large pores (11 nm) do not depend on the synthesis of a template with thick walls but instead on controlling the microporous bridging between the two sets of mesopores in the KIT-6 template. Such control determines the relative proportion of the two pore sizes. The wall thickness of the 3D cubic NiO mesopore has also been varied. Preliminary magnetic characterization indicates the freezing of uncompensated moments or blocking of superparamagnetism.

Organisms have the ability to produce structures with superior characteristics as in the course of biomineralization. One of the most intriguing characteristics of biominerals is the existence of intracrystalline macromolecules.Despite several studies over the last two decades and efforts to mimic the incoporation of macromolecules synthetically, a fundamental understanding of the mechanism of incorporation is as yet lacking. For example, which of the common 20 amino acids are really responsible for the interaction with the mineral phase? Here a reductionist approach, based on high-resolution synchrotron powder diffraction and analytical chemistry, is utilized to screen all of these amino acids in terms of their incorporation into calcite. We showed that the important factors are amino-acid charge, size, rigidity and the relative pKa of the carboxyl and amino functional groups. It is also demonstrated that cysteine, surprisingly, interacts very strongly with the mineral phase and therefore, like acidic amino acids, becomes richly incorporated. The insights gained from this study shed new light on the incorporation of organic molecules into an inorganic host in general, and in particular on the biomineralization process.

LiMn 2 O 4 spinel is one of the most important intercalation electrodes for rechargeable lithium batteries at the present time. [1][2][3][4] It combines the highest intrinsic rate capability of the well-known intercalation cathodes with high safety, low toxicity, and low cost, making it attractive for high-power applications, such as hybrid electric vehicles. [5][6][7][8][9][10][11] However, the drawback of this electrode is its slow dissolution in the electrolyte present in the lithium-ion battery. To mitigate such dissolution, recent interest has focused on highly lithium-rich compositions in the region of Li 1. [11,12] Consequently, high rate capability becomes even more important to ensure high utilization of the reduced theoretical capacity. Here we describe the synthesis of an ordered mesoporous Li 1.12 Mn 1.88 O 4 spinel and show that it combines higher rate capability than the corresponding bulk material (50 % higher specific capacity at a rate of 30C, 3000 mA g À1 ) at ambient temperature with good stability at elevated temperatures, despite a high surface area of 90 m 2 g À1 and without the need for deliberate coating or doping with foreign ions. [13,14] Furthermore, when cycled over a wide voltage range (including the 3 V and 4 V plateaus) the mesoporous material exhibits improved capacity retention compared to the bulk spinel. This capacity retention is because of the nanometer thin walls between the pores that render the cubic/tetragonal phase transformation more facile in the mesoporous spinel than in the bulk phase. The potential advantages of using nanostuctured electrode materials, in this case mesoporous solids, over nanoparticles are discussed.Ordered mesoporous Li 1+x Mn 2Àx O 4 spinel is synthesized for the first time, as described in detail in the Experimental Section, by a hard templating route with post-template treatment .[ [15][16][17][18][19] Briefly, an aqueous solution of Mn(NO 3 ) 2 was infiltrated into the ordered 3D pore structure of the mesoporous silica, KIT-6. Heating in air converted the precursor into Mn 2 O 3 . Following the removal of the SiO 2 template, the replica 3D mesoporous Mn 2 O 3 was transformed to Mn 3 O 4 spinel by heating in a reducing atmosphere, which then reacted with LiOH to form mesoporous LiMn 2 O 4 spinel (Figure 1). It is remarkably that throughout the solid-state transformations Mn 2 O 3 !Mn 3 O 4 !LiMn 2 O 4 , the ordered 3D mesoporous structure was preserved (Figure 1), demonstrating that the thin walls of the mesopore (7 nm thick) can accommodate the strain of multiple solid-solid phase transformations. The mesoporous structure exists throughout the material, as demonstrated by examining many particles using

Mesoporous transition metal oxides have attracted much attention recently.[1] The synthesis of mesoporous solids usually demands a templating approach. [1,2] Soft templates (surfactants) yield ordered mesopores with non-crystalline walls. [2,3] The use of hard templates (e.g., mesoporous silica) results in sufficiently high processing temperatures to yield ordered mesopores with crystalline walls. [4,5] However, when used to synthesize transition metal oxides, both methods are restricted in the oxidation states that are accessible.[ Figure 1, confirm the formation of an ordered pore structure for Mn 2 O 3 and its retention on conversion to Mn 3 O 4 . The pore structure replicates that of the KIT-6 template, space group Ia-3d. Examining many different particles demonstrated that the mesoporous structure is presented throughout each material. The unit cell parameters, a 0 , extracted from the TEM data, are 25.1 and 24.9 nm for mesoporous Mn 2 O 3 and Mn 3 O 4 , respectively. These data indicate that the mesostructure is preserved despite conversion from Mn 2 O 3 to Mn 3 O 4 . Low-angle powder X-ray diffraction (PXRD) patterns (Figure 2) for both mesoporous materials exhibit one sharp peak at ∼ 0.9°, which could be indexed as the [211] reflection in the Ia-3d space group and one broad peak at 1.7-1.8°, further demonstrating the ordered mesostructures. The d-values calculated from the first peak are 101.2 and 101.0 Å, which correspond to the unit cell parameters, a 0 , 24.8 and 24.7 nm for mesoporous Mn 2 O 3 and Mn 3 O 4 , respectively. These values are in good agreement with the TEM results.The mesostructures were further confirmed by nitrogen adsorption-desorption measurements. Type IV isotherms ( Fig. 3a and b)

Porous NOTT-202a shows exceptionally high uptake of SO2, 13.6 mmol g(-1) (87.0 wt %) at 268 K and 1.0 bar, representing the highest value reported to date for a framework material. NOTT-202a undergoes a distinct irreversible framework phase transition upon SO2 uptake at 268-283 K to give NOTT-202b which has enhanced stability due to the formation of strong π···π interactions between interpenetrated networks.

We present a unique study of the frustrated spinel MgV2O4 which possesses highly coupled spin, lattice and orbital degrees of freedom. Using large single-crystal and powder samples, we find a distortion from spinel at room temperature (space group F 43m) which allows for a greater trigonal distortion of the VO6 octahedra and a low temperature space group (I4m2) that maintains the mirror plane symmetry. The magnetic structure that develops below 42 K consists of antiferromagnetic chains with a strongly reduced moment while inelastic neutron scattering reveals one-dimensional behavior and a single band of excitations. The implications of these results are discussed in terms of various orbital ordering scenarios. We conclude that although spin-orbit coupling must be significant to maintain the mirror plane symmetry, the trigonal distortion is large enough to mix the 3d levels leading to a wave function of mixed real and complex orbitals. PACS numbers: 75.25.+z,75.10.Jm, 61.12.Ex Geometrically frustrated magnets are characterized by competing interactions resulting in a highly degenerate lowest energy manifold. In many cases the degeneracy is eventually lifted at low temperatures by a lattice distortion. In compounds where the magnetic ions also possess orbital degeneracy, orbital-ordering can influence the exchange interactions and lift the frustration. The vanadium spinels AV 2 O 4 , where A is diamagnetic Cd 2+ , Zn 2+ , or Mg 2+ provide ideal systems to study the interactions between spin, lattice and orbital degrees of freedom [1]. In these compounds the magnetic V 3+ -ions possess orbital degeneracy and form a frustrated pyrochlore lattice with direct exchange interactions between nearest neighbors providing a direct coupling to the orbital configuration. The interplay of orbital and spin physics has been studied in other systems like the perovskite vanadates (RVO 3 , R is a rare earth) which show a strong correlation between orbital ordering and magnetic structure [2]. However in these compounds the couplings are unfrustrated and indirect, occurring via super exchange through oxygen. In contrast the magnetic structure and excitations in the spinel vanadates are more sensitive to orbital ordering and thus characteristic of it. Furthermore the additional component of frustration allows for the possibility of exotic ground states. Indeed the nature of the ground state in the spinel compounds has generated intense theoretical interest over the past eight years [4-7] but has remained an unresolved experimental issue which we will address in this paper.The electronic configuration of V 3+ is 3d 2 leading to a single-ion spin S=1. Each V 3+ -ion is located at the center of edge sharing VO 6 octahedra which create a crystal-field that splits the d-orbitals and lowers the energy of the three t 2g orbitals by approximately 2.5 eV [3].These levels are usually assumed to be degenerate (ignoring the small trigonal distortion which will be discussed later) so that the two d-electrons of V 3+ randomly occupy the three t 2...

Variable temperature neutron diffraction was carried out on mesoporous R-Fe 2 O 3 (hematite) with a mean pore diameter of 38.5 Å. Data were directly compared to measurements carried out on bulk hematite. Unlike bulk hematite, the mesoporous material does not undergo a spin-flop transition from a weak ferromagnet to a pure antiferromagnet (Morin transition, T M ) 259.1(2)). Instead, the material remains a weak ferromagnet down to 2 K with the magnetic moments staying perpendicular to the R3 j c [111] ([003] in the hexagonal cell) direction rather than realigning (to) almost parallel to this direction. The angle of the magnetic Fe 3+ moments to the [111] direction in the antiferromagnetic state also accurately was obtained for bulk hematite. Using magnetic hysteresis measurements, the canting angle responsible for weak ferromagnetism within the ab planes (hexagonal setting) was deduced for the mesoporous material at 12 K and compared to the angle made in bulk hematite above T M .

We report a combined experimental and theoretical investigation of the layered antimonide PrMnSbO which is isostructural to the parent phase of the iron pnictide superconductors. We find linear resistivity near room temperature and Fermi liquid-like T^{2} behaviour below 150 K. Neutron powder diffraction shows that unfrustrated C-type Mn magnetic order develops below \sim 230 K, followed by a spin-flop coupled to induced Pr order. At T \sim 35 K, we find a tetragonal to orthorhombic (T-O) transition. First principles calculations show that the large magnetic moments observed in this metallic compound are of local origin. Our results are thus inconsistent with either the itinerant or frustrated models proposed for symmetry breaking in the iron pnictides. We show that PrMnSbO is instead a rare example of a metal where structural distortions are driven by f-electron degrees of freedom