Inorganic Framework Materials Research Articles

Low-Frequency Vibrational Spectra of 4-Fluorophenol Studied by THz Spectroscopy and Solid-State Density Functional Theory.

Hydrogen bonds serve as important intermolecular interactions organizing the spatial arrangement of molecular crystals. Determining the hydrogen-bond orientations remains a challenging task. In the previous XRD study, the authors assumed a single crystal structure of 4-fluorophenol in which molecules form hexamer-ring clusters via anticlockwise hydrogen bonding. However, the existence of the other structure, which adopts clockwise hydrogen bonding, remains uncertain and warrants further exploration. We unveil distinctive fingerprint information associated with both structures by using high-resolution terahertz spectroscopy. The distinct structures result in different intramolecular geometries of 4-fluorophenol regarding the O-H bond configurations, which are manifested by a noticeable peak splitting in the 20-200 cm-1 frequency range. This result illustrates the sensitivity of THz spectroscopy to hydrogen-bond conformational polymorphism. Our findings represent a significant advancement in utilizing high-resolution THz spectroscopy to resolve hydrogen-bond orientations in molecular crystals with possible broad applicability across diverse hydrogen-bonded organic and inorganic framework materials.

Hydroxylated Polyoxometalate with Cu(II)- and Cu(I)-Aqua Complexes: A Bifunctional Catalyst for Electrocatalytic Water Splitting at Neutral pH.

A sole inorganic framework material [Li(H2O)4][{CuI(H2O)1.5} {CuII(H2O)3}2{WVI12O36(OH)6}]·N2·H2S·3H2O (1) consisting of a hydroxylated polyoxometalate (POM) anion, {WVI12O36(OH)6}6-, a mixed-valent Cu(II)- and Cu(I)-aqua cationic complex species, [{CuI(H2O)1.5}{CuII(H2O)3}2]5+, a Li(I)-aqua complex cation, and three solvent molecules, has been synthesized and structurally characterized. During its synthesis, the POM cluster anion gets functionalized with six hydroxyl groups, i.e., six WVI-OH groups per cluster unit. Moreover, structural and spectral analyses have shown the presence of H2S and N2 molecules in the concerned crystal lattice, formed from "sulfate-reducing ammonium oxidation (SRAO)". Compound 1 functions as a bifunctional electrocatalyst exhibiting oxygen evolution reaction (OER) by water oxidation and hydrogen evolution reaction (HER) by water reduction at the neutral pH. We could identify that the hydroxylated POM anion and copper-aqua complex cations are the functional sites for HER and OER, respectively. The overpotential, required to achieve a current density of 1 mA/cm2 in the case of HER (water reduction), is found to be 443 mV with a Faradaic efficiency of 84% and a turnover frequency of 4.66 s-1. In the case of OER (water oxidation), the overpotential needed to achieve a current density of 1 mA/cm2 is obtained to be 418 mV with a Faradaic efficiency of 80% and turnover frequency of 2.81 s-1. Diverse electrochemical controlled experiments have been performed to conclude that the title POM-based material functions as a true bifunctional catalyst for electrocatalytic HER as well as OER at the neutral pH without catalyst reconstruction.

The missing link between zeolites and polyoxometalates.

Open framework materials such as zeolites and metalorganic frameworks are garnering tremendous interest because of their intriguing architecture and attractive functionalities. Thus, new types of open framework materials are highly sought after. Here, we present the discovery of completely new inorganic framework materials, where, in contrast to conventional inorganic open frameworks, the scaffold is not based on tetrahedral EO4 (E = main group element) but octahedral MO6 (M = transition metal) building blocks. These structural features place them closer to polyoxometalates than zeolites. The first representatives of this class of materials are [(R)24(NH4)14(PO(OH)2)6]·[M134(PO3(OH,F))96F120] (M = Co, R = C2Py = 1-ethylpyridinium and M = Ni, R = C4C1Py = 1-butyl-3-methylpyridinium) featuring interlinked fullerene-like nanosphere cavities. Having a transition metal building up the framework brings about interesting properties, for example, spin-glass behavior, and, with this particular topology, a hedgehog-like spin orientation.

Hybrid Ceramic Solid State Electrolyte for High Performance Solid State Batteries

There is a global demand for high energy storage systems for portable consumer devices such as cell phones, laptops, including electric vehicles. Lithium ion batteries (LIBs) are the most promising options due to the high volumetric, gravimetric energy, and power densities. Current LIBs using LiCoO2, LiNiO2, LiMnO4, and LiFePO4 cathodes coupled with a graphite anode exhibit a power density of 100-260 Whkg-1 [1]. With the advent of high capacity Li – S system, efforts are focused on replacing low capacity carbon based anodes with Li metal and composite systems. However, the Li metal plating process on Cu/Li substrates shows undesirable performance due to unstable Li plating leading to formation of high surface area Li, loss of Li due to uneven plating/deplating, increase in internal resistance and formation of the deleterious Li dendrites [2-4]. These characteristic plating phenomena, result in low columbic efficiencies, increase in plating/deplating potentials as well as ensuing hysteresis losses. As a result, there is rapid fade in specific capacity/energy density combined with thermal run away due to either increased internal resistance or internal short-circuiting of the cell due to the formation and growth of unwanted dendrites running the risk of explosive failure of the cells. Novel hybrid ceramic electrolytes (HCE) were developed utilizing Inorganic Framework Materials Networks (IFM) with enhanced Li+ diffusion utilizing the low activation energy for surface migration. The crystallographic channels in the inorganic framework provide pathways for efficient transport of Li+ ions thus making them attractive ceramic electrolyte materials. The ionic conductivity measurements of these ceramic electrolytes were conducted in Li/Li symmetric CR2025 coin cell. These novel ceramic electrolytes show a Li+ conductivity of ~ 1.26 x 10-4 S/cm. Subsequently the coin cells were cycled at different current densities ranging from 0.5mA/cm2 to 4mA/cm2 and their plating/deplating over-potentials were recorded and analyzed. These hybrid ceramic electrolytes show low plating/deplating potentials ranging from 100mV@1mA/cm2 – 450mV @4mA/cm2 comparable with garnet based solid state electrolytes. Subsequently, the electrolytes were tested for electrochemical performance against Cu and new high interfacial energy alloy based collect collectors identified in a coin cell and their coulombic efficiency recorded. The hybrid ceramic electrolytes show columbic efficiency of ~97-99% for a constant plating and deplating current density of 0.5mA/cm2 for 1h (charge density~0.5mAh/cm2) when tested with Cu electrodes. The full cell electrochemical performance, SEM analysis of plated and deplated electrodes, combined with Raman and infrared spectroscopy results will be presented and discussed. Figure 1

Technetium Encapsulation by A Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7).

Technetium (99Tc) is an important long-lived radionuclide released from various activities including nuclear waste processing, nuclear accidents and atmospheric nuclear weapon testing. The removal of 99Tc from the environment is a challenging task, and chemical capture by stable ceramic host systems is an efficient strategy to minimise the hazard. Here we use density functional theory with dispersion correction (DFT+D) to examine the capability of the porous inorganic framework material C12A7 that can be used as a filter material in different places such as industries and nuclear power stations to encapsulate Tc in the form of atoms and dimers. The present study shows that both the stoichiometric and electride forms of C12A7 strongly encapsulate a single Tc atom. The electride form exhibits a significant enhancement in the encapsulation. Although the second Tc encapsulation is also energetically favourable in both forms, the two Tc atoms prefer to aggregate, forming a dimer.

In situ solid-state NMR and XRD studies of the ADOR process and the unusual structure of zeolite IPC-6.

The assembly-disassembly-organization-reassembly (ADOR) mechanism is a recent method for preparing inorganic framework materials and, in particular, zeolites. This flexible approach has enabled the synthesis of isoreticular families of zeolites with unprecedented continuous control over porosity, and the design and preparation of materials that would have been difficult-or even impossible-to obtain using traditional hydrothermal techniques. Applying the ADOR process to a parent zeolite with the UTL framework topology, for example, has led to six previously unknown zeolites (named IPC-n, where n = 2, 4, 6, 7, 9 and 10). To realize the full potential of the ADOR method, however, a further understanding of the complex mechanism at play is needed. Here, we probe the disassembly, organization and reassembly steps of the ADOR process through a combination of in situ solid-state NMR spectroscopy and powder X-ray diffraction experiments. We further use the insight gained to explain the formation of the unusual structure of zeolite IPC-6.

Polyamine-Cladded 18-Ring-Channel Gallium Phosphites with High-Capacity Hydrogen Adsorption and Carbon Dioxide Capture.

In this study, we synthesized a unique inorganic framework bearing the largest 18-membered-ring channels in gallium phosphites, denoted as NTHU-15, which displayed genuine porosity even though large organic templates were present. The idea of using the "template-cladded" strategy succeeded in releasing channel space of up to ∼24% of the unit-cell volume as highly positive-charged organic templates were manipulated to cling to the anionic inorganic walls. NTHU-15 showed both high H2 uptake of 3.8 mmol/g at 77 K and effective CO2 adsorption of ∼2.4 mmol/g at 298 K, which surpassed those of all other known extra-large-channel inorganic framework structures. NTHU-15 has been successful at overcoming the long-standing problem of organic-templated extra-large-channel structures as opposed to a "true open" framework. Moreover, it realized practical gas sorption functionality in innovated metal phosphites. In view of its high stability in hot water and high selectivity for CO2 adsorption, NTHU-15 may be the first novel inorganic framework material to be applied to the field of flue gas cleaning.

Shape-stabilised n-octadecane/activated carbon nanocomposite phase change material for thermal energy storage

A shape-stabilised n-octadecane/activated carbon nanocomposite was successfully prepared using a one-step impregnation method. Activated carbon (AC) was used as an inorganic framework material, and n-octadecane was used as a phase change material (PCM) for thermal energy storage. The mass loading percentage of n-octadecane in the PCM nanocomposites which was determined using DSC is 42.5 wt.%, due to the excellent adsorption ability of AC. Field Emission Scanning Electron Microscope (FESEM) images and nitrogen adsorption–desorption results for the nanocomposites PCM indicate that n-octadecane was uniformly adsorbed into the pores of AC. The porous networks of the AC prevented leakage of the melted n-octadecane during the phase change processes. The performance of the n-octadecane/AC nanocomposites as a thermal energy storage material for building applications was examined by incorporation of the nanocomposite with gypsum to function as a panel board. The results indicate that the incorporation of the n-octadecane/AC nanocomposites in gypsum board lowered the indoor temperature fluctuation of the buildings, which could reduce energy consumption.

A brilliant cryogenic magnetic coolant: magnetic and magnetocaloric study of ferromagnetically coupled GdF3

The magnetocaloric effect of an inorganic framework material with repeating GdF3 units has been studied using isothermal magnetization and heat capacity measurements.

Insights into the Self-Assembly Mechanism of the Modular Polyoxometalate “Keggin-Net” Family of Framework Materials and Their Electronic Properties

The mechanism for the syntheses of inorganic framework materials based solely on polyoxometalate Keggin clusters has been examined and their electronic properties have been investigated. The assembly of the modular network compounds with the molecular formula (C4H10NO)n[W72M12O268X7] (with the heteroatom X = Si or Ge and the heterometal M = Co(II) or Mn(III)) is based on the isomerization of the metastable precursor material [γ-XW10O36]8–, followed by the inclusion of the heterometal and subsequent assembly into the extended framework structure. The two frameworks featuring manganese substitution can be dis- and reassembled in a recrystallization process while the cobalt versions do not show comparable behavior. The intrinsic differences of the four compounds with regards to their heteroatom and heterometal substitution are shown in terms of their redox behavior.

Spontaneous Self-Assembly of Silica Nanocages into Inorganic Framework Materials

The possibility of the formation of different silica nanostructures based on fully coordinated spheroidal nanocages (SiO2)24 is theoretically investigated using a pairwise potential and the ReaxFFSiO reactive force field. Molecular dynamics simulations at T = 300 K predict that while these nanocages are thermally stable, they spontaneously undergo dimerization upon contact by forming two siloxane bridges. The corresponding reaction pathways obtained with both methods are quantitatively confirmed by electronic structure calculations performed at the Hartree-Fock and density functional theory levels. The barrierless dimerization of silica nanocages is the first step of subsequent polymerizations into strongly bound inorganic materials. Routes to polymerization and possible applications are discussed.

ChemInform Abstract: Using 17O Solid‐State NMR and First Principles Calculation to Characterize Structure and Dynamics in Inorganic Framework Materials

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Using17O solid-state NMR and first principles calculation to characterise structure and dynamics in inorganic framework materials

The use of solid-state (17)O NMR to determine local chemical environment and to characterise oxygen dynamics is illustrated in studies of zirconium tungstate, ZrW(2)O(8), and tungsten oxide, WO(3). Simple 1D magic-angle spinning (MAS) NMR allows the chemical environments in ZrW(2)O(8) to be readily characterised, and the use of a combination of one- and two-dimensional experiments to characterise oxygen dynamics in its cubic phase is reviewed. Combining local information about structure and dynamics from NMR with long-range structural information from diffraction allows a comprehensive picture of the material to be developed. Recent work is described that uses first principles calculation of NMR parameters to probe subtle asymmetries in the WO(6) octahedra that form the structural motif in WO(3). NMR is shown to be a highly sensitive probe of local structure, allowing different models derived from high-quality neutron diffraction studies to be distinguished. The density functional theory (DFT) calculations allow clear correlations between (17)O chemical shifts and distortions of the structure to be established.

Magic Silica Clusters as Nanoscale Building Units for Super-(Tris)tetrahedral Materials

For bridging between the building block and the bulk, we consider the assembly of highly stable (SiO2)8 “magic” clusters into inorganic framework materials. Our cluster building blocks are predicted to be strongly energetically preferred while also having the propensity to form intercluster siloxane (Si−O−Si) bridges. Silicate framework materials are thus proposed with their viability judged via state-of-the-art density functional calculations. All frameworks differ from known synthesized materials with the most stable frameworks lying in a thermodynamically accessible window shared by mesoporous silicas. A few frameworks also correspond to hypothetical frameworks discovered through top-down mathematical approaches providing a link between high-level searches and our bottom-up constructive approach. We predict that the gas-phase deposition of magic clusters will potentially allow the fabrication of new framework materials not readily achievable through traditional hydrothermal syntheses.

Rational design of the pore system within the framework aluminium alkylenediphosphonate series.

We report here on the solvothermal synthesis and crystal structure of the hybrid organic-inorganic framework material Al(2)[O(3)PC(3)H(6)PO(3)](H(2)O)(2)F(2).H(2)O (orthorhombic, Pmmn, a = 12.0591(2) A, b = 19.1647(5) A, c = 4.91142(7) A, Z = 4), the second member of the Al(2)[O(3)PC(n)H(2n)PO(3)](H(2)O)(2)F(2).H(2)O series. The structure consists of corrugated chains of corner-sharing AlO(4)F(2) octahedra in which alternating AlO(4)F(2) octahedra contain two fluorine atoms in a trans or a cis configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the propylene groups to form a three-dimensional framework structure containing a one-dimensional channel system. The linkage of the corrugated inorganic Al-O-P layers within the structure results in the formation of two types of channel that differ in size, shape and composition. The smaller channel is unoccupied; the larger channel is more elongated and contains two extra-framework water molecules per unit cell. A computational investigation into the driving force that controls the stacking arrangement of the Al-O-P inorganic layers within this series of compounds reveals that the stacking is found to be controlled by thermodynamic factors, arising chiefly from the conformation of the organic linker molecule used to connect the inorganic sheets. It is found that the registration of the inorganic layers can be engineered by selecting an appropriate, simple organic spacer or linker alkyl chain, where an even number of carbon atoms in the alkyl chain directs formation of aligned, stacked, inorganic sheets (AAAAAA), and an odd number directs formation of unaligned, stacked sheets (ABABAB) and the formation of one or two channel types in the resultant structure, respectively. This combination of alkyl-chain linkers in conjunction with corrugated inorganic layers is an effective tool to rationally design the pore system of hybrid framework materials.

Identification of a Near‐Linear Supramolecular Water Dimer, (H2O)2, in the Channel of an Inorganic Framework Material.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Identification of a Near-Linear Supramolecular Water Dimer, (H2O)2, in the Channel of an Inorganic Framework Material

Supramolecular water dimer, (H(2)O)(2), is fundamentally important. During the course of our work on polyoxometalates, we have been able to identify the existence of hydrogen-bonded, near-linear water dimers in the "sinuous" channels of an inorganic framework material, Na(3)(n)(H(2)O)(6)(n)[Al(OH)(6)Mo(6)O(18)](n)() x 2nH(2)O, 1. The three-dimensional network structure of 1 in the solid state is assembled by the Anderson type of heteropolyanions as building blocks sharing sodium cations. Vibrational spectroscopy, X-ray powder diffraction technique, TG-DSC analyses, and single-crystal X-ray structure analysis have characterized this host-guest system, 1. Crystal data for 1: triclinic space group Ponemacr;, a = 12.0618 (3) A, b = 13.1570 (4) A, c = 14.1563 (4) A, alpha = 80.7850 (10) degrees, beta = 75.2660 (10) degrees, gamma = 68.9210 (10) degrees, and Z = 3.

Cu(2-methylpyrazine-5-carboxylate) 2 hydrate: a metal-containing-ligand for the construction of organic–inorganic framework materials. Four new one-, two- and three-dimensional mixed-valent Cu I–Cu II coordination polymers

The copper containing building block, Cu(C 6H 5N 2O 2) 2·H 2O ( 1) was used in the synthesis of four new mixed-valent organic–inorganic coordination polymers, each of which adopted a different structural motif. Synthesis, X-ray structure determinations, thermogravimetric analyses and magnetic properties are presented. The reaction between 1 and CdCl 2 afforded a one-dimensional chain structure, [Cu(C 6H 5N 2O 2) 2(H 2O) 2Cu 2Cl 2(H 2O) 2] n ( 2). When CdCl 2 was replaced by CuCl, the reaction yielded a polymer, [Cu(C 6H 5N 2O 2) 2(H 2O) 2Cu 2Cl 2(H 2O) 2] n having the same empirical formula, but a completely different two-dimensional framework ( 3). The reaction of CdBr 2 and 1 resulted in the formation of two different coordination polymers: [Cu(C 6H 5N 2O 2) 2(H 2O) 2Cu(C 6H 5N 2O 2) 2Cu 2Br 2·3(H 2O)] n ( 4) as a minor phase and [Cu(C 6H 5N 2O 2) 2Cu 2Br 2·] n ( 5) as the major phase. Compound 4 adopts a two-dimensional structure, while 5 is three-dimensional. The structural classification of these Cu(I) containing coordination polymers is discussed. These new coordination polymers feature mixed-valent Cu(I)–Cu(II) frameworks and exhibit impressive thermal stability (the frameworks collapse between 236 and 246 °C). The magnetic susceptibilities for 2, 3 and 5 followed the Curie law, indicating simple paramagnetic behavior.

Dipolar dephasing between quadrupolar and spin- [formula omitted] nuclei. REDOR and TEDOR NMR experiments on VPI-5

In this work we examine the use of dipolar-dephasing magic-angle spinning NMR to study mixed pairs of quadrupolar and spin- 1 2 nuclei in solids. Dipolar connectivities are examined in both directions between the 27Al ( I=5/2) spins in the very large pore aluminophosphate VPI-5, which is considered representative of a range of inorganic framework materials. Rotational-echo double-resonance (REDOR) and transferred-echo double-resonance (TEDOR) experiments are demonstrated, as well as a two-dimensional extension of the TEDOR experiment. These experiments restore the heteronuclear dipolar coupling under MAS conditions via a train of radiofrequency pulses, thereby providing information about connectivities and distances between coupled nuclei in these inorganic solids.