Hexagonal Channels Research Articles

Mixed-Valence Iron Dumortierite Fe13.52.22+(As5+O4- x)8(OH)6 and Its Intricate Topotactic Exsolution at Mild Temperatures.

The mixed-valent iron arsenate hydroxide Fe13.52.22+(AsO4- x)8(OH)6, x = 0.25, was prepared using the reaction of iron metal with arsenate in aqueous solution and autogenous pressure. Its crystal structure reveals a dumortierite-like framework with mixed-valent Fe2+/Fe3+ in double chains creating channel walls. Remarkably, hexagonal channels consist of chains of face-sharing Fe2+O6 octahedra, 3/4th occupied, whereas AsO4 tetrahedra occupy triangular ones with a single " up" orientation according to the polar P63 mc symmetry. We have analyzed the transformation of this phase upon heating, in which several chemical processes interact, including dehydroxylation, arsenate to arsenite reduction, and oxidative exsolution of a significant part of iron (ca. 15%) found at the surface as hematite and amorphous Fe-rich surficial layer. It leaves a strongly disordered composite structure between several Fe3+-based subunits, in which ∼80% of them is ordered in a complex supercell. Because of the high degree of disorder, the crystal chemistry of the individual subunits and their plausible imbrication were considered to unravel the most plausible ideal 3D model.

Synthesis and structures of two three-dimensional hybrid materials based on vanadium polyoxoanions and macrocyclic metal complexes

The reactions of transition metal macrocyclic complexes [ML](ClO4)2 (L = 1,8-diethyl-1,3,6,8,10,13-hexaazacyclotetradecane, M=Ni, Cu) with NH4VO3 gave two coordination polymers, formulated as [NiL]3[VO3]6·0.5H2O (1) and [CuL]3[VO3]6·2H2O (2). Single-crystal X-ray diffraction analyses indicated that the central Ni(II)/Cu(II) atom achieves a distorted six-coordinate octahedral coordination geometry by the coordination of four nitrogen atoms from L, plus two oxygen atoms from [VO4] tetrahedra. Six [VO4] tetrahedra form a hexanuclear [V6O18]6− ring by sharing six μ2-oxygen atoms. The [NiL]2+ and [CuL]2+ moieties bridge the [V6O18]6− rings to form three-dimensional frameworks with one-dimensional hexagonal channels.

A stable mesoporous metal-organic framework as highly efficient sorbent of dispersive micro solid-phase extraction for the determination of polycyclic aromatic hydrocarbons by HPLC.

Owing to the large molecular sizes of polycyclic aromatic hydrocarbons, their adsorption using microporous sorbents leads to a low adsorption capacity. Here, to increase the extraction capacity and detection sensitivity of polycyclic aromatic hydrocarbons, a highly efficient dispersive micro solid-phase extraction method was developed based on a stable mesoporous metal-organic framework named Jilin University China 48. Jilin University China 48 is a super hybrid with large one-dimensional hexagonal nanotube-like channels of 24.5×27.9Å, which exhibits high potential to be an efficient sorbent of dispersive micro solid-phase extraction to adsorb polycyclic aromatic hydrocarbons. By combining with high-performance liquid chromatography, a sensitive method was developed for the determination of seven polycyclic aromatic hydrocarbons. The synthesized Jilin University China 48 exhibited excellent characteristics of stability, good morphology, large surface area, and open adsorption sites. Under the optimized extraction conditions, better extraction results were obtained than that of other methods reported previously. The proposed method exhibited high sensitivity with the limit of detections in the range of 0.021-0.13ng/mL, good linearity in the range of 0.068-50ng/mL with related coefficients of >0.9988, satisfactory precision with relative standard deviation of <4.3%, and adequate recoveries between 85.8 to 109.55% for all the target compounds.

Two d10 Metal–Organic Frameworks as Low-Temperature Luminescent Molecular Thermometers

The assemblies of a p-conjugated organic luminophore ligand (p-tr2Ph) and d10 transition metal cations produce two metal–organic frameworks (MOFs), [Zn(μ4-p-tr2Ph)(μ2-NO3)]·NO3 (1), and {[Cd2(μ4-1,4-BDC)2(μ4-p-tr2Ph)(μ2-DMF)(H2O)2]}·2H2O (2) (p-tr2Ph = 1,4-phenylene-4,4′-bis(1,2,4-triazole), DMF = N,N′-dimethylformamide, 1,4-H2BDC = 1,4-dicarboxybenzene). Compound 1 is a new three-dimensional (3D) cationic framework with left-handed helical channels constructed from a right-handed helical chain [Zn(μ2-tr)2(μ2-NO3)]n. Compound 2 possesses a 3D 3-fold interpenetrated neutral framework with one-dimensional distorted hexagonal channels in each MIL-88 type single-net. The compounds 1 and 2 both exhibit blue fluorescence. Notably, the intensity-based luminescent thermometer measurements reveal that compound 2 is extremely more linear with temperature, has finer reversibility within three cycles, and a wider temperature range than those of compound 1, indicating that compound 2 is a more desirable low-temperatur...

Direct synthesis of highly crystalline single-phase hexagonal tungsten oxide nanorods by spray pyrolysis

The metastable state hexagonal-tungsten oxide (h-WO3) has been attracting attention over the past decade because of its high reactivity that arises from the hexagonal channels in its crystal structure. Simplification of the process used to synthesize h-WO3 is an important step to facilitate the industrial applications of this material. In this study, we addressed this challenge by developing a spray pyrolysis process to synthesize highly crystalline h-WO3. The ratio of the monoclinic to the hexagonal phase was controlled by adjusting the segregation time. Single-phase h-WO3 nanorods were synthesized using a carrier gas flow rate of 1 L/min, which was equivalent to a segregation time of 18.4 s. The ability of the h-WO3 nanorods to adsorb nitrogen and carbon dioxide was evaluated to confirm the presence of hexagonal channels in the crystal structure.

Optimizing H2, D2, and C2H2 Sorption Properties by Tuning the Pore Apertures in Metal-Organic Frameworks.

By adjustment of the arm lengths of two triphenylamine-based ligands, two nearly isostructural metal-organic frameworks (MOFs), namely, the reported nanoporous FIR-29 (FIR = Fujian Institute of Research) and the new microporous FJI-Y9 (FJI = Fujian Institute), are obtained, and all exhibit honeycomb lattices of hexagonal channels with Ca-COO chains connected by tris[(4-carboxyl)phenylduryl]amine (H3TCPA) ligands and 4,4',4''-nitrilotribenzoic acid (H3NTB) ligands, respectively. Although the Brunauer-Emmett-Teller (BET) surface area (1117 m2 g-1) and pore size (8.5 Å) of FJI-Y9 are much lower than those (BET surface area of 2061 m2 g-1 and pore size of 16 Å) of the reported FIR-29 because of the shorter arm lengths of H3NTB, the activated FJI-Y9-ht shows high H2 (202.3 cm3 g-1) and D2 (221.9 cm3 g-1) uptake under 77 K and 1 bar and C2H2 uptake of 168.9 cm3 g-1 under 273 K and 1 bar, which are all at least 48% enhancement over those of FIR-29-ht. The above results indicate that small pores in MOFs are beneficial to the uptake of some special gases including H2, D2, C2H2, etc.

A Novel Magnesium Metal-Organic Framework as a Multiresponsive Luminescent Sensor for Fe(III) Ions, Pesticides, and Antibiotics with High Selectivity and Sensitivity.

Iron(III) ions play a vital role in living biological systems, while organic pollutants including pesticides and antibiotics pose a great threat to the ecological environment. Effective detection for these species is crucial for human health and environmental protection. In this work, we designed and synthesized a new amino-decorated bridging ligand H2APDA and employed it to react with the environmentally friendly Mg(II) ions to construct a novel magnesium luminescent metal-organic framework (Mg-LMOF), namely [Mg2(APDA)2(H2O)3]·5DMA·5H2O (Mg-APDA). The as-synthesized Mg-LMOF is a three-dimensional framework with one-dimensional hexagonal channels. These microporous channels are decorated with Lewis-base amino sites and uncoordinated O atoms, which facilitate the Mg-APDA to anchor and recognize various analytes. Mg-APDA can be used as a multiresponsive luminescent sensor to detect Fe(III) ions, pesticides, and antibiotics effectively. To the best of our knowledge, this work represents the first amino-decorated Mg-LMOF as an efficient fluorescent sensor for detecting metal ions, pesticides, and antibiotics simultaneously.

Lanthanide Discrimination with Hydroxyl-Decorated Flexible Metal-Organic Frameworks.

We report two new highly crystalline metal-organic frameworks (MOFs), derived from the natural amino acids serine (1) and threonine (2), featuring hexagonal channels densely decorated with hydroxyl groups belonging to the amino acid residues. Both 1 and 2 are capable of discriminating, via solid-phase extraction, a mixture of selected chloride salts of lanthanides on the basis of their size, chemical affinity, and/or the flexibility of the network. In addition, this discrimination follows a completely different trend for 1 and 2 because of the different locations of the hydroxyl groups in each compound, which is evocative of steric complementarity between the substrate and receptor. Last but not least, the crystal structures of selected adsorbates could be resolved, offering unprecedented snapshots on the capture process and enabling structural correlations with the separation mechanism.

Enclathration of Ethane, Propane, and Propylene into Urea Clathrates and Roles of Methanol on Urea Clathrate Formation.

As a guest molecule of urea clathrate, a long-chain normal alkane and its derivative with low substituents in methanol solutions have been reported. To investigate the role of methanol in the urea clathrate formation, in the present study, we used propane (C3H8), propylene (C3H6), ethane (C2H6), and methane (CH4) as guest molecules. Raman spectra and powder X-ray diffraction profiles revealed that, regardless of the existence of methanol, the C3H8, C3H6, and C2H6 molecules are enclathrated into urea clathrates with a hexagonal structure, whereas there is no urea clathrate formation enclathrating CH4. The pressurization of the urea clathrates including C2H6 and C3H8 reveals that no pressure-induced structural phase transition occurs at pressures up to 200 MPa. In spite of the guest molecule much shorter than the lattice constant of the c-axis of the hexagonal channel structure, the urea clathrates have a fairly rigid structure against the compression. Methanol as an auxiliary solution is not always necessary for the urea clathrate formation. Methanol plays a role in decreasing the activation energy of the urea clathrate formation, although it makes urea clathrate thermodynamically unstable due to the high solubility of urea in methanol.

Pure Organic Hexagonal–Channels Constructed by C–I···–O–N+ Halogen Bond and π–Hole···π Bond under Mediation of Guest

The pure organic hexagonal–channel host is first assembled by 1,4-diiodotetrafluorobenzene and 4-phenylpyridine N-oxide under mediation of linear guest molecules using robust C–I···–O–N+ halogen bond, π–hole···π bond, and weak hydrogen bonds. The guest molecules dwell in the host by parallel–offset π–π stacking and interact with host by weak C–H···π hydrogen bonds to stabilize the host–guest structure. The as-prepared host–guest cocrystals exhibit different photoluminescence colors at room temperature, bright cyan, sapphire blue, and pink, respectively, originating mainly from the guest molecules. It is expected that the synergistic host–guest assembly and its photoluminescence behavior should be significant in fabricating smart photomolecular devices in future.

Tunable mesoporosity and hydrophobicity of natural rubber/hexagonal mesoporous silica nanocomposites

Polymer/silica nanocomposites with diverse mesoporosity and hydrophobic properties have actual and potential applications in the area of catalysis, adsorption and drug delivery. The present work reports a simple but efficient approach to tune the mesostructure and hydrophobicity of natural rubber (NR)/hexagonal mesoporous silica (HMS) nanocomposites synthesized via the in situ sol-gel technique in the presence of different primary amines (C n H 2 n +1 NH 2 , n = 8, 10, 12, 14 and 16) as structural templating agents. The change in the mesostructure ordering and textural properties of the NR/HMS nanocomposites with different template sizes was similar to that for the pure silica HMS series. Powder X-ray diffraction and transmission electron microscopy analyses revealed an expansion of the hexagonal unit cell and channel wall thickness of the nanocomposites due to the incorporated rubber molecules. Using amine templates with longer alkyl chains provided NR/HMS materials with a higher NR content at 13.7–15.6 wt% but decreased the rubber phase dispersion and hydrophobic properties. X-ray photoelectron spectroscopy indicated that the amount of NR exposed at the composite's surface was 7.99–9.48 wt%, while the remaining NR was incorporated into the mesostructured silicate framework and/or entrapped in the mesopores. The hydrophobic interaction between the NR molecules and the alkyl chains of primary amine template was probably a crucial factor that determined the rubber phase dispersion, and so the hydrophobic character, in the NR/HMS nanocomposites. • A series of NR/HMS nanocomposites were synthesized via in situ sol-gel method. • Their mesoporosity and hydrophobicity varied with type of primary amine template. • Using longer amine templates enhanced the rubber content but lowered dispersion. • Using shorter amine templates gave the materials with more hydrophobic surface.

Formation of Open Framework Uranium Germanates: The Influence of Mixed Molten Flux and Charge Density Dependence in U-Silicate and U-Germanate Families.

Seven novel open-framework uranyl germanates, K2(UO2)GeO4, K6(UO2)3Ge8O22, α-Cs2(UO2)Ge2O6, β-Cs2(UO2)Ge2O6, Cs2(UO2)GeO4, and A(UO2)3(Ge2O7)2 (A = [NaK6Cl]6+, [Na2Cs6Cl2]6+), were grown from different mixed molten fluxes. The three-dimensional (3D) structure of K2(UO2)GeO4 with 8-ring channels can be built upon [UGe4] pentamer secondary building units (SBUs). The 3D framework of K6(UO2)3Ge8O22 with trapezoid (Ge8O22)12- clusters consists of two types of [UGe4] pentamers. The 3D framework of α-Cs2(UO2)Ge2O6 with 10-ring channels, crystallizing in the P21/ n space group, is constructed by [UGe4] pentamers. The structure of β-Cs2(UO2)Ge2O6 contains achter (eight) single germanate chains and is composed of [UGe6] heptamers and [UGe4] pentamers. The structure of Cs2(UO2)GeO4 with hexagonal 10-ring channels is composed of [U3Ge4] heptamers and twisting five-fold GeO4 tetrahedra in four-membered Ge4O12 rings occur. 3D frameworks of NaK6Cl(UO2)3(Ge2O7)2 (space group Pnnm) and Na2Cs6Cl2(UO2)3(Ge2O7)2 ( P21/ c) can be constructed from the same SBUs [UGe4] pentamers. Thermal stability of salt-inclusions was studied by TG and PXRD analysis. Analysis of charge density for the U-Si-O system indicates that the polymerization of silicate units reduces the cross-links of the 3D frameworks. The concept of SBUs combined with the cutting and gluing strategy was applied to understand and analyze the distinct 8-, 10-, 12-, and 14- membered channels for the uranyl germanate family. The charge density of all known 3D U-Si/Ge-O frameworks has been investigated, which shows strong correlations with chemical composition of corresponding phases. The increase of Si/O (Ge/O) ratios in silicate units results in the decrease of negative charge density. Moreover, the charge density increases with decreasing countercation size within the same Si/O ratio. The correlations can be used to predict inclusion phase formation within U-Si/Ge-O families. Raman spectra of the studied uranyl germanates were measured, and bands were assigned on the basis of structural features.

Ion Intercalation into Vanadium Sulfides for Battery Applications

Global battery manufacturing capacity will more than double by 2021 to about 280,000 megawatt-hours.1 Rechargeable batteries make up a significant fraction of battery manufacturing. A rechargeable battery cell is made up of two electrodes, the anode and the cathode, separated by an electrolyte. For solid electrodes, an electrolyte-permeable separator separates them. Chemical reactions at the anode and the cathode produces two components; ionic and electronic. The electrolyte conducts the movement of ions inside the cell while forcing electrons to pass through outside of the cell. Current collectors at the anode and the cathode deliver electric current to and from the external circuit. During discharge, electrons and ions flow from the anode to the cathode. On charge, an applied electric field forces the electrons and ion to flow back from the cathode to the anode.2 Lithium-ion technology has dominated the rechargeable battery industry because of their high energy density, and portability. High cost, safety issues, and charge storage capacity limit lithium-ion technology. These problems have sparked new interest in rechargeable batteries with multivalent ions like magnesium ion (Mg-ion). Magnesium is divalent, cheaper than lithium, easy to handle, and environmentally friendly. It has 1.85 times the theoretical volumetric capacity of lithium.3 Passivation and choice of cathode materials have hindered Mg-ion technology. Passivation produces a surface thin film on the metal anode that prevents reversibility of magnesium ions. Electrolytes from magnesium organo-halo-aluminate complexes in ether solvents have significantly reduced passivation problems.4 The choice of cathode material remains elusive. Theoretical predictions have shown high magnesium ion mobility in six-coordination, spinel close-packed frameworks.5 Mg-ion has been reported to favor octahedral environment in oxides and sulfides.6 This project focuses on investigating vanadium sulfides compounds, AxV5S8, AxV6S8, and V5S8 as candidate cathode materials for Mg-ion battery. A is an alkali metal, or monovalent cation and x = 0 – 0.8. AxV6S8 has a hexagonal unit cell formed from a distorted VS6 octahedral sharing faces and edges, with large hexagonal channels capable of intercalating ions.7 AxV5S8 has a monoclinic structure. It has a three-dimensional framework made from slightly distorted VS6 octahedral sharing edges and faces, with rectangular tunnels prime for ion insertion.8 Both AxV5S8 and AxV6S8 have short V-V zigzag chains that make both metallically conductive.5,6 V5S8 has a monoclinic structure with every three-quarter of metal atom position vacant in every layer of the NiAs structure.9 Stoichiometry mixtures of vanadium sulfide compounds are synthesized in evacuated sealed quartz tubes. The products are handled and analyzed under argon. Samples of AxV6S8, AxV5S8, and V5S8 are characterized using powder XRD. Electrochemical properties of the vanadium sulfide compounds are studied using cyclic voltammetry and chronopotentiometry. Cell assembly consists of lithium metal anode, 80 % vanadium sulfide compound cathode, 1 M LiClO4 in 1:1 EC:DEC electrolyte, glass frit, Kynar, and graphite. XRD pattern for as prepared KxV5S8 matched with a known KxV5S8 pattern in the International Center for Diffraction Data database (ICDD). KxV6S8 XRD pattern showed KxV5S8 phase peaks when matched with the ICDD database, indicating phase impurity. Potassium is not a big enough metal to make the AxV6S8 framework. The XRD patterns of RbxV5S8, RbxV6S8, and V5S8 matched with ICDD database patterns for each compound without showing any phase impurities. Cyclic voltammetry and chronopotentiometry data with a lithium anode and the lithium-ion electrolyte indicate that KxV5S8 and RbxV5S8 are not electrochemically active. V5S8 is electrochemically active. It shows significant oxidation and reduction peaks during cyclic voltammetry with a lithium anode. In the future, RbxV6S8 will be investigated for electrochemical activity. Intercalation reactions of magnesium ion will be investigated in the electrochemically active compounds of vanadium sulfide compounds for battery applications. Figure 1

Frictional and Heat Transfer Characteristics of Flow in Triangle and Hexagon Channels of Wall-Flow Monoliths

In the 1D modeling of flow and heat/mass transfer of wall flow monoliths (WFMs), it is common to use a friction factor and Nusselt number generated from an idealized 2D/3D solution. The results are usually expressed as functions of wall Reynolds number and Peclet number, and they have been derived for circular tubes and parallel plates with porous walls decades ago. Recently, the 3D solution has been generated for fully developed laminar flow in square channels with porous walls and uniform wall velocity, and the general functions for friction factor and Nusselt number were derived for 1D modeling. In this work, we extend the study to the 3D geometry of additional regular polygons, particularly hexagons and triangles, since they are also used for wall flow monoliths to filter exhaust emissions. In order to extend the life span of the monolith, asymmetric channel designs with different inlet-to-outlet channel ratio or different sizes have become an important approach. The main idea is to increase the soot or ash capacity in the inlet channels. For the hexagonal channel design, two inlet channels per outlet channel are common. Due to the different inlet/outlet channel ratio, the flow and heat transfer characteristics are significantly different compared to traditional design with the same inlet/outlet channel ratio. The difference between the asymmetric design and symmetric design is studied, and the implication for 1D modeling is discussed.

Crystal chemistry of K-rich nepheline in nephelinite from Hamada, Shimane Prefecture, Japan

AbstractK-rich nepheline with a structural formula of A2B6T14T24T34T44O32 (Z = 1) within melilite–olivine nephelinite from Hamada, Shimane Prefecture, Japan, was investigated to clarify its crystal structure and to determine cation distributions in the A and B structural positions of structural channels and tetrahedral T1–T4 sites. The chemical formula of a single-crystal sample was (Na5.437K2.248Mg0.034Ca0.031)Σ7.750(Si8.332Al7.445Fe3+0.158Ti0.009Cr0.005)Σ15.949O32, which results in 65.2, 27.8, 2.1, 3.2 and 1.6 mol.% NaAlSiO4, KAlSiO4, NaFe3+SiO4, □Si2O4 and □0.5(Ca,Mg)0.5AlSiO4 end-member components, respectively, where □ is a vacancy. X-ray diffraction data of a single crystal with dimensions of 0.28 mm × 0.15 mm × 0.05 mm measured at 296 K indicate the space group P63. In the structural refinement, the R1 factor was reduced to 3.69% by taking twinning by merohedry into the refinement. The refinement accounted for 77.7% of the absolute structure and 22.3% of the a and b axes reversed absolute structure. The atomic populations determined in the A and B positions were 1.834 K + 0.166 □ and 5.705 Na + 0.198 K + 0.031 Ca + 0.034 Mg, respectively, implying the substitution of K for Na in the B position. The a and c dimensions are a = 10.0270(3) and c = 8.4027(3) Å. The average &amp;lt;A–O&amp;gt; and &amp;lt;B–O&amp;gt; distances are 3.009 and 2.65 Å, respectively. The substitution of K for Na in the B channel results in increased volume and bond-length distortion of the BO8 polyhedra, which then reduces distortion of the AO9 polyhedra. The average T–O distances indicate that the T1 and T4 sites are essentially filled with Al, whereas the T2 and T3 are filled with Si. Despite the deviation of the O1 oxygen from the triad axis and the combination of K+ ions and vacancies in the hexagonal channels, an incommensurate structure was not observed in the X-ray diffraction data or using the electron diffraction technique.

Amino functionalized chiral mesoporous silica nanoparticles for improved loading and release of poorly water-soluble drug

In the present paper, chiral mesoporous silica nano-cocoon (A-CMSN) functionalized with amino group was synthesized, and its loading and release of indomethacin (IMC), a poorly soluble drug, was studied. Due to the use of chiral anionic surfactants as a template, A-CMSN possessed 2D hexagonal nano-cocoon morphology with curled channels on its surface, which was quite different from another 2D hexagonal mesoporous silica nanoparticles (MCM-41) with straightway channels. After being loaded into the two silica carriers by hydrogen bond, crystalline IMC converted to amorphous form, leading to the improved drug dissolution. And IMC loading capacity of A-CMSN was higher than MCM-41 because curled loading process originating from curvature chiral channels can hold more drug molecules. Compared with IMC, IMC loaded A-CMSN presented obviously fast release throughout the in vitro release experiment, while IMC loaded MCM-41 released faster than IMC at the initial 5 h then showed controlled slow release afterwards, which was closely related to the mesoporous silica nanoparticles and different channel mesostructures of these two carriers. A-CMSN possessed nano-cocoon morphology with curled 2D hexagonal channel and its channel length was shorter than MCM-41, therefore IMC molecules can easily get rid of the constraint of A-CMSN then to be surrounded by dissolution medium.

3D printing complex lattice structures for permeable liver phantom fabrication

Liver cancer is currently the third deadliest cancer in the world, affecting over 700,000 people per year. To improve early detection of tumours, perfusion testing is used for imaging of blood flow in the liver. Creating a phantom to accurately mimic the liver in imaging techniques such as Dynamic Contrast-enhanced (DCE) computed tomography (CT) will improve testing and calibration of different imaging protocols and pharmacokinetic perfusion models. In current literature, there lacks a permeable, easily producible and reusable liver phantom for dynamic contrast-enhanced CT perfusion testing. This study details the production of phantoms with controllable permeability for standardization in hepatic perfusion using commercially available 3D printing methods. Phantoms with hexagonal channels were designed in nTopology Element and printed in materials with a density of 0.9–1.5 g/cm3. Polylactic acid was selected for fused deposition modelling (FDM), while proprietary resins were used for an inkjet printing process called MultiJet Printing (MJP). Permeability tests were performed on samples to observe flow rates obeying Darcy's Law. Scanning electron microscopy (SEM) was used to analyze pore size in FDM and MJP samples, while micro-CT scans were performed to analyze pore interconnectivity. The collected permeability data exceeds reported literature values of 0.0167 mL s−1 cm2 and approach the desired range of 0.15–0.3 mL s−1 cm2. Micro-CT scans show obstructions from the MJP printing process. SEM images were analyzed in Fiji and showed varying results for FDM printing. Future work will involve reducing pore size while maintaining high permeability. Using 3D printing in phantom development will help create adaptable, reliable and permeable phantoms for diagnostic imaging.

A luminescent metal-organic framework with helical SBUs for highly effective detection of Fe3+ ions

A luminescent 3D metal-organic framework, [CdL(H2O)]·1DMF·1.5H2O (1, L = 1-(4-carboxyphenyl)-5-methyl-2,5-dihydro-1H-pyrazole-3-carboxylic acid, DMF = N,N-dimethylformamide), has been successfully synthesized and structurally characterized. The overall structure of 1 contains hexagonal channels and is constructed by helical SBUs with etb topology. Interestingly, compound 1 exhibits good fluorescence intensity in DMF and can be quenched by trace amounts of Fe3+ ions. The Ksv values of compound 1 towards Fe3+can reach up to 3.5 × 104 which surpass some MOFs materials. More importantly, compound 1 is also a recyclable luminescent sensor which can be potentially applied in detecting Fe3+.

Exceptionally Stable and 20-Connected Lanthanide Metal–Organic Frameworks for Selective CO2 Capture and Conversion at Atmospheric Pressure

Highly thermal and chemically stable, 20-connected lanthanide metal–organic frameworks (MOFs) [{Ln(BTB)(H2O)}·H2O]n (where Ln = Sm (MOF1)/Gd (MOF2), BTB = 1,3,5-tris (4-carboxy phenyl) benzene) have been synthesized solvothermally and characterized by single-crystal X-ray diffraction analysis and other physicochemical methods. MOF1 and 2 are isostructural and feature three-dimensional honeycomb-like structure with large one-dimensional hexagonal channels of dimension ∼10.20 × 10.11 A2. Gas uptake studies of the samples revealed selective adsorption properties of MOF1 for CO2 over other (N2, Ar, and H2) gases. The activated samples of the MOF1/2 act as efficient recyclable catalysts for heterogeneous cycloaddition of CO2 with styrene oxide, resulting in cyclic carbonate with high yield and selectivity. Interestingly, the pore size-dependent catalytic conversion of epoxides has been observed, suggesting the potential utility of MOF1 as a promising heterogeneous catalyst for cycloaddition of carbon dioxide. ...

Isostructural lanthanide metal-organic frameworks comprised of left-handed helical chains: Synthesis, structure and luminescent properties

Six isostructural three-dimensional (3D) lanthanide metal-organic frameworks (Ln-MOFs), [Ln(μ2-OH)(PDC)(H2O)2]·DMF (Ln=Pr (1), Nd (2), Eu (3), Tb (4), Ho (5), and Yb (6), H2PDC=pyridine-3,5-dicarboxylic acid), have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal gravimetric analysis. The framework contains unusual Ln-carboxylate/μ2-OH left-handed helical chains, which are extended by PDC2− linkers to form 3D networks with 1D hexagonal channel. The lanthanide contraction effect induces the decreases of average Ln- distances from Pr to Yb. Due to the efficient sensitization of PDC2− ligand, complexes 2 and 6 display strong characteristic luminescence in the near-infrared (NIR) region, respectively. Moreover, the luminescent properties of complexes 3 and 4 are also studied in the solid state at room temperature.