Preparation of Ferrocene-Based Coordination Polymer Microspheres and Their Application in Hydrogen Storage

In this article, a functional ferrocene-based metalloligand has been synthesized and used as the building block to assemble novel coordination polymer microspheres. Specifically, this metalloligand was coordinated with two different types of metal ions (Co²⁺ and Mn²⁺) to fabricate two different but isostructural microspheres under solvothermal conditions. To deepen our understanding of the formation process of the coordination polymer microspheres, a growth mechanism has been proposed based on the morphology change of these spheres throughout the whole reaction process. Furthermore, the prepared multi disperse microspheres, in the form of hollow spheres with high thermostability, can be applied to store hydrogen for their promising hydrogen uptake capacity (1.84wt% for CPM-1 and 1.00 wt% for CPM-2 at 163 K under 5 MPa). Moreover, the different adsorption enthalpies of these two materials that relevant to the varied hydrogen uptake capacity have been calculated, compared and explained.     

Synthesis,Crystal Structures,Luminescence, Biological and Catalytic Properties of Two d10 Metal-Organic Coordination Polymers Constructed from Mixed Ligands

Two d¹⁰ metal-organic coordination polymers, [Cd₂(4-cpa)₄(bmip)₂]_n (1) and [Zn(4-cpa)₂(4,4′-bpy)]_n (2), [4-cpa = 4-chlorophenylacetate, bmip = 1,3-bis(2-methylimidazoly)propane, 4,4′-bpy = 4,4′-bipyridine], were hydrothermally synthesized and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies indicated that both 1 and 2 display analogous wave-like infinite chain structures. The two coordination polymers are further extended into 3D supramolecular structures through π···π stacking interactions and C–H···O hydrogen bonds for 1 and π···π stacking interactions, C–H···π stacking interactions and C–H···O hydrogen bonds for 2. Both 1 and 2 emit the intense blue luminescence at room temperature. The 4-Hcpa ligand and complexes 1 and 2 have been screened for their herbicidal activities against Brassica napus L. and Echinochloa crusgalli L. The results are compared with the activity of quizalofop-P-ethyl. Both compounds exhibit high catalytic properties on degradation of methyl orange in Fenton-like process.     

Syntheses, Crystal Structures, Thermal Stabilities and Luminescent Properties of Two Pillared Layered Alkaline–Earth Coordination Polymers

Two new three-dimensional pillared layered coordination polymers, [M(2,5-PDC)H₂O]_n [M(II) = Sr(1), Ba (2)] were synthesized under hydrothermal conditions using alkaline–earth metal centers strontium and barium with 2,5-pyridinedicarboxylic acid as the organic ligand. The structures of two compounds have been determined by single-crystal X-ray diffraction analyses and further characterized by IR spectrum, elemental analyses, powder X-ray diffraction, and thermogravimetric analyses. The compounds are isostructural, confirmed by their powder XRD measurements. They feature a pillared layered framework structures. Within the layer, the dinuclear [M₂O₂] units through the bridge of the coordination water molecule are found, which are connected by carboxylate groups along the a- and b-axis, respectively. The layers are further pillared by the pyridyl groups of the 2,5-PDC^2? ligands. Furthermore, the luminescent properties of two compounds have also been investigated in the solid state.     

Preparation, Crystal Structures and Photoluminescence of Two New Zinc Complexes Based on 1H-Imidazo[4,5-f][1,10]-phenanthroline and Auxiliary Ligands

Two new coordination polymers [Zn(ip)(2,5-tda)(H₂O)₂] _n (1) and [Zn₂(ip)₂(5-npa)₂] _n (2) (2,5-tda = thiophene-2,5-dicarboxylic acid, ip = 1H-imidazo[4,5-f][1,10]-phenanthroline and 5-npa = 5-Nitroisophthalic acid) were synthesized and characterized by IR, elemental analysis, PXRD and X-ray diffraction. Single-crystal X-ray analyses revealed that 1 and 2 demonstrate a 1D chain structure. Complex 1 was bridged by 2,5-tda ligands in a μ₁ ? η¹:η⁰/μ₁ ? η¹:η⁰ coordination mode, and further extended into a 2D supramolecular structure by hydrogen bonding and π···π interactions. In 2, the 5-npa ligand acts as a bridging moeity, exhibiting μ₁ ? η¹:η¹/μ₁ ? η¹:η⁰ and μ₁ ? η¹:η⁰/μ₁ ? η¹:η⁰ coordination modes to link metal ions to form a 1D chain. The chains are further connected via hydrogen bonding interactions into a 2D supramolecular structure. The luminescent properties for 1 and 2 were investigated in the solid state at room temperature.     

Synthesis and characterization of monodisperse hollow SnO<Subscript>2</Subscript> microspheres and their enhanced sensing properties to ethanol

The monodisperse hollow SnO₂ (H-SnO₂) microspheres were successfully synthesized by the ion exchange method using sulfonated PS microspheres as a template. The structure and morphology were characterized by X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy, which confirms the hollow structure of the products. The H-SnO₂ microspheres are composed of numerous SnO₂ nanoparticles with a shell thickness of about 13 nm. The monodisperse H-SnO₂ microspheres have a high specific surface area of 55.54 m²/g, which improves the gas sensing properties toward ethanol. Gas-sensing measurement results indicate that H-SnO₂ microspheres exhibit an excellent sensitivity (103.1) toward 200 ppm ethanol at 260 °C, which is much higher than that (65.8) of SnO₂ nanoparticles.     

Syntheses and Characterization of Three Coordination Polymers of Zinc(II) and Cadmium(II) with Dicarboxylates and Bis(thiabendazole) Ligands

Three d ¹⁰ coordination polymers formulated as [Zn(L1)₂(mip)] _n (1), [Zn(L1)(2,6-ndc)] _n (2) and [Cd(L2)_0.5(bpdc)] _n (3) (L1 = 1,1′-(1,3-propanediyl)bis(thiabendazole), L2 = 1,1′-(1,6-hexanediyl)bis(thiabendazole), H₂mip = 5-methylisophthalic acid, 2,6-H₂ndc = 2,6-naphthalenedicarboxylic acid, H₂bpdc = 4,4′-biphenyldicarboxylic acid) were hydrothermally synthesized. Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction analysis, and single crystal X-ray diffraction. Complexes 1 and 2 present different chain structures, both of them are extended into 2D supramolecular architectures via C–H···O hydrogen bonds, while 3 is a three-fold interpenetrating three-dimensional framework with binodal 4,4-connected mog topology. The thermal stability, UV–visible spectroscopy and luminescence properties of complexes 1–3 were also examined. Furthermore, complex 3 exhibits relatively positive catalytic activity towards the degradation of methyl orange in a Fenton-like process.     

Coordination Behaviors and Supramolecular Interactions of 2-(2′-Pyridyl) Imidazoline: Crystal Structure of Its Two Cu(II) Complexes

Two new copper coordination complexes, [Cu(PI)(OX)(H₂O)]·H₂O (1) and [Cu(PI)(fum)(H₂O)]·H₂O (2) [PI = 2-(2′-pyridyl) imidazoline, OX^2? = dianion of oxalic acid and fum^2? = dianion of fumaric acid], were synthesized by interface diffusion method based on Cu(II) ions, PI ligands and aliphatic dicarboxylic acids. Complex 1 is a mononuclear complex which spreads into a 3D (4,9)-connected supramolecular network via hydrogen bond interactions, while complex 2 features a 1D zigzag chain with two different orientations. These two compounds are characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, infrared spectra, and thermogravimetric analyses.     

Inter-polymer complex microspheres of chitosan and cellulose acetate phthalate for oral delivery of 5-fluorouracil

Inter-polymer complexes (IPCs) of chitosan (CS) and cellulose acetate phthalate (CAP) have been prepared to develop spherical microspheres by a novel emulsion-solvent evaporation technique. The microspheres were used for the oral delivery of 5-fluorouracil (5-FU), an antimetabolite and antineoplastic agent, whose release time was extended up to 12 h. Formulations were prepared by varying the concentrations of CS, CAP and 5-FU. FTIR confirmed the formation of IPC, indicating no chemical interactions of 5-FU with the polymer matrix. Scanning electron microscopy suggested spherical shape of the microspheres with smooth surfaces. Average particle size measured by optical microscopy varied between 2.7 and 5.5 μm. Differential scanning calorimetry showed amorphous dispersion of 5-FU particles into the IPC matrix. Encapsulation efficiency as estimated by UV was dependent on polymer composition with the highest value of 96 %. Water uptake by the IPC microspheres was higher at higher concentration of CS in the matrix. In vitro drug release performed in pH 1.2 and pH 7.4 buffer media showed a dependence on compositions of CS, CAP and drug loading. Molar mass between cross-links (M _c) and cross-link density (d _x ) values of the polymer matrix calculated from swelling data indicated the formation of a dense matrix between CS and CAP; the matrix was able to control the release of 5-FU. The in vitro release data have been fitted to empirical equations to understand the nature of drug release mechanism.     

Performance of Low Cost Ceramic Microfiltration Membranes for the Treatment of Oil-in-water Emulsions

Using the uniaxial compaction method, ceramic disk type microfiltration membranes were fabricated using mixtures of clays to yield membranes M₁, M₂, and M₃. These were obtained with distinct compositions of raw materials at a sintering temperature of 900°C. Membrane characterization was conducted using thermogravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD), and scanning electron microscope analysis (SEM). Morphological characterization of these membranes includes the evaluation of average porosity, pore size, mechanical stability, chemical stability, and hydraulic permeance. With varying composition of the raw materials, it is observed that the average porosity and pore size of the membrane varied between 23–30% and 0.45 to 1.30 µm. For all membranes, the flexural strength varied within the range of 10-34 MPa. Chemical stability tests indicate that the membranes are stable in both acidic and basic media. The hydraulic permeance of M₁, M₂, and M₃ membranes is about 3.97 × 10^?6, 2.34 × 10^?6, and 0.37 × 10^?6 m³/m² s kPa, respectively. Further, the performance of these membranes was studied for the microfiltration of synthetic oily wastewater emulsions. Amongst all membranes, membrane, M₂ performance is satisfactory as it provides oil rejection of 96%, with high permeate flux of 0.65 × 10^?4 m³/m² s at a lower transmembrane pressure differential of 69 kPa for the oil concentration of 200 mg/L.     

Synthesis,Characterization, Crystal Structures and Thermal and Fluorescence Studies of Dinuclear and Polymeric Silver(I) Complexes of 5,5-Diethylbarbiturate with 2,5-Dimethylpyrazine and Piperazine Involving Ag–Ag Interactions

Two silver(I) complexes, [Ag(dmpyz)₂][Ag(barb)₂] (1) and {[Ag(ppz)][Ag(barb)₂]·H₂O} _n (2) (barb = 5,5-diethylbarbiturate, dmpyz = 2,5-dimethylpyrazine and ppz = piperazine), have been synthesized and characterized by elemental analyses, IR, thermal analysis (TG-DTA) and single-crystal X-ray diffraction. Complex 1 consists of [Ag(dmpyz)₂]⁺ and [Ag(barb)₂]^? ions in which the silver(I) ions are linearly coordinated by two dmpyz or two barb ligands. These two ions are connected by strong Ag–Ag interactions (Ag–Ag = 2.896 (1) Å). Complex 2 is a 1D coordination polymer in which the silver(I) ions are bridged by the ppz ligands in a linear fashion, leading to a zigzag chain of [Ag(ppz)] _n ⁺ , which interacts with the [Ag(barb)₂]^? units by Ag–Ag interactions of 3.183 (1) Å. The 1D chains are further assembled to form 3D networks by strong N–H···O and OW–H···O hydrogen bonds. IR spectra and TG-DTA data are in agreement with the crystal structures. The fluorescent properties of 1 were also evaluated.     

1D Hydrogen-Bonded Polymers Assembled by Tetraaza Macrocyclic Metal(II) Complexes and Inorganic Salts

The self-assembly of [M(L)]Cl₂·2H₂O (M = Ni²⁺ and Cu²⁺, L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) with sodium 1,2,4-benzenetricarboxylate (Na₃btcb) and KNO₃ generates the 1D hydrogen-bonded polymers with formulas [Ni(L)(H₂btcb^?)₂] (1) and [Cu(L)(NO₃)₂] (2). These polymer complexes have been characterized by X-ray crystallography, spectroscopy and cyclic voltammetry. The crystal structure of 1 shows a distorted octahedral coordination geometry around the nickel(II) ion, with the four secondary amines of the macrocycle and two carboxylate oxygen atoms of the H₂btcb^? ligand in the trans position. In 2, the coordination environment around the central copper(II) ion reveals an axially elongated octahedron with four Cu–N bonds and two oxygen atoms of the nitrate ligand in the trans position. The cyclic voltammograms of the complexes undergo two one-electron waves corresponding to M^II/M^III and M^II/M^I processes. The electronic spectra and electrochemical behavior of the complexes are significantly affected by the nature of the axial ligands.     

Degradability and antigen-release characteristics of polyester microspheres prepared from polymer blends

Biodegradable microspheres were prepared to function as a depot system for the controlled release of a model protein antigen bovine serum albumin (BSA). As an approach to achieve its controlled release, microspheres were fabricated blending a high-molecular-weight poly-d,l-lactide-co-glycolide (M_w = 61,000) with a low-molecular-weight poly-d,l-lactic acid (M_w = 2000, PLA2000). The effects of PLA2000 on microsphere degradability and release characteristics of BSA from microspheres were investigated. On the basis of the pH change in microsphere suspensions and water uptake of microspheres, the kinetics of microsphere degradation was derived to describe the rate of formation of hydrogen ions due to hydrolysis of ester linkages of polymers. It substantiated that PLA2000-containing microspheres were subject to controlled degradation that was necessary to achieve continuous release profiles of the antigen. Immunization of rabbits by subcutaneous injection of BSA-containing microspheres enhanced the antigenicity of BSA, and significantly increased the duration of humoral immune responses. © 1995 John Wiley & Sons, Inc.     

Two Tartrate-Pillared Coordination Polymers: Hydrothermal Preparation, Crystal Structures, Spectroscopic and Thermal Analyses of {[M2(μ-C4H4O6)2(H2O)] · 3H2O}∞ (M = Mn, Cd)

Two novel three-dimensional coordination polymers, formulated as {[M₂(μ-C₄H₄O₆)₂(H₂O)] · 3H₂O}_∞ (M = Mn for 1 and Cd for 2), have been synthesized under hydrothermal reaction condition. Both complexes were characterized by elemental analysis and IR spectroscopy. Their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA-DTA methods. Compound 1 crystallizes in the monoclinic space group, P2₁, while compound 2 crystallizes the orthorhombic space group, P2₁2₁2₁. The structures are self-assembled from bifunctional tartrate and water molecules. Tartrate ligands in 1 and 2 contribute to both covalent and hydrogen bonds. Polymeric chains of 1 and 2 are composed of M(II) ions bridged by tartrate ions in O,O′ fashion. The asymmetric units of coordination polymers contain two metal centers having different coordination environments.     

Synthesis,Structure and Fluorescence Spectra Study of a Supramolecular Zinc(II) Complex

A new structural supramolecular zinc(II) complex (1), [Zn(H₂O)₆]²⁺[Zn(4,4′-bipy)(SO₄)₂(H₂O)₂]^2?[Zn(4,4′-bipy)(SO₄)(H₂O)₃] is synthesized in mixed solvent system at room temperature. The complex was characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Structural analyses reveal that the complex is crystallized in the triclinic system with P1 space group. Cell parameters: a = 7.3145 (15) Å, b = 11.194 (2) Å, c = 11.442 (2) Å, α = 72.48 (3)°, β = 73.78 (3)°, γ = 83.39 (3)°, V = 857.3 (3) ų. Zn atoms (Zn1, Zn2 and Zn3) are all six-coordinated, however, the coordination environments of them are different. Owning to the abundant intro- and inter- hydrogen bonding interactions, the adjacent molecular units were connected to form a 2D supramolecular chain, and the two adjacent chains were furthermore linked to form a 3D supermolecular network structure via the hydrogen bonds. In addition, it is found that the complex has potential applications as fluorescent-emitting materials due to the strong fluorescence.     

Facile fabrication of porous hollow CeO2 microspheres using polystyrene spheres as templates

Porous hollow CeO₂ microspheres were fabricated using negative-charged PS microspheres as templates by a facile method. The hollow CeO₂ microspheres were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and N₂ adsorption?Cdesorption. The results showed that the as-synthesized hollow CeO₂ microspheres are well monodisperse and uniform in size. The porous shells of hollow microspheres are relatively rough and composed of tiny nanoparticles. The external diameter, internal diameter, and shell thickness of hollow CeO₂ microspheres are about 190, 160, and 15?nm, respectively. A possible mechanism for the formation of hollow CeO₂ spheres was also discussed.     

Synthesis,Characterization, Crystal Structure and Antimicrobial Evaluation of a Novel –M–X–M–X– Type Infinite Chain 1D Cu(II) Complex with Eflornithine Hydrochloride Hydrate as Ligand

A novel –M–X–M–X– type infinite chain 1D copper(II) complex of Eflornithine, Dichloro-[2-amino-5-ammonio-2-(difluoromethyl)pentanoate]copper(II) hydrate, [Cu(C₆H₁₂F₂N₂O₂)Cl₂]·H₂O 1 has been synthesized and characterized by elemental analysis, spectroscopic techniques (UV/Vis and FT-IR), TGA and X-ray diffraction. Single-crystal X-ray diffraction analysis of the complex 1 showed the structure to be monoclinic with space group Cc, a = 13.1295(15) Å, b = 12.1859(14) Å, c = 8.1927(9) Å, β = 118.359(3) Å, V = 1153.5(2) Å³, Z = 4. The complex exhibits a quadratic planar coordination of the Cu-atom. The Cu(II) centre is coordinated by two chloride atoms, an oxygen atom of the carboxyl- and a nitrogen atom of the amino-group, respectively, forming a quadratic planar geometry. The terminal amino group of the ligand is protonated to form NH₃ ⁺ while the carboxylic moiety is deprotonated to form Zwitterionic eflornithine ligand, with the coordination of the metal at the nitrogen atom of the second amino group. The compound has –M–X–M–X– infinite 1D chain polymeric structure. Two neigbouring Cu(EFL)Cl chain units are bridged by an Cl^? ion, forming a –Cu–Cl–Cu–Cl– linear chain structure along C-axis. The antibacterial activities of the complex on Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) were investigated and found to be active at higher concentration than the parent ligand.     

Synthesis, Crystal Structure and Antitumor Activity of Ca(II) Coordination Polymer Based on 1,5-Naphthalenedisulfonate

A novel Ca(II) coordination polymer, [CaL(H₂O)₂] _n (L = 1,5-naphthalenedisulfonate), was synthesized by reaction of calcium perchlorate with 1,5-naphthalenedisulfonic acid sodium in CH₃CH₂OH/H₂O. It was characterized by elemental analysis, IR, ¹HNMR and thermal analysis. X-ray crystallographic reveals that the Ca(II) coordination polymer belongs to triclinic system, with space group P-1. The geometry of the Ca(II) ion is a distorted CaO₆ octahedron coordination environment, arising from its coordination by two water molecules, and four oxygen atoms from two l ligands. The Ca(II) ions are linked through the O atoms of 1,5-naphthalenedisulfonate ligands to form 1D chain structure. And then a 2D layered structure is constructed by hydrogen bonds and π–π stacking. The antitumor activity of 1,5-naphthalenedisulfonic acid sodium ligand and its Ca(II) coordination polymer against human hepatoma smmc-7721 cell line and human lung adenocarcinoma A549 cell line have been investigated.     

Effect of Calcination Temperature of Kaolin Microspheres on the In situ Synthesis of ZSM-5

ZSM-5 zeolite has been successfully synthesized in-situ on calcined kaolin microspheres by the hydrothermal method using n-butylamine as a template. The supported ZSM-5 was characterized by X-ray diffraction and scanning electron microscopy. The effect of calcination temperature of kaolin microspheres on the in-situ synthesis of ZSM-5 was investigated. The influence of the pretreatment temperature on the properties of kaolin microspheres including phase transformation, amounts of active SiO₂ and Al₂O₃, and pore structures, was studied using fourier transform infrared (FT-IR), nitrogen adsorption and chemical analysis. The results showed that when the calcination temperature increased from 300 to 900 °C, the amount of active SiO₂ in the kaolin microspheres increased slightly and the amount of active Al₂O₃ initially increased rapidly and then decreased steadily. The surface area and pore volume of the kaolin calcined at both low and high temperatures was less than those of kaolin calcined at a medium temperature. The property changes of kaolin caused the relative crystallinity of in situ synthesized ZSM-5 to vary.     

Microporous coordination polymer with secondary amine functional groups for CO<Subscript>2</Subscript> uptake and selectivity

The CO₂ capturing and sequestration are of importance in environmental science. A new type of microporous coordination polymer (Ni/PAPy) with secondary amine groups has been successfully prepared. Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO₂ molecules, the CO₂ uptake capacity of the microporous coordination polymer reaches up to 4.82 mmol g^?1 (1.0 bar, 273 K) with the high selectivities (CO₂/N₂?=?83, CO₂/CH₄?=?16), making the Ni/PAPy a promising microporous material for application of CO₂ uptake and separation. For comparison, the microporous coordination polymer without secondary amine groups (Ni/PPy) is also prepared.

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Graphical Abstract Taking advantage of the synergistic effect of metal-electrostatic and hydrogen bonding interactions between the Ni/PAPy network and CO₂ molecules, the Ni/PAPy can be considered as a promising microporous material for application of CO₂ uptake and separation.

     

Synthesis and Characterization of Perovskite-Type Oxides La1−xMxCoO3 (M = Ce,Sr) for the Selective CO Oxidation (SELOX)

Perovskite-type oxides La_1?xM_xCoO₃ (M = Ce, Sr) were prepared by citrate method, characterized and evaluated in the selective CO oxidation (SELOX-CO). The insertion of low Cerium or Strontium content generated solids with a single phase related LaCoO₃ perovskite. For higher contents we observed segregation of CeO₂ and SrCO₃. The iso-structural substitution favors the formation of vacancies. The SELOX-CO showed 100 % CO conversion at 200 °C. Higher temperatures favored hydrogen oxidation and methanation.