An unprecedented ten-connected 3D metal–organic framework based on hexanuclear cobalt(II) cluster building blocks

A 3D metal–organic framework (MOF), [Co₃(μ₃-OH)(μ₂-H₂O)(BPT)(HBPT)(DMF)₂]·(DMF)(H₂O) (1) (DMF = N, N′-dimethylformamide) has been synthesized by self-assembly of cobalt(II) oxide and biphenyl-3, 4′, 5-tricarboxylate (H₃BPT) under solvothermal reaction. Compound 1 displays unique (2,3,10)-connected trinodal connected topology. Besides, 1 represents a rare example of MOF possessing free carboxylic acids. In addition, the magnetic property of the compound is investigated.     

Bio-inspired composite films with integrative properties based on the self-assembly of gellan gum–graphene oxide crosslinked nanohybrid building blocks

Mimicking natural structures to synthesize novel structural materials is attracting considerable attention, but progress in practical applications remains slow. Natural composites achieve excellent balance between strength and toughness from the “brick-and-mortar” arrangement of organic and inorganic layers, accompanied with various toughening mechanisms. We emulate the structural features of natural nacre by combining graphene oxide (GO) and a gellan gum (GG) biopolymer. We also reveal the mechanism of integrative mechanical performance. Several GO nanosheets with GG coating and crosslinking are used as optimal building blocks with intrinsic hard/soft features. These materials are induced to rapidly self-assemble into aligned nacre-like films by vacuum filtration to produce strong and tough bio-inspired composite films with fracture strength of 88.7 MPa, fracture stain of 0.84%, tensile modulus of 25.4 GPa and good biocompatibility. This study has merit of unrestricted fabrication of a homogeneous colloidal suspension of crosslinked nanohybrid building blocks of GO. Composite films constructed using these building blocks are innovative because of combined interactions, including coordination bonding, ionic bonding, and hydrogen bonding among their constituents. These films differ from other reported bio-inspired GO composite films with single adhesion interaction and thus provide good integrative mechanical performance through a multiple energy dissipation mechanism.     

Novel and green approach for the nanocrystalline magnesium oxide synthesis and its catalytic performance in Claisen–Schmidt condensation

Magnesium oxide is one of the most promising solid base material having catalytic applications. A novel, simple, efficient, inexpensive, additives free and green synthesis protocol for magnesium oxide nano-particles using concentrated solar energy has been reported. Using magnesium acetate and 1, 4-butanediol magnesium oxide nanoparticles in the range of 5–20 nm was prepared. The driving force for the nanoparticles synthesis was obtained by using concentrated solar energy as a dual energy source in the form of radiational and thermal effect. The resulting magnesium oxide nanoparticles are found to be excellent and reusable catalyst for the Claisen–Schmidt condensation under solvent free condition.     

New lanthanide sulfate–oxalate hybrid solids containing different inorganic building blocks

Three new lanthanide sulfate–oxalate hybrid solids, Er₂(SO₄)(C₂O₄)₂(H₂O)₆·0.5H₂O (1), Nd₃(SO₄)(C₂O₄)_3.5(H₂O)₇·H₂O (2), and [C₄H₁₄N₂]_0.5·Nd₂(SO₄)₂(C₂O₄)_1.5(H₂O)₄ (3), have been synthesized and structurally characterized. Compound 1 has a rare ladder-like structure, while compounds 2 and 3 have different three-dimensional structures. The presence of large 12-ring channels in the structure of 3 is noteworthy. The powder X-ray diffraction, IR spectra, thermogravimetric analyses, and magnetic susceptibility measurements of compounds 1 and 2 have also been investigated.     

Synthesis,characterization and third-order nonlinear optical properties of novel hyperbranched donor–acceptor polyfluorenes based on 1,3,6,8-tertsubstituted carbazole core

Two novel hyperbranched donor–acceptor polyfluorenes based on 1,3,6,8-tertsubstituted carbazole core (4BrCzP1 and 4BrCzP2) were synthesized and characterized. The third order nonlinear optical properties of the materials were studied using Z-scan technique with femtosecond Ti: sapphire laser with delivering pulses of 140 fs at 800 nm. The nonlinear optical refractive index was 9.29 × 10^?8 esu for 4BrCzP1 and 3.19 × 10^?7 esu for 4BrCzP2, respectively. While the third order nonlinear susceptibility was 1.29 × 10^?9 esu for 4BrCzP1 and 4.33 × 10^?9 esu for 4BrCzP2, respectively. The experimental results indicated that the hyperbranched polyfluorenes was a promising candidate in the application of third order nonlinear optical materials.     

Direct and facile synthesis of Li–Sr–Zn ferrites via low temperature solution combustion route

Li–Sr–Zn nanoferrites i.e. Li_0.25Sr_0.5–xZn_xFe_2.25O₄, where ‘x’ varies from 0–0.5, have been synthesized using a low temperature solution combustion method which proves to be an efficient and economical technique for synthesizing these type of nanoferrites. The as-synthesized nanoferrites have cubic spinel structure as characterized by X-ray powder diffraction. Powder XRD and TEM (Transmission Electron Microscopy) characterization also evidence that the crystallite and particle size are in close agreement to each other. Mössbauer spectroscopy studies demonstrate that there is a gradual transition from ferrimagnetic to superparamagnetic character, which is also supported by the saturation magnetization and coercivity values. At room temperature, the nanoferrites were found to be superparamagnetic with negligible coercivities approaching towards zero while saturation magnetization values were found to be in the range 6.87–30.10 emu g⁻¹. The frequency dependent dielectric constant and loss values are in accordance with Koop׳s model. These nanoferrites show great potential in high density recordings, magnetic nanodevices and biomagnetic applications.     

Effect of dopant on ferroelectric,dielectric and photocatalytic properties of Co–La-doped dysprosium chromite prepared via microemulsion route

In the current study, pristine and a series of La and Co-doped dysprosium chromite (Dy_1-yLa_yCr_1-xCo_xO₃) nanoparticles have been fabricated via a facile microemulsion technique. The influence of doping was evaluated based on structural, ferroelectric, dielectric, and photocatalytic properties. The prepared nanoparticles were characterized by XRD, SEM, Raman, and UV–Vis techniques. XRD patterns confirm the synthesis of a monophase orthorhombic structure with space group Pbnm with an average crystalline size in the 18–37 nm range. The saturation polarization (Ps), remanence (Pr), and coercivity (Hc) were determined using a hysteresis loop, and it was observed that by increasing the concentration of dopants, the value of Ps and Pr were improved. According to the PL spectra, highly substituted materials had a low recombination rate and higher charge separation (e^? - h⁺), which was ultimately accountable for higher photocatalytic activity. The dielectric loss decreases with frequency and dopant concentration. The photocatalytic activity of Dy_1-yLa_yCr_1-xCo_xO₃ was investigated against Crystal Violet (CV) dye under sunlight irradiation. The Dy_1-yLa_yCr_1-xCo_xO₃ furnished a 70% dye degradation in 90 min, which is attributed to the tunned bandgap and efficient electron-hole pair separation and the photocatalytic activity under visible light making Dy_1-yLa_yCr_1-xCo_xO₃ a promising photocatalyst for dye removal from wastewater.     

Preparation and CO2 adsorption of amine modified Mg–Al LDH via exfoliation route

In response to the recent focus on reducing carbon dioxide emission, the preparation and characterization of organically functionalized materials for use in carbon capture have received considerable attention. In this paper the synthesis of amine modified layered double hydroxides (LDHs) via an exfoliation and grafting synthetic route is reported. The materials were characterized by elemental analysis (EA), powder x-ray diffraction (PXRD), diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) and thermogravimetric analysis (TGA). Adsorption of carbon dioxide on modified layered double hydroxides was investigated by TGA at 25–80 °C. 3-[2-(2-Aminoethylamino) ethylamino]propyl-trimethoxysilane modified MgAl LDH showed a maximum CO₂ adsorption capacity of 1.76 mmol g^?1 at 80 °C. The influence of primary and secondary amines on carbon dioxide adsorption is discussed. The carbon dioxide adsorption isotherms presented were closely fitted to the Avrami kinetic model.     

New assembly of transition metal complexes based on [GeW9O34]10− building blocks: Syntheses,crystal structures and magnetic properties

Two new polyoxotungstates Na₃H(C₃H₅N₂)₄[{Cu(C₃N₂H₄)₂}₂Cu₄(H₂O)₂(GeW₉ O₃₄)₂]·27H₂O (1) and Na₁₀H₈[Mn₆Ge₃W₂₄O₉₄(H₂O)₂]·37H₂O (2) have been synthesized in aqueous solution. The polyoxoanion frameworks of the two compounds are built on the lacunary Keggin-type polyanion [GeW₉O₃₄]^10?. The structure of compound 1 is a Weakley-type species capped by two [Cu(C₃N₂H₄)₂]²⁺ units through four bridging oxygen atoms on two opposite W₄O₄ faces. Compound 2 is a banana-shaped polyoxometalate consisting of two tri-Mn substituted [Mn₃GeW₉O₃₄]^4? Keggin units and a hexavacant bridging cluster [GeW₆O₂₆]^12?. The magnetic investigations demonstrate the presence of both antiferromagnetic and ferromagnetic exchange interactions for 1 and weak antiferromagnetic interactions for 2.     

A cyanide-bridged two-dimensional grid-like FeIII–CoII complex based on the pentacyanideferrite(III) building block

A cyanide-bridged Fe^III–Co^II heterometallic complex {[Fe(1-CH₃im)(CN)₅][Co(H₂O)₂]}n·3H₂O (1-CH₃im = 1-methylimadazole) (2) has been synthesized by the reaction of Co^II(ClO₄)₂·6H₂O with the pentacyanideferrite(III) building block (Ph₄P)₂[Fe^III(1-CH₃im)(CN)₅]·4.5H₂O (1). X-Ray single crystal diffraction analysis shows that complex 2 has a two-dimensional (2D) grid-like structure. Magnetic investigations show that complex 2 displays long-range antiferromagnetic ordering with T_N = 9.45 K. The typical metamagnetic behaviors were observed with the critical field of ca. 4000 Oe at 1.82 K.     

Reactive and stimuli-responsive maleic anhydride containing macromers – multi-functional cross-linkers and building blocks for hydrogel fabrication

Macromers with functional groups that allow for chemical derivatization, polymerization reactions or impart specific physico-chemical properties are functional building blocks for polymeric systems used in different biomedical applications. With this motivation, a series of oligomeric macromers was synthesized by free radical polymerization of maleic anhydride (MA) with N-isopropylacrylamide (NiPAAm) and pentaerythritol diacrylate monostearate (PEDAS). This chemical design provides anhydride groups for effective reactivity of the macromers with amines and other nucleophiles, copolymerized NiPAAm for temperature responsiveness and lipophilic stearate domains for increased hydrogel stability. Macromers were synthesized with different MA co-monomer feeds and oligomeric molecules (Mn below 5000 Da) were obtained with MA contents between 7% and 27% as determined by titration. The fraction of chemically intact anhydrides was calculated to range from 75% to 80%. The ability of the macromers to cross-link di- or oligovalent amines as a function of MA content was investigated rheologically. It was also demonstrated that monovalent amines, e.g. aminofluorescein, could be grafted to the macromer chain utilizing only a fraction of the anhydride functionalities. The derivatized macromers could still participate in cross-linking reactions due to the remaining anhydrides. Temperature sensitivity was shown for aqueous solutions of macromers with fully dissociated anhydride groups. The solutions were additionally responsive to changes in calcium ion concentration and pH. Extracts from macromer cross-linked polyether hydrogels showed no toxicity on L929 fibroblasts.The macromers have perspective as biocompatible cross-linkers for hydrogel fabrication from various biomacromolecules with the opportunity to decorate the gels with monoamine molecules that alter the biological or physico-chemical properties.     

Efficient and rapid route to thioamides via modified Willgerodt–Kindler reaction of quinaldine and picolines under microwave irradiation

Various thioamides, especially thiobenzanilides and thioacetomorpholides, bearing a heterocycle ring were efficiently prepared by a modified Willgerodt–Kindler reaction of quinaldine and α- and γ-picoline with anilines and morpholine in the presence of sulfur, and a catalytic amount of DABCO under microwave irradiation.     

Molecular packing based on a π-stacked screw via self-assembly

A new platinum(II) complex, C₂₄H₁₆N₁₀S₂Pt·3H₂O, bis(4,5-diazafluorene-9-one thiosemicarbazato) platinum(II) trihydrate, has been synthesized. Crystals of it are trigonal, space group P3₂ with cell parameters of a=10.696(4), c=19.748(6) Å and Z=3. The ligands are coordinated to the platinum(II) atom by two imino nitrogen atoms N(3) and N(8), and two sulfur atoms S(1) and S(2) forming a rigid molecular tweezers maintained by intramolecular π–π stacking. Detailed crystal structure analyses exhibit that the one-dimensional 3₂ screw robust supramolecular aggregate was achieved by intermolecular π–π stacking interaction between the extensive delocalization π-system ligands via self-assembly and the aggregates were linked by hydrogen bonding.     

Ignition of droplets of coal–water–oil mixtures based on coke and semicoke

To permit expansion of the resource base and utilize industrial waste, coal–water–oil fuels may be prepared on the basis of coke and semicoke, as well as common petroleum derivatives (fuel oil and spent compressor, turbine, and transformer oils). The minimal oxidant temperature corresponding to stable ignition of coal–water–oil slurries is established. Typical variation in fuel temperature in the course of reaction is determined, as well as the delay time of ignition and the total combustion time for individual droplets of such fuel suspensions. For droplets of initial size 0.5–1.5 mm, the influence of the various factors (droplet size, oxidant temperature, and concentration of the components) on the threshold (minimum) temperature and inertia of ignition is studied. It is shown that stable ignition of coke and semicoke in such fuel is possible at moderate oxidant temperatures: 700–1000 K.     

Photocatalytic degradation of methanol on titania and titania–silica aerogels prepared by non-alkoxide sol–gel route

Titania and titania–silica aerogels were prepared by alkoxide or non-alkoxide sol–gel route and subsequent supercritical drying with carbon dioxide at low temperature. The resulting aerogels having high surface area and mesoporosity were used as photocatalysts for gas phase methanol degradation reaction. Photocatalytic degradation reactions were carried out on titania and titania–silica aerogels, and commercial Degussa P-25 titania. The photocatalytic activities of titania and titania–silica aerogels were higher than that of the P-25. While the conversion of methanol degradation over the P-25 catalyst was only 50–60%, that for the titania aerogel was observed to be above 98% due to the higher specific surface area and the well developed mesoporous structure. In spite of lower titania contents, much higher surface area and high dispersion of titania of titania–silica aerogel gave rise to the high photocatalytic activity in comparison to those of titania aerogels. Moreover, titania–silica aerogel was also used for the photodegradation and adsorption hybrid system. It was observed that the high removal efficiency for methanol was caused by the combination of higher catalytic activity and adsorption capacity.     

Synthesis and characterization of hybrid organic–inorganic materials based on sulphonated polyamideimide and silica

The preparation of hybrid organic–inorganic membrane materials based on a sulphonated polyamideimide resin and silica filler has been studied. The method allows the sol–gel process to proceed in the presence of a high molecular weight polyamideimide, resulting in well dispersed silica nanoparticles (<50 nm) within the polymer matrix with chemical bonding between the organic and inorganic phases. Tetraethoxysilane (TEOS) was used as the silica precursor and the organosilicate networks were bonded to the polymer matrix via a coupling agent aminopropyltriethoxysilane (APTrEOS). The structure and properties of these hybrid materials were characterized via a range of techniques including FTIR, TGA, DSC, SEM and contact angle analysis. It was found that the compatibility between organic and inorganic phases has been greatly enhanced by the incorporation of APTrEOS. The thermal stability and hydrophilic properties of hybrid materials have also been significantly improved.     

Preparation and anti-evaporation properties of organic–inorganic superabsorbent based on Tragacanth gum and clay

In this study, the application of superabsorbent resin (SAP) in inhibiting the soil moisture evaporation (or slowing down the water outflow) was studied. The clay-SAP composites were fabricated by grafting of poly (acrylic acid-N-hydroxymethyl acrylamide/clay) (GT-g-P [AA-co-NHA]/clay) on Tragacanth gum (GT), using solution polymerization. The structure, morphology and stability of the clay-SAP composites were investigated by Fourier transform infrared, scanning electron microscope and TGA. The maximum swelling ratio of Attapulgite (3%)-, Kaolin (3%)- and Montmorillonite (3%)-SAP composite in deionized water reached 1180, 819 and 525 g/g respectively, and the maximum swelling ratio in tap water reached up to 206, 192 and 170 g/g respectively. Meanwhile, the maximum swelling ratio in 0.9% NaCl solution was 95, 82 and 62 g/g respectively. The water retention of clay-SAP composites was also analyzed as a function of temperature. In addition, by simulating the desertification area, the effect of the APT (3%)-SAP composite on the anti-evaporation performance was studied. The obtained results revealed that the water retention of APT (3%)-SAP composite was 36% at 45°C for 12 h. Under natural conditions, the evaporation rate of the anti-evaporation material was inversely proportional to the amount of APT (3%)-SAP composite added.     

Synthesis and properties of novel donor–acceptor copolymers based on thiophene and squaraine moieties

Two novel donor–acceptor copolymers were synthesized by Sonogashira cross-coupling of alkyl/alkoxy thiophene and dibromo-substituted squaraine moieties. The structures and properties of these polymers were characterized using FT–IR, NMR, UV–Vis, gel permeation chromatography, and cyclic voltammetry. Both copolymers are readily soluble in common organic solvents. The polymer films exhibit broad absorption in the wavelength range from 300 to 1000 nm with the maximum peaks over 750 nm. Electrochemical studies reveal that the band gaps of the polymers range from 1.05 to 1.36 eV. Compared to the alkyl thiophene, the alkoxy thiophene units can effectively lower the band gap and result in significant red-shift absorption spectrum of the resulted polymer. The strong overlap of the solar spectrum and the extremely low band gaps of the polymers suggest that they may be promising candidates for solar cells.     

A sensitive and selective pyrosine sensor based on palygorskite–graphene modified electrode

Palygorskite–graphene composite was obtained by the electrochemical reduction of palygorskite–graphene oxide (GO), and the resulted palygorskite–graphene modified glassy carbon electrode (GCE) was used as the amperometric sensor for pyrosine determination. Compared to the graphene modified GCE, the detecting sensitivity of pyrosine was greatly improved at the palygorskite–graphene modified GCE. This was mainly attributed to the high adsorption capability of palygorskite. The effect of the mass ratio of GO to palygorskite was investigated, and the optimum mass ratio of GO to palygorskite was chosen as 2:1. The calibration curve was linear for pyrosine concentration from 21 to 598 μM, and the detection limit was as low as 5.98 nM (signal-to-noise ratio of 3). The palygorskite–graphene modified GCE also had satisfactory fabrication reproducibility, good determination precision and high detecting selectivity for pyrosine.