Ladder-Like Versus Hexagonal Organic–Inorganic Hybrid Materials in the Extraction of Lead Ions

Meso-structured and ladder organic–inorganic hybrid materials functionalized with ammonium carboxylate groups were prepared. These materials were obtained by the sol–gel process starting from the cyanopropyltriethoxysilane precursor as a building block. Hydrolysis of CN to COOH groups followed by treatment with triethylamine gives rise to cationic exchange materials. These materials exhibit a high chelating capability towards cations and can be used for water treatment. Lead ion (Pb²⁺) was tested as example; and, some tests were made on the meso-structured and ladder material for further comparison in efficacy of extractions.     

Self-Assembled Organic–Inorganic Hybrid Nanocomposite of a Porphyrin Derivative and CdS

A porphyrin derivative, 5-(4-carboxylphenyl)-10,15,20-tris(4-chlorophenyl) porphyrin (PorCOOH), was synthesized and self-assembled as a monolayer thin solid film on the modified surface of a quartz substrate by an ester bond between –COOH groups of PorCOOH molecules and –OH groups of the hydrophilic pretreated SiO₂ surface. An analysis of the spectral change revealed the J-aggregate nature of PorCOOH molecules in the obtained thin solid film. With this thin solid film of PorCOOH as a template, CdS nanoparticles were deposited on it in situ, which were further characterized by electronic absorption, fluorescence, and energy-dispersive X-ray spectroscopy. The morphology of CdS nanoparticles is disklike, and the diameter is ca. 40–60 nm, determined by scanning electronic microscopy. Furthermore, electron transfer between the organic layer and CdS nanoparticles was deduced through fluorescence quenching and theoretical analysis.     

A New 3D Pb(II) Inorganic–Organic Hybrid Framework Based on Terephthalate Acid with the Inorganic Pb–O–Pb Connectivity

Solvothermal reaction of Pb(NO₃)₂ with terephthalate acid afforded one new inorganic–organic hybrid framework, [Pb(PBDC)]_n (1) (H₂PBDC = terephthalic acid). X-ray analysis shows that compound 1 crystallizes in orthorhombic space group Pbca and the two carboxy group of terephthalate acid adopt rare coordination modes. A noticeable point in this paper that compound 1 exhibits preferable catalytic property on degradation of Rhodamine B. The phase purity of the as-synthesized sample was confirmed by powder X-ray diffraction. Moreover, satisfactory elemental analysis, IR spectra, and thermogravimetric analysis were obtained.     

New Inorganic–Organic Hybrid Materials and Their Oxides for Removal of Heavy Metal Ions: Response Surface Methodology Approach

In this paper, Cu(II), Fe(III), Pb(II), and Zn(II) heavy metal ions were removed from their aqueous solutions by using novel inorganic–organic hybrid materials, Al-GPTS-H and Al-GPTS-NaOSiMe₃-H (hybrid material-1 and 2, respectively), and their oxides (calcined-1 and 2) as adsorbents. These ions removal by adsorption was optimized by using response surface methodology (RSM). Central composite design (CCD) method was used in order to investigate the effects of initial pH, initial metal concentration of solutions and adsorbent quantity on the adsorption efficiency (R, %). As a result of the experiments under optimum conditions, the maximum % R values were obtained by hybrid material-1 for Fe(III) (99.89%) and by calcined material-1 for Pb(II) (97.14%), respectively. These quite high adsorption efficiency values have shown that these hybrid materials and their oxides are suitable to use for heavy metal ions removal from aqueous solutions.     

Effect of Surfactants and Temperature on Adsorption Behavior of Metal Ions on Organic–Inorganic Hybrid Exchanger,Acrylamide Aluminum Tungstate

The adsorption behavior of a thermally and chemically stable hybrid ion-exchange material, acrylamide aluminum tungstate was explored in cationic (CTAB) and anionic (SDS) surfactants and acidic solvents. Critical micellar concentration (CMC) appears to be an important parameter in determining the adsorption behavior of metal ions. Equilibration time and temperature studies on the distribution coefficient of metal ions were studied. On the basis of the distribution coefficient, this material was successfully used for quantitative separations of some binary synthetic mixtures of metal ions by the column method. Hg(II) ion was selectively determined quantitatively in synthetic mixture. The material appears to be promising for separating toxic metal ions in a real matrix (industrial effluents and waste water) and can be utilized as a packing material in HPLC and GC columns for faster and more efficient separation.

Inorganic–Organic Hybrid Materials of Zirconium and Aluminum and Their Usage in the Removal of Methylene Blue

Two novel inorganic–organic hybrid materials, Al-Pydca-3-APDEMS-H and Zr-Pydca-3-APDEMS-H, were prepared by the sol gel method in two steps. In the first step, Al(O^sBu)₂-Pydca and Zr(OPrⁿ)₃-Pydca complexes were prepared from the reactions of aluminum sec-butoxide Al(O^sBu)₃ and zirconium n-propoxide Zr(OPrⁿ)₄ with 2,6-pyridinedicarboxylic acid, respectively. After 3 h of stirring, 3-aminopropyldiethoxymethyl silane (3-APDEMS) and dilute hydrochloric acid were added to the Al(O^sBu)₂-Pydca and Zr(OPrⁿ)₃-Pydca mixtures to hydrolyze the reactions and to form condensation products. These hybrid products were characterized by a combination of Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, Barrett-Joyner-Halenda (BJH) and other analysis methods. These hybrid materials were used for the removal of methylene blue (MB), a cationic organic dye. The removal efficiency of hybrid materials was measured by UV–Vis spectroscopy.

     

Ionothermal Syntheses and Crystal Structures of Two 1D Inorganic–Organic Hybrid Frameworks

Two 1D inorganic–organic hybrid frameworks, namely, [Zn(5-NO₂-bdc)(MIM)₃·H₂O]_n(1) and [Cd(MIM)₂Br₂]_n(2) (5-NO₂-bdcH₂ = 5-nitro-1,3-benzenedicarboxylic acid, MIM = N-methyl imidazole) were synthesized via ionothermal reactions with ionic liquid 1-ethyl-3-methylimidazolium bromide ([EMIM]Br) as solvent and template. Both compounds have been characterized by elemental analyses, spectroscopic analyses, thermogravimetric analysis (TGA) and the single crystal diffraction. The zinc(II) center in compound 1 is a slightly distorted five-coordinate trigonal bipyramid, 5-NO₂-bdc²⁻ anions and MIM moieties effectively bridge Zn centers to result in 1D zigzag chains. While Cd(II) center in compound 2 is in an octahedral coordination environment, and two μ²-bridge bromine link two [Cd(MIM)₂] moieties to form a 1D chain structure. In addition, complex 2 exhibits strong fluorescent emission in the solid state at room temperature.     

Synthesis and Characterization of pH-Responsive Organic–Inorganic Hybrid Material with Excellent Catalytic Activity

Poly(N-isopropylmethacrylamide-co-methacrylic acid) [p(NipAam-Mac)] microgels were synthesized and used as microreactors to fabricate silver nanoparticles. Pure and hybrid microgels were characterized using Ultraviolet–Visible (UV/Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and transmission electron microscopy (TEM). Catalytic activity of hybrid microgels and mechanism of catalysis by this system was explored using different reaction conditions. At the same temperature, apparent rate constant (k_app) was found to be varied from 0.0414 to 0.7852 min^?1 by increasing the concentration of NaBH₄ from 2.49 to 22.41 mM at constant concentration of substrate and catalyst. However upon extra increase in concentration of NaBH₄ from 22.41 to 37.35 mM reduced the value of k_app to 0.2178 min^?1. Likewise, the value of k_app was found to be increased from 0.1242 to 0.5495 min^?1 with increasing the concentration of 4-nitrophenol [Para-nitrophenol (p-Np)] from 0.063 to 0.079 mM keeping other parameters constant. Further increase in concentration of p-Np caused decline in the value of k_app. Kinetic data reveals that catalytic reduction of p-Np obeys Langmuir–Hinshelwood mechanism and p-Np is converted to p-Ap on the surface of the silver nanoparticles passing through various reaction intermediates.     

One-Step Hydrogenation/Esterification Activity Enhancement Over Bifunctional Mesoporous Organic–Inorganic Hybrid Silicas

Bifunctional mesoporous organic–inorganic hybrid silica incorporating both platinum and organosulfonic acid groups were synthesized for use in simultaneously catalyzing the one-step hydrogenation/esterification (OHE) of acetic acid and acetaldehyde, which was considered as a model reaction for the upgrading of biomass-derived bio-oil. The work explored optimizing the synthesis procedure to generate a bifunctional catalyst with enhanced combined activity for the OHE reaction. The presence of Pt was found to enhance the acidic properties of the organosulfonic acid functionalized silica. The mechanism by which the Pt incorporation affected the acid sites was investigated by the using XPS, FT-IR, FT-Raman characterization. The XPS results indicated the presence of electron transfer between the Pt and –SO₃H groups. The FT-IR and FT-Raman results, which were in agreement with XPS, demonstrated an electron density increase for S and a S–O bond energy increase, which was proposed to be the reason for the acidity enhancement due to the presence of Pt. Additionally, arenesulfonic acid groups were substituted for propylsulfonic acid groups and the resulting material had higher catalytic activity due to the increased acid strength. An optimal synthesis procedure was demonstrated in which the Pt was first impregnated on the mesoporous silica using reductive deposition. Then Pt was activated and the material further modified by grafting on arenesulfonic acid groups. The resulting catalyst was about four times more active than the original base case bifunctional material.     

Organic–Inorganic Coatings Based on Epoxidised Castor Oil/APTES/TEOS

Two series of organic–inorganic hybrid films were prepared from epoxidised castor oil (ECO) and the inorganic precursor 3-aminopropyltriethoxysilane (APTES), and the combination of APTES with tetraethoxysilane (TEOS) with different organic to inorganic proportions. Films were pre-cured at room temperature under inert atmosphere and subsequently submitted to thermal curing. The macro- and microscopic properties of the films, including adhesion, hardness, microstructure and thermal properties, were determined as a function of the proportion of ECO to inorganic precursors. Morphologic studies showed that the hybrid films were microscopically homogeneous. The hardness and tensile strength of the films increased with increased concentrations of inorganic precursor. All of the films exhibited good adhesion to an aluminium surface and worked as an efficient barrier against corrosion.     

Formulation of Mechanochemically Evolved Fly Ash Based Hybrid Inorganic–Organic Geopolymers with Multilevel Characterization

In this research, advanced hybrid inorganic–organic geopolymeric material is developed by environmentally and user friendlier approach. The presented novel approach for geopolymer formation certainly overcomes the existing drawbacks of geopolymerization technology. The effect of rice husk ash and Na₂O/SiO₂ ratios on geopolymer gel formation and mechanical strength has been previously identified via solution chemistry route; however, development of geopolymeric material having hybrid inorganic–organic characters via together mechanochemical grinding of raw materials and effect of mechanochemically activated Na₂SiO₃ on geopolymeric properties via solid state route has never before been explored. Together mechanochemical grinding of raw materials of varying compositions in solid state resulted in the formation of ready to use geopolymeric precursors; which on just addition of water led to development of advanced hybrid inorganic–organic geopolymeric material with considerably enhanced properties. XRD, FTIR and SEM characterization data of developed geopolymeric precursor powder and hybrid inorganic–organic geopolymeric material are reported and discussed in detail. As the results of the investigations, the relationship between geopolymer composition, grinding mechanism and material properties established. The composition which exhibited synergistic effect of both rice husk and SMS is found to be excellent in performance. The study showed that it is practical and better to adopt this greener solid state approach for preparation of geopolymer instead of user-unfriendlier hazardous alkaline solution based approach, to achieve sustainable growth in geopolymers as like Portland cement.     

Efficient Removal of Methylene Blue Using a Hybrid Organic–Inorganic Hydrogel Nanocomposite Adsorbent Based on Sodium Alginate–Silicone Dioxide

In this work, we reported synthesis, structure characterization and methylene blue (MB) adsorption of a novel organic–inorganic hydrogel nanocomposite adsorbent (HNA) based on sodium alginate (NaAlg) and silicone dioxide nanoparticles (SiO₂-NPs). The HNAs were prepared using grafting of acrylic acid (AA) onto NaAlg by using ammonium persulfate as a free radical initiator and methylene bisacrylamide as a crosslinker in the presence of SiO₂-NPs, which synthesized in situ from the base-catalyzed hydrolysis of tetraethylorthosilicate (TEOS). The structure of HNAs were characterized by FTIR, SEM, EDX, TEM, XRD, UV–Vis and TGA techniques and a proposed mechanism for preparation of adsorbents was also suggested. The swelling capacity of HNAs was examined in buffer solutions with pH ranged 1.0–14.0. The nanocomposites exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 2.0 and 9.0. The swelling kinetics of HNA was also preliminary investigated. Moreover, the effects of agitation time, pH, initial dye concentration, adsorbent dose, TEOS content, AA concentration and temperature were optimized with respect to dye adsorption capacity of HNAs in detail. Furthermore, the kinetic and adsorption isotherm of MB dye onto HNAs were investigated in detail. The HNAs also showed excellent regeneration capacity after five consecutive cycles of dye adsorption–desorption. In general, the results indicated that the synthesized adsorbents with biodegradability and biocompability properties can be used in wastewater treatment via dye adsorption.     

A New Route to Highly Stretchable and Soft Inorganic–Organic Hybrid Elastomers Using Polydimethylsiloxane as Crosslinker of Epoxidized Natural Rubber

Sulfur or peroxide crosslinking is the most common and conventional method to develop elastomeric materials. A new approach to crosslink epoxidized natural rubber (ENR) by aminopropyl terminated polydimethylsiloxane (AT-PDMS) is described, intending to develop a new kind of hybrid organic–inorganic elastomers. The curing reaction is accelerated by using hydroquinone as a catalyst. The formation of the hybrid structure is evident from the appearance of two glass transition temperatures, at −1 and −120 °C, for the ENR and PDMS phases, respectively. The curing reaction is found to be of first order with respect to amine concentration with the estimated activation energy of ≈62 kJ mol⁻¹. Comparing the mechanical properties to a typical ENR-sulfur system leads to the conclusion that the ENR/AT-PDMS hybrid structure is highly stretchable and soft, as demonstrated by its relatively higher strain at failure (up to ≈630%), and lower hardness and modulus values. The higher stretchability and soft nature of the material are achieved by introducing flexible PDMS chains during the curing process resulting to a hybrid elastomer networks. This kind of soft but robust materials can find several applications in diverse fields, such as soft robotics, flexible, and stretchable electronics.     

Direct Electrochemistry and Electrocatalysis of Hemoglobin on Bimetallic Au–Pt Inorganic–Organic Nanofiber Hybrid Nanocomposite and Mesoporous Molecular Sieve MCM-41

A glassy carbon electrode modified with MCM-41 and bimetallic inorganic–organic nanofiber hybrid nanocomposite was prepared and used for determination of trace levels of hydrogen peroxide (H₂O₂). The direct electron transfer (DET) and electrocatalysis of hemoglobin (Hb) entrapped in the MCM-41 modified Au–Pt inorganic–organic nanofiber hybrid nanocomposite electrode (Au–PtNP/NF/GCE) were investigated by using cyclic voltammetry in 0.1 M pH 7.0 phosphate buffer solution. Due to its uniform pore structure, high surface area and good biocompatibility, the mesoporous silica sieve MCM-41 provided a suitable matrix for immobilization of biomolecules. The MCM-41 modified Au–Pt inorganic–organic nanofiber hybrid nanocomposite electrode showed significant promotion to DET of Hb, which exhibited a pair of well-defined and quasi-reversible peaks for heme Fe(III)/Fe(II) with a formal potential of ?0.535 V (vs. Ag/AgCl). Additionally, the Hb immobilized on the MCM-41 modified electrode showed excellent electrocatalytic activity toward H₂O₂ reduction.     

An Efficient and Recyclable Silica Based Inorganic–Organic Hybrid Zinc Catalyst for Transesterification of β-Ketoesters

A new silica based inorganic–organic hybrid zinc catalyst was synthesized and its catalytic activity was investigated for transesterification of β-ketoesters. Polymer supported catalyst was characterized by various techniques such as surface area (BET), elemental and thermogravimetric analyses, FTIR, ¹³C CPMAS spectral studies and atomic absorption spectroscopy (AAS). The reaction proceeded smoothly in the presence of 0.04 mmol of catalyst in toluene at refluxing conditions. The catalyst revealed higher catalytic activity compared to homogeneous catalyst and was reused without appreciable loss in catalytic activity.     

Syntheses and Crystal Structures of Two Inorganic–Organic Hybrid Frameworks Constructed from Pyridine-2,5-Dicarboxylic Acid

Two novel inorganic–organic hybrid frameworks of [Co(2,5-pydc)(4,4′-bipyo)_0.5(H₂O)₃ · 3H₂O] _n (1) and [Cu_1.5Gd(2,5-pydc)₃(2,2′-bipyo)(H₂O)₄ · 2H₂O] _n (2) (2,5-pydc = pyridine-2,5-dicarboxylic acid; 4,4′-bipyo = 4,4′-bipyridine-N,N′-dioxide; 2,2′-bipyo = 2,2′-bipyridine-N,N′-dioxide) were prepared. Both compounds have been characterized by the elemental analyses, IR spectra, TG analysis and the single crystal diffraction. The salient structural feature for both compounds 1 and 2 is that the 1D chain and the mononuclear fragment are connected by strong hydrogen bond interactions to form 2D structure.