New Functional Alkoxysilanes and Silatranes: Synthesis, Structure, Properties, and Possible Applications

The aza-Michael reaction of 3-aminopropyltriethoxysilane (1) and -silatrane (2) with acrylates affords functionalized silyl-(3-8) and silatranyl-(9-14) mono- and diadducts with up to a 99% yield. Their structure has been proved with IR and NMR spectroscopies, mass spectrometry and XRD analysis. The hydrolytic homo-condensation of triethoxysilanes 3-5 gives siloxanes 3a-5a, which form complexes with Ag, Cu, and Ni salts. They are also able to adsorb these metals from solutions. The hetero-condensation reaction of silanes 4-8 with OH groups of zeolite (Z), silica gel (S) and glass (G) delivers the modified materials (Z4, S7, G4, G5, G7, G8, etc.), which can adsorb ions of noble metal (Au, Rh, Pd: G4 + Au, G5 + Pd, G7 + Rh). Thus, the synthesized Si-organic polymers and materials turned out to be promising sorbents (enterosorbents) of noble, heavy, toxic metal ions and can be applied in industry, environment, and medicine.

Novel Mesoporous Organosilicas with Task Ionic Liquids: Properties and High Adsorption Performance for Pb(II)

Removal of toxic contaminants such as Pb(II) from waste solutions is environmentally requested. Therefore, in this paper, for potential novel sorbents, mesoporous ionic liquid-functionalized silicas were synthesized and tested for the removal of Pb(II) from aqueous solutions. The successful synthesis of the adsorbents was proved by nuclear magnetic resonance (²⁹Si and ¹³C NMR), Fourier transform infrared spectroscopy (FTIR), and elemental analysis. The structural and textural properties were determined using scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), and low-temperature N₂ sorption, and the result showed that the applied procedure made it possible to obtain highly ordered particles with a two-dimensional mesostructure. The effects of several parameters including initial pH, contact time, adsorption temperature, and Pb(II) concentration were studied in detail and were discussed to evaluate the adsorption properties of the fabricated materials towards Pb(II). The obtained results confirmed a very high potential of the sorbents; however, the adsorption properties depend on the structure and amounts of the functional group onto fabricated materials. The sample ILS-Ox3-40 showed fast kinetics (equilibrium reached within 10 min) and capacity of 172 mg/g, and that makes it a promising sorbent for the cleanup of water contaminated by lead. It was also indicated that, regardless on structure of the tested materials, the Pb(II) removal was spontaneous and exothermic. The fabricated mesoporous silicas exhibited that they were easy to regenerate and had excellent reusability.

Studies of New Iridium Catalysts Supported on Modified Silicalite-1-Their Structure and Hydrogenating Properties

This paper investigates the catalytic properties of the iridium catalysts supported on modified silicalite-1. Post-synthesis modification of silicalite-1, with solutions of ammonium compounds (NH₄F and NH₄OH), appeared to be an efficient method to generate the acidic sites in starting support. The modification of support led not only to changes in its acidity but also its porosity-formation of additional micro- and mesopores. The novel materials were used as supports for iridium. The iridium catalysts (1 wt.% Ir) were characterized by N₂ adsorption/desorption measurements, temperature-programmed reduction with hydrogen (TPR-H₂), H₂ chemisorption, transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (TPD-NH₃), X-ray photoelectron spectroscopy (XPS) and tested in the hydrogenation of toluene reaction. The catalytic activity of iridium supported on silicalite-1 treated with NH₄OH (higher porosity of support, better dispersion of active phase) was much higher than that of Ir supported on unmodified and modified with NH₄F silicalite-1.

Mesoporous Silica Platforms with Potential Applications in Release and Adsorption of Active Agents

In recent years, researchers focused their attention on mesoporous silica nanoparticles (MSNs) owing to the considerable advancements of the characterization methods, especially electron microscopy methods, which allowed for a clear visualization of the pore structure and the materials encapsulated within the pores, along with the X-ray diffraction (small angles) methods and specific surface area determination by Brunauer–Emmett–Teller (BET) technique. Mesoporous silica gained important consideration in biomedical applications thanks to its tunable pore size, high surface area, surface functionalization possibility, chemical stability, and pore nature. Specifically, the nature of the pores allows for the encapsulation and release of anti-cancer drugs into tumor tissues, which makes MSN ideal candidates as drug delivery carriers in cancer treatment. Moreover, the inner and outer surfaces of the MSN provide a platform for further functionalization approaches that could enhance the adsorption of the drug within the silica network and the selective targeting and controlled release to the desired site. Additionally, stimuli-responsive mesoporous silica systems are being used as mediators in cancer therapy, and through the release of the therapeutic agents hosted inside the pores under the action of specific triggering factors, it can selectively deliver them into tumor tissues. Another important application of the mesoporous silica nanomaterials is related to its ability to extract different hazardous species from aqueous media, some of these agents being antibiotics, pesticides, or anti-tumor agents. The purpose of this paper is to analyze the methods of MSN synthesis and related characteristics, the available surface functionalization strategies, and the most important applications of MSN in adsorption as well as release studies. Owing to the increasing antibiotic resistance, the need for developing materials for antibiotic removal from wastewaters is important and mesoporous materials already proved remarkable performances in environmental applications, including removal or even degradation of hazardous agents such as antibiotics and pesticides.

A POSS-Phosphazene Based Porous Material for Adsorption of Metal Ions from Water

The development of adsorptive materials continues to be an important area of research for removal of heavy metal ions from waste water. The adsorption capacity can be modulated by both physical and chemical modification of the adsorbent. Herein, we combine the unique properties of polyhedral oligomeric silsesquioxane (POSS) and organocyclophosphazene as the building units to synthesize a hybrid porous material, abbreviated as PN-POSS. The synthetic method follows a Heck reaction between hexa(4-bromophenoxy)cyclotriphosphazene and octavinylsilsesquioxane (OVS). The Brunauer-Emmett-Teller (BET) analysis shows that the material possesses micro- and mesopores of 1.5 and 3.8 nm size and a surface area on the order of 500 m²  g^-1 . These attributes in combination with the donor ability of the phosphazene units qualify the material for high adsorption of Pb²⁺ , Hg²⁺ and Cu²⁺ ions with maximal adsorption capacities on the order of 1326, 1927 and 2654 mg g^-1 , respectively. The adsorbent exhibits a good regeneration performance and can be effectively used for water treatment.