Amine-functionalized, chiral mesoporous organosilicas were prepared from a rationally designed precursor, which combines the functions of a network builder, a chiral latent functional group, and a porogen in one molecule. The precursors are formed by a convenient enantioselective hydroboration using (S)-monoisopinocampheylborane on an ethylene-bridged silica precursor. These precursors do selforganize when hydrolysis of their inorganic moiety takes place via an aggregation of their organic moiety into hydrophobic domains. After a condensation-ammonolysis sequence mesoporous organosilicas functionalized with chiral amine groups are obtained, with the complete chiral functionalities located at the pore wall surface and therefore accessible to chemical processes. The pore size of the resulting organosilicas can be fine-tuned using different organic moieties attached to the boron group in the first step. While a wormlike arrangement of pores is observed for the pure precursor, common surfactants can be admixed to further control and tailor the resulting mesoporous system. In certain phase ranges, also chiral periodic mesoporous organosilicas can be obtained.
A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H(2)O beads) or liquid nitrogen (LN(2) beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m(2) g(-1), respectively, and had varied pore architectures. The H(2)O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN(2)-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.
A mixed titanium-zirconium (Ti : Zr ¼ 2 : 1 atomic ratio) oxide non-woven nanofibrous web was prepared by using an electrospinning technique followed by thermal treatment. A hydrocarbon surfactant was incorporated into the electrospinning solution and was pyrolysed during heating. The surfactant acted as a structure-directing agent to create intra-fibre pores, and significantly increased the surface area of the fibres, thereby maximising the number of sites for further surface modification as well as heavy metal ion adsorption. The high surface area (248 m 2 g À1 ) titanium-zirconium oxide nanofibre surface was functionalised via a phosphonic acid coupling reaction to give different functional groups for attracting metal ions (i.e., phosphonate and amine groups). The cadmium adsorption capacity of the phosphonate-functionalised nanofibres was up to 10 times higher than that of the non-modified or amine-functionalised nanofibres. In addition, the cadmium adsorption on the phosphonatefunctionalised nanofibres was less dependent on the pH of analyte solutions than the metal oxide nanofibres where the surface charge changed in varied pH environments. The size of the nanofibrous web can be easily scaled for making a large web convenient for handling and recovery after use, compared with high surface area heavy metal ion adsorbents that are nanometre or micrometre in size.
To take advantage of the full potential of functionalized transition metal oxides, a well-understood nonsilane based grafting technique is required. The functionalization of mixed titanium zirconium oxides was studied in detail using a bisphosphonic acid, featuring two phosphonic acid groups with high surface affinity. The bisphosphonic acid employed was coupled to a UV active benzamide moiety in order to track the progress of the surface functionalization in situ. Using different material compositions, altering the pH environment, and looking at various annealing conditions, key features of the functionalization process were identified that consequently will allow for intelligent material design. Loading with bisphosphonic acid was highest on supports calcined at 650 °C compared to lower calcination temperatures: A maximum capacity of 0.13 mmol g(-1) was obtained and the adsorption process could be modeled with a pseudo-second-order rate relationship. Heating at 650 °C resulted in a phase transition of the mixed binary oxide to a ternary oxide, titanium zirconium oxide in the srilankite phase. This phase transition was crucial in order to achieve high loading of the bisphosphonic acid and enhanced chemical stability in highly acidic solutions. Due to the inert nature of phosphorus-oxygen-metal bonds, materials functionalized by bisphosphonic acids showed increased chemical stability compared to their nonfunctionalized counterparts in harshly acidic solutions. Leaching studies showed that the acid stability of the functionalized material was improved with a partially crystalline srilankite phase. The materials were characterized using nitrogen sorption, X-ray powder diffraction, and UV-vis spectroscopy; X-ray photoelectron spectroscopy was used to study surface coverage with the bisphosphonic acid molecules.
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