In fields of materials science and chemistry, ionic-type porous materials attract increasing attention due to significant ion-exchanging capacity for accessing diversified applications. Facing the fact that porous cationic materials with robust and stable frameworks are very rare, novel tactics that can create new type members are highly desired. Here we report the first family of polyhedral oligomeric silsesquioxane (POSS) based porous cationic frameworks (PCIF-n) with enriched poly(ionic liquid)-like cationic structures, tunable mesoporosities, high surface areas (up to 1,025 m2 g−1) and large pore volumes (up to 0.90 cm3 g−1). Our strategy is designing the new rigid POSS unit of octakis(chloromethyl)silsesquioxane and reacting it with the rigid N-heterocyclic cross-linkers (typically 4,4′-bipyridine) for preparing the desired porous cationic frameworks. The PCIF-n materials possess large surface area, hydrophobic and special anion-exchanging property, and thus are used as the supports for loading guest species PMo10V2O405−; the resultant hybrid behaves as an efficient heterogeneous catalyst for aerobic oxidation of benzene and H2O2-mediated oxidation of cyclohexane.
Extreme conditions such as high temperature and/or pressure are usually required for the transformation of amorphous silica to crystalline polymorphs. In this article, we present our results that amorphous silica can be deposited on a bacterial surface and transformed to cristobalite at a relatively low temperature and ambient pressure.The phase transformation of amorphous silica to cristobalite under thermal treatment was investigated by a variety of methods including X-ray diffraction, electron microscopy, and Fourier transform infrared spectroscopy. Results show that amorphous silica on a bacterial cell surface exhibits a direct phase transformation to cristobalite structure at a relatively low temperature (800 C). The surface charge of the bacterial cells does not affect the phase transformation. Three Gramnegative bacteria and three Gram-positive bacteria have been tested in the present study. All these bacteria have been found to facilitate the phase transition of amorphous silica into cristobalite. The observation of amorphous silica transformation on bacterial surfaces to cristobalite highlights the use of bacteria in the synthesis and structure control of silica minerals.
A new multi-cationic polyoxometalate-based hybrid is developed as a recyclable, efficient heterogeneous catalyst for H2O2-mediated oxidation of cyclohexane.
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