Synthesis of titanosilicate nanoparticles with high titanium content from a silsesquioxane-based precursor for a model epoxidation reaction.

In conventional hydrothermal synthesis of porous titanosilicate materials, undesired aggregation of TiO2 species during the synthesis limits the content of active four-coordinated Ti to an Si/Ti ratio of about 40. Aiming to increase the content of active four-coordinated Ti species, we report a bottom-up synthesis of titanosilicate nanoparticles using a Ti-incorporated cubic silsesquioxane cage as a precursor, which allowed incorporating a larger number of four-coordinated Ti species in the silica matrix to reach an Si/Ti ratio of 19. Even at this relatively high Ti concentration, the catalytic activity in the epoxidation of cyclohexene over the titanosilicate nanoparticles was comparable to that of a conventional reference Ti catalyst, Ti-MCM-41, with an Si/Ti ratio of 60. The activity per Ti site was not affected by the Ti content in the nanoparticles, suggesting that well dispersed and stabilized Ti species were the active sites.

Synthesis of Carbon Nanoparticles with Cobalt-Rich Shell via Pyrolysis of Zn-ZIF@Co/Zn-ZIF: Relevance of Co(III) Precursors.

To the best of our knowledge, this is the first report on the rapid one-pot synthesis of a unique core-shell-structured zeolitic imidazolate framework (ZIF) using Co(III) and Zn(II) precursors. The key to obtaining this unique structure is the use of a Co(III) precursor as the starting material. Transmission electron microscopy (TEM) reveals that Co was present within a 30-nm-thick shell layer of the ZIF material. Thermal decomposition of the ZIF material affords core-shell-structured carbon nanoparticles that have Co on the external surface of the carbon grain. We have previously demonstrated that this carbonaceous material obtained by thermal decomposition exhibited high performance as an adsorbent for nitric oxide, even in the presence of excess oxygen and water vapor, and therefore, it was a suitable material for NOx elimination at low temperatures. The growth mechanism of the synthesized ZIF particles and the differences between synthesized ZIF and conventional Co(II)-ZIF-67 are discussed. The reactivity of the Co(III) precursor is much lower than that of the Co(II) species, leading to slower precipitation of Co(III) than that of Zn(II), thus forming the core-shell structure.

High NH3-SCR reaction rate with low dependence on O2 partial pressure over Al-rich Cu-*BEA zeolite.

Dependence of NH3-SCR reaction rate on O2 partial pressure was investigated at 473 K over Cu ion-exchanged MOR, MFI, CHA and *BEA zeolites with varying "Cu density in micropores". Among the zeolites, Cu-*BEA zeolite demonstrated promising potential as an effective catalyst for NH3-SCR over a wide range of O2 partial pressure.

Synthesis of zeolites using highly amphiphilic cations as organic structure-directing agents by hydrothermal treatment of a dense silicate gel.

Silicalite-1 and siliceous *MRE zeolite were synthesized with a series of highly amphiphilic ammonium cations as organic SDAs. The relationship between the framework type and the chain length of the amphiphilic cation is explained in terms of the intermolecular N-N distance of the elongated SDA.

Porous siloxane-organic hybrid with ultrahigh surface area through simultaneous polymerization-destruction of functionalized cubic siloxane cages.

A novel hierarchically porous, hyper-cross-linked siloxane-organic hybrid (PSN-5) has been synthesized by Friedel-Crafts self-condensation of benzyl chloride-terminated double-four-ring cubic siloxane cages as a singular molecular precursor. Simultaneous polymerization of the organic functional groups and destruction of the siloxane cages during synthesis yielded PSN-5, which has an ultrahigh BET surface area (∼2500 m(2) g(-1)) and large pore volume (∼3.3 cm(3) g(-1)) that to our knowledge are the highest values reported for siloxane-based materials. PSN-5 also shows a high H(2) uptake of 1.25 wt % at 77 K and 760 Torr.

Silica sodalite without occluded organic matters by topotactic conversion of lamellar precursor.

Novel pure silica sodalite with hollow sodalite-cages has been synthesized for the first time by topotactic conversion of layered silicate (RUB-15) precursor. This success has been achieved by stepwise syntheses from silicate monomers, through clusters and layers, to microporous crystals. The pretreatment of layered silicate with small carboxylic acids before conversion is a crucial step. The obtained sodalite possesses accessible micropores, as confirmed by physical adsorption of hydrogen molecules. This plate-like silica sodalite would be very promising as fillers in mixed-matrix membranes for hydrogen separation.