Stable to surfactant removal by calcination, Ti‐TMS1 is the first hexagonally packed, mesoporous transition metal oxide. The synthesis of this new material was achieved by a modified sol–gel technique from titanium alkoxides and phosphate surfactants. The large internal surface area, narrow and controllable pore size, thermal stability, and variable oxidation states of the metal give this new material great potential as a catalyst and sorbent.

An overview of recent advances in the application of non‐carbonaceous nanostructured and composite materials in hydrogen storage is presented in this review. The main focus is on complex hydrides, non‐graphitic nanotubes, and other porous composite and framework materials, since carbon nanotubes have been the subject of numerous other reviews. Recent advances in the area of alanates show a promising reversible absorption capability of up to 5 %, closing in on the projected Department of Energy (DOE) target of 6 %. Non‐carbon nanotubes mainly showed a sorption capacity of 1–3 wt.‐%, although a promising level of 4.2 wt.‐% is shown by boron nitride nanotubes after collapse of their walls. Other interesting materials included here are lithium nitride and porous metallo‐organic frameworks.

Since the porous structure is completely retained upon surfactant removal, Nb‐TMS1, a hexagonally packed mesoporous transition metal oxide, is an interesting molecular sieve. The synthesis of this material was accomplished by a novel route in which the inorganic precursor 1 and the surfactant 2 were attached by a covalent NbN bond; this bond is probably retained throughout the course of the synthesis. equation image

The synthesis and characterization of Ta-TMS1, a new member of a growing family of hexagonally packed transition-metal oxide mesoporous molecular sieves (termed TMS1) is described. Ta-TMS1 exhibits a hexagonal array of pores which can be varied in size from 20 to 40 Å and surface areas of over 500 m2/g. The thermal and hydrothermal stabilities of Ta-TMS1 are 500 and 450 °C, respectively, making this system the most stable transition-metal oxide molecular sieve yet isolated. The high hydrocarbon adsorption capacities of this material make it a promising candidate as a catalyst support for hydrocarbon re-forming processes. The synthesis of this material was achieved by a novel approach involving the careful hydrolysis of long-chain primary amine complexes of Ta(OEt)5. This ligand-assisted templating mechanism represents a new approach to the synthesis of porous materials in that the inorganic precursor is covalently bonded to the template throughout synthesis. The high thermal stability, ease of synthesis and doping, and high surface areas of this material make it competitive with zeolitic molecular sieve materials and may lead to a wide variety of commercial applications.

A systematic study of the factors governing the formation of Nb-TMS1, a niobium-based mesoporous hexagonally-packed transition metal oxide molecular sieve, is reported. The synthesis of this material was achieved through a novel ligand-assisted liquid crystal templating mechanism in which a discrete covalent bond is used to direct the templating interaction between the organic and inorganic phases. In general, the synthesis of Nb-TMS1 is more strongly affected by starting conditions such as temperature, surfactant-to-metal ratio, pH, and solvent than by temperature and time of aging after the initial hydrolysis step. The results also show that Nb-TMS1 can be synthesized under conditions which strongly disfavor the formation of micelles. This suggests that Nb-TMS1 is formed via a mechanism involving self-assembly with concomitant condensation. It was found that with increasing surfactant-to-metal ratios, new hexagonal P63/mmc (Nb-TMS2) and layered (Nb-TMS4) phases could be formed, while increasing the surfactant chain length led to a new cubic phase (Nb-TMS3). Crystals of Nb-TMS1 of up to several mm in dimensions were also grown. These crystals are larger than the biggest mesoporous crystals reported by a factor of 3 orders of magnitude. These crystals retain their structure on micelle removal by acid treatment and are thus of great interest as hosts for quantum wires.