Carbon materials have been prepared using zeolite 13X or zeolite Y as template and acetonitrile or ethylene as carbon source via chemical vapor deposition (CVD) at 550-1000 degrees C. Materials obtained from acetonitrile at 750-850 degrees C (zeolite 13X) or 750-900 degrees C (zeolite Y) have high surface area (1170-1920 m(2)/g), high pore volume (0.75-1.4 cm(3) g(-1)), and exhibit some structural ordering replicated from the zeolite templates. Templating with zeolite Y generally results in materials with higher surface area. High CVD temperature (> or =900 degrees C) results in low surface area materials that have significant proportions of graphitic carbon and no zeolite-type structural ordering. The nitrogen content of the samples derived from acetonitrile varies between 5 and 8 wt %. When ethylene is used as a carbon precursor, high surface area (800-1300 m(2)/g) materials are only obtained at lower CVD temperature (550-750 degrees C). The ethylene-derived carbons retain some zeolite-type pore channel ordering but also exhibit significant levels of graphitization even at low CVD temperature. In general, the carbon materials retain the particle morphology of the zeolite templates, with solid-core particles obtained at 750-850 degrees C while hollow shells are generated at higher CVD temperature (> or =900 degrees C). We observed hydrogen uptake of up to 4.5 wt % and 45 g H(2)/L (volumetric density) at -196 degrees C and 20 bar for the carbon materials. The hydrogen uptake was found to be dependent on surface area and was therefore influenced by the choice of zeolite template and carbon source. Zeolite Y-templated N-doped carbons had the highest hydrogen uptake capacity. Gravimetric and volumetric methods gave similar uptake capacity at 1 bar (i.e., 1.6 and 2.0 wt % for zeolite 13X and Y-templated N-doped carbons, respectively). Our findings show that zeolite-templated carbons are attractive for hydrogen storage and highlight the potential benefits of functionalization (nitrogen-doping).

A combined experimental and theoretical study is presented of several ligand addition reactions of the triplet fragments (3)Fe(CO)(4) and (3)Fe(CO)(3) formed upon photolysis of Fe(CO)(5). Experimental data are provided for reactions in liquid n-heptane and in supercritical Xe (scXe) and Ar (scAr). Measurement of the temperature dependence of the rate of decay of (3)Fe(CO)(4) to produce (1)Fe(CO)(4)L (L = heptane or Xe) shows that these reactions have significant activation energies of 5.2 (+/-0.2) and 7.1 (+/-0.5) kcal mol(-1) respectively. Nonadiabatic transition state theory is used to predict rate constants for ligand addition, based on density functional theory calculations of singlet and triplet potential energy surfaces. On the basis of these results a new mechanism (spin-crossover followed by ligand addition) is proposed for these spin forbidden reactions that gives good agreement with the new experimental results as well as with earlier gas-phase measurements of some addition rate constants. The theoretical work accounts for the different reaction order observed in the gas phase and in some condensed phase experiments. The reaction of (3)Fe(CO)(4) with H(2) cannot be easily probed in n-heptane since conversion to (1)Fe(CO)(4)(heptane) dominates. scAr doped with H(2) provides a unique environment to monitor this reaction--Ar cannot be added to form (1)Fe(CO)(4)Ar, and H(2) addition is observed instead. Again theory accounts for the reactivity and also explains the difference between the very small activation energy measured for H(2) addition in the gas phase (Wang, W. et al. J. Am. Chem. Soc. 1996, 118, 8654) and the larger values obtained here for heptane and Xe addition in solution.

Metal-organic frameworks, typically built by bridging metal centres with organic linkers, have recently shown great promise for a wide variety of applications, including gas separation and drug delivery. Here, we have used them as a scaffold to probe the photophysical and photochemical properties of metal-diimine complexes. We have immobilized a M(diimine)(CO)(3)X moiety (where M is Re or Mn, and X can be Cl or Br) by using it as the linker of a metal-organic framework, with Mn(II) cations acting as nodes. Time-resolved infrared measurements showed that the initial excited state formed on ultraviolet irradiation of the rhenium-based metal-organic framework was characteristic of an intra-ligand state, rather than the metal-ligand charge transfer state typically observed in solution, and revealed that the metal-diimine complexes rearranged from the fac- to mer-isomer in the crystalline solid state. This approach also enabled characterization of the photoactivity of Mn(diimine)(CO)(3)Br by single-crystal X-ray diffraction.