Observation of an Intermediate to H Binding in a Metal-Organic Framework.

Coordinatively unsaturated metal sites within certain zeolites and metal-organic frameworks can strongly adsorb a wide array of substrates. While many classical examples involve electron-poor metal cations that interact with adsorbates largely through physical interactions, unsaturated electron-rich metal centers housed within porous frameworks can often chemisorb guests amenable to redox activity or covalent bond formation. Despite the promise that materials bearing such sites hold in addressing myriad challenges in gas separations and storage, very few studies have directly interrogated mechanisms of chemisorption at open metal sites within porous frameworks.

Thermal Conversion of Unsolvated Mg(BH) to BH in the Presence of MgH.

In the search for energy storage materials, metal octahydrotriborates, M(BH) , = 1 and 2, are promising candidates for applications such as stationary hydrogen storage and all-solid-state batteries. Therefore, we studied the thermal conversion of unsolvated Mg(BH) to BH as-synthesized and in the presence of MgH. The conversion of our unsolvated Mg(BH) starts at ∼100 °C and yields ∼22 wt % of BH along with the formation of (closo-hydro)borates and volatile boranes.

Heterolytic Scission of Hydrogen Within a Crystalline Frustrated Lewis Pair.

We report the heterolysis of molecular hydrogen under ambient conditions by the crystalline frustrated Lewis pair (FLP) 1-{2-[bis(pentafluorophenyl)boryl]phenyl}-2,2,6,6-tetramethylpiperidine (KCAT). The gas-solid reaction provides an approach to prepare the solvent-free, polycrystalline ion pair KCATH2 through a single crystal to single crystal transformation. The crystal lattice of KCATH2 increases in size relative to the parent KCAT by approximately 2%.

Kinetic Enhancement of Direct Hydrogenation of MgB to Mg(BH ) upon Mechanical Milling with THF, MgH , and/or Mg.

Modification of magnesium diboride, MgB , by mechanical milling with THF, MgH , and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH ) , by 300 bar and 100 °C. Following mechanical milling with MgH or THF and Mg, MgB can be hydrogenated to Mg(BH ) at 300 °C under 700 bar of H while achieving ∼54-71 % conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH ) and MgB .