Finding on-board hydrogen storage technology that does not require dangerously high pressures and/or cryogenic temperatures has been the focus of a large body of research. Recent DOE target benchmarks limit operating temperatures for hydrogen storage materials to between -40 °C to &lt;100 °C and pressures &lt;100 bar. Transition metal amino borohydrides present a unique, cost effective approach to relatively high capacity hydrogen storage in that they are characterized by lower dehydrogenation temperatures than those exhibited by alkali and alkaline earth metals. However, these are limited due to the impractically high temperatures required for rehydrogenation and incomplete rehydrogenation due to loss of boron and nitrogen in the form of dehydrogenation intermediates and products. These trends are exemplified by a series of multi-dentate amine containing transition metal borohydrides previously reported by this lab. In particular, iron amino-borohydride is found to have increased stability at room temperature relative to Fe(BH4)2 while still decomposing at temperatures below 100 °C evolving H2 relatively cleanly with a H:M ratio of 7.5. However, this material could not be rehydrogenated at temperatures below 400 °C but rather displayed continued decomposition evolving B2H6 and NH3 gas and forming an amorphous black powder which displays poor H2 physisorption behavior at low temperatures. Here, we have impregnated the Zr-based UiO-66 MOF with FeNB and show modest H2 uptake (0.17 % wt, 70 atm) at 150 °C that is not observed by the FeNB (- 0.13 % wt, 70 atm) or UiO-66 (0.02 % wt, 70 atm) alone. The data presented is the first report, to our knowledge, of low temperature rehydrogenation by a first-row transition metal borohydride.

Hydrogen uptake by an iron amino-borohydride Zr(IV)-metal organic framework hybrid below 300 oC

254th National Meeting (2017)

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