Dehydrogenation tuning of ammine borohydrides using double-metal cations

The strategy of using double-cations to tune the temperature and purity of dehydrogenation of ammine borohydrides is reported. The first double-cation ammine borohydride, Li(2)Al(BH(4))(5)·6NH(3), which forms a novel structure with ordered arrangement of Al(NH(3))(6)(3+) ammine complexes and Li(2)(BH(4))(5)(3-) complex anions, is found to release over 10.0 wt % hydrogen below 120 °C with favorable kinetics and high H-purity (>99%).