Ti-substituted boranes as hydrogen storage materials: a computational quest for the ideal combination of stable electronic structure and optimal hydrogen uptake.

Based on the Wade-Mingos n+1 rule for the closo-boranes (B(n)H(n) (2-)), a family of Ti-substituted closo-boranes has been designed computationally. Due to the isolobal relation of Ti to a BH(2-) group, these Ti-substituted boranes have n+1 pairs of skeletal electrons to fulfill the bonding requirement for such stable cages. The reported representatives, B(4)H(4)Ti(2)H(2) in particular, not only have stable electronic structures but also superior capability to adsorb hydrogen. The optimal binding energies and high gravimetric densities of hydrogen storage indicate their potential to store hydrogen for practical applications. Simultaneously achieving electronic stability and optimal hydrogen uptake may provide a way of overcoming the issue of aggregation in designing transition-metal-decorated hydrogen storage materials. This study invites experimental realization of novel boranes and provides new ideas for searching for hydrogen storage materials.