N-substituted amine-borane ionic liquids as fluid phase, hydrogen storage materials

Abstract

A selection of task specific N-substituted amine-borane ionic liquids (N-ABILs) were synthesized in good yield using silyl protecting groups with the aim of developing hydrogen (H₂) storing fuels for automotive applications. A new anhydrous anion exchange method, based on trimethylsilyl reagents, was employed so sensitive pendant functionalities like borane could be incorporated. Controlled thermoylsis of N-ABILs indicate members of this class may be liquids pre- and post-dehydrogenation, joining a relatively small population of putative H₂ storing fuels that can be readily loaded/unloaded from a vehicle. N-ABILs were also blended with ammonia-borane to improve overall H₂ capacity, in one case by ∼2.5×. The products of thermolysis consist of co-oligomerized BN species and highly pure (<1% impurity) H₂ gas.