Hydrogen-rich materials infused in nanoscaffolds offer a promising approach to on-board hydrogen storage. A mesoporous scaffold decreases the temperature for hydrogen release from ammonia borane (AB), a conventional hydrogen-storage material, to below 80 °C and leads to an increase in the purity of the hydrogen released. (See schematic representation of a hydrogen-bonded AB network in the cross-section of a single pore.) <!--EMPTY SOURCE-->

The mechanism of hydrogen release from solid state ammonia borane (AB) has been investigated via in situ solid state ¹¹B and ¹¹B{¹H} MAS-NMR techniques in external fields of 7.1 T and 18.8 T at a decomposition temperature of 88 °C, well below the reported melting point. The decomposition of AB is well described by an induction, nucleation and growth mechanistic pathway. During the induction period, little hydrogen is released from AB; however, a new species identified as a mobile phase of AB is observed in the ¹¹B NMR spectra. Subsequent to induction, at reaction times when hydrogen is initially being released, three additional species are observed: the diammoniate of diborane (DADB), [(NH₃)₂BH₂]⁺[BH₄]⁻, and two BH₂N₂ species believed to be the linear (NH₃BH₂NH₂BH₃) and cyclic dimer (NH₂BH₂)₂ of aminoborane. At longer reaction times the sharper features are replaced by broad, structureless peaks of a complex polymeric aminoborane (PAB) containing both BH₂N₂ and BHN₃ species. The following mechanistic model for the induction, nucleation and growth for AB decomposition leading to formation of hydrogen is proposed: (i) an induction period that yields a mobile phase of AB caused by disruption of the dihydrogen bonds; (ii) nucleation that yields reactive DADB from the mobile AB; and (iii) growth that includes a bimolecular reaction between DADB and AB to release the stored hydrogen.

The strong efforts devoted to the exploration of BNH compounds for hydrogen storage have led to impressive advances in the field of boron chemistry. This review summarizes progress in this field from three aspects. It starts with the most recent developments in using BNH compounds for hydrogen storage, covering NH₃BH₃, B₃H₈ ⁻ containing compounds, and CBN compounds. The following section then highlights interesting applications of BNH compounds in hydrogenation and catalysis. The last part is focused on breakthroughs in the syntheses and discovery of new BNH organic analogues. The role of N–H^δ+⋯H^δ−–B dihydrogen interactions in molecule packing, thermal hydrogen evolution, and syntheses is also discussed within the review.

A new synthetic procedure to make the condensed phase hydrogen storage material, ammonia borane (NH₃BH₃, abbreviated as AB), is described and compared with previous literature procedures. Ammonia borane with a gravimetric density ca. 194 gm H₂ kg⁻¹ and a volumetric density ca. 146 H₂ litre⁻¹, is a promising chemical hydrogen storage material for fuel cell powered applications. The work shows that ammonium borohydride, NH₄BH₄, formed in situ by the metathesis of NH₄X and MBH₄ salts (M = Na, Li; X = Cl, F) in liquid NH₃, can be induced to decompose in an organic ether to yield AB in near quantitative yield. The purity of the AB prepared by this one-pot synthetic strategy is sufficient to meet the thermal stability requirements for on-board hydrogen storage.