Pressure-Induced Insertion of Ammonia Borane in the Siliceous Zeolite, Silicalite-1F

Abstract

A combination of Raman spectroscopy and X-ray diffraction was used to investigate the insertion of ammonia borane in the 5.5 Å diameter pores of the hydrophobic, all-silica zeolite, silicalite-1F in the pressure range up to 4.8 GPa. Insertion and nanoconfinement result in the appearance of new Raman modes, especially in the N–H stretching region and significant changes in the intensities and pressure dependencies of a large number of other modes. Orientational disorder of the −BH3 and −NH3 groups persists to higher pressures in nanoconfined as compared to the bulk ammonia borane. The structure of the recovered sample was determined by single crystal X-ray diffraction. Each pore in the unit cell was found to contain between 2 and 3 molecules of ammonia borane forming single-molecule chains due to the spatial constraints. In situ, high pressure, X-ray powder diffraction indicated that the compressibility of the ammonia borane-silicalite-1F composite is three times lower than that of empty silicalite-1F due to pore filling. These results show that silicalite-1F can be a suitable nanoscaffold for this important chemical hydrogen-storage material.

The effect of pressure on open-framework silicates: elastic behaviour and crystal–fluid interaction

“…The re-organization of the intruded molecules in zeolitic hosts, promoted by applied pressure and by other variables (e.g., ultraviolet irradiation, moderate temperature), is one of the most fascinating discovery in material science over the last decade, with potential technological and geological implications. The aforementioned experiments of Santoro et al (2013Santoro et al ( , 2015Santoro et al ( , 2016, Scelta et al (2014), Richard et al (2016), Arletti et al (2015Arletti et al ( , 2017 indicate new routes for creating hybrid host-guest composite materials, where an inorganic framework drives the formation of organic polymer with low dimensionality, acting as a stable host for it. The new hybrid inorganichost/organic-guest materials display completely different physicochemical properties if compared to the parental zeolites, in which the interesting properties imparted by pressure would be retained also at standard conditions, and could be exploited in applications.…”

“…More recently, Richard et al (2016) used a combination of in situ Raman spectroscopy and X-ray diffraction to investigate the P-induced insertion of BNH 6 (ammonia borane, solid at ambient conditions) in the cavities of the hydrophobic silicalite-1F (MFI framework type, Baerlocher et al 2007). A single crystal of silicalite was compressed in a powder of BNH 6 , using a DAC.…”

Supramolecular Organization in Confined Nanospaces

“…This finding was in line with what observed for pure water intrusion in hydrophobic ferrierite by a porosimeter and for pressure‐driven encapsulation of other inorganic species, like ammonia borane. By using Raman spectroscopy, Richard et al . proved that this molecule, solid at normal conditions, could be inserted in hydrophobic silicalite (Figure ) already at pressures of about 0.1 GPa, with a greater orientational disorder of the −BH 3 and −NH 3 groups compared to bulk ammonia borane crystals.…”

“…proved that this molecule, solid at normal conditions, could be inserted in hydrophobic silicalite (Figure ) already at pressures of about 0.1 GPa, with a greater orientational disorder of the −BH 3 and −NH 3 groups compared to bulk ammonia borane crystals. X‐ray diffraction analysis on the composite evidenced the formation of ammonia borane chains due to the spatial constraints, suggesting that each pore in the unit cell should contain between 2 and 3 guest molecules …”

Pressure-induced structural changes in Methylamine borane and dimethylamine borane

“…It is known that thermal decomposition results in the release of hydrogen in several steps between 100-500 ˚C [24]. Infusion of NH 3 BH 3 in mesoporous silica, carbon cryogel, and metal-organic frameworks was found to increase the dehydrogenation kinetics and also to suppress borazine formation (a toxic by-product) [25][26][27][28][29]. Dissociation of NH 3 BH 3 is also reported to be activated by the addition of cation exchange resins, zeolites and ionic liquids [30][31][32].…”