Oriented Crystallization of Ammonium Sulfate from Hexagonal Boron Nitride/Sulfuric Acid Intercalation Compounds

Abstract

Controlling crystallization is a long-standing issue both from a fundamental and an applied perspective. In particular, our understanding of the influence of confinement on crystallization is far from complete. In this work, we utilize the confined interlayer spaces of hexagonal boron nitride (h-BN), which is one of the typical two-dimensional layered materials with atomically flat BN sheets, not only to prepare h-BN/H2SO4 intercalation compounds but also to initiate crystallization via the acid/base reaction between the intercalant (H2SO4) and gaseous ammonia. We report that the present acid/base reaction leads to the formation of highly oriented ammonium sulfate crystals along specific crystallographic directions. This oriented crystal growth originates from the 2D crystal nucleated in the confined interlayer spaces of h-BN.

Large-Gap Quantum Spin Hall Insulators in Two-Dimensional Hafnium Halides: Unraveling the Impact of Strain and Substrate

“…From the projected band structures of the heterobilayer in Figure 4(c), we observe that h-BN has a band gap of approximately 4.6 eV, which is consistent with previous DFT studies. 39 Without considering SOC, the conduction and valence bands of HfBr are degenerate at the Γ point and the Fermi level. However, upon introducing SOC, the degeneracy of the energy bands is lifted, leading to a band gap opening of 99 meV.…”

Conversion of Recovered Ammonia and Carbon Dioxide into Urea in the Presence of Catalytically Active Copper Species in Nanospaces of Porous Silica Hollow Spheres

“…For offering a chemical environment to integrate the chemical compounds at high density, we have focused on nanoconfinement techniques in porous solid materials including nanospaces. Porous materials have been reported in various fields, − and unique phenomena that cannot be observed in typical gas and liquid phases have occurred in the nanospaces of the porous materials; − for example, significant increase of gas solubility, ,, significant decrease of the freezing points of solvents, , and so on. It has been suggested that the intrinsic interactions among the confined molecules in nanospaces played an important role in endowing the unique properties of the molecules. ,, We have also reported the intrinsic stability of the adsorbed ammonia molecules in nanospaces of porous hollow spheres of silica-based oxides. − The stability of the confined ammonia molecules in the nanospaces is expected to originate the molecular interactions, especially hydrogen bonding.…”