Few-Layered Hexagonal Boron Nitrides as Highly Effective and Stable Solid Adsorbents for Ammonia Separation

Solid adsorbents with high NH3 separation performance and good stability are particularly important for industrial applications. In our work, few-layered hexagonal boron nitrides (h-BNs) were synthesized and proposed as a kind of solid adsorbent by utilizing the abundant Lewis acidic B atoms on h-BNs. The synthesized h-BNs were investigated for NH3 separation both experimentally and theoretically. It is found that the NH3 isotherms of h-BNs slightly deviate from the ideal profiles, suggesting that the h-BNs enable moderate interactions with NH3. At the pressure of 0.1 and 1 bar, the h-BNs can adsorb as much as 2.33 and 8.67 mmol/g of NH3, respectively. The h-BNs also demonstrate highly selective adsorption of NH3 from other gases such as N2, H2, and CO2, regardless of calculated ideal selectivities or breakthrough adsorption of mixed gases. The NH3 adsorption of h-BNs can be completely reversed, and the h-BNs also exhibit high oxidative resistance, which is of vital importance for the long-term application in industry. Density functional theory calculations and molecular dynamics simulations were further conducted to rationalize the effective separation of NH3 by h-BNs and disclose the underlying mechanism at the molecular level.