Exceptional High and Reversible Ammonia Uptake by Two Dimension Few-layer BiI₃ Nanosheets

The emission of NH₃ into atmosphere is seriously harmful for human health and public safety, thus the capture and recovery of NH₃ from ammonia emissions is highly desirable. In recent years, many kinds of solid adsorbents have been exploited to absorb NH₃. However, these materials do not show the advantages of high uptake capacity and good recyclability at the same time. Here, nontoxic and low cost few-layer BiI₃ nanosheets have been prepared from bulk BiI₃ powder by a simple and efficient liquid phase exfoliation strategy using green solvents and then applied for the NH₃ capture for the first time. The results show that the adsorption capacity of NH₃ of BiI₃ nanosheets reaches up to 22.6 mmol/g at 1.0 bar and 25 °C, which approaches the record value for NH₃ adsorption. Importantly, the NH₃ uptake in BiI₃ nanosheets is completely reversible and no clear loss in uptake capacity is observed after 10 cycles of adsorption-desorption. Furthermore, the BiI₃ nanosheets exhibit remarkable selectivity for the separation of NH₃/CO₂ at 70 °C with theoretical selectivity coefficient of 700, which is promising for the selective separation of NH₃ and CO₂ in hot tail gas of some industrial processes. Mechanism studies indicate that such superior NH₃ capacity, excellent reversibility and remarkable selectivity are primarily attributed to the Bi³⁺-NH₃ coordination interactions.