Enhanced NH3 uptake and selectivity at low pressure in monolithic MOF-808 metal–organic gels incorporating CuCl2

Abstract

The capture and separation of trace NH₃ from industrial processes or polluted air remains a significant challenge. Herein, we report a monolithic CuCl₂@G808 metal–organic gel achieving an NH₃ uptake of 2.23 mmol g⁻¹ at 298 K and 0.002 bar: a 79% enhancement compared to pristine G808. The ideal adsorbed solution theory (IAST) selectivity reaches 2.8 × 10³ for NH₃/N₂ and 4.9 × 10⁵ for NH₃/H₂ at 298 K, ranking among the highest reported values. In situ FTIR and XPS analyses reveal that the excellent performance mainly originates from two synergistic mechanisms: (i) coordination between NH₃ and Cu²⁺ sites, and (ii) hydrogen bonding between NH₃ and Cl⁻ sites.