A record ammonia adsorption by calcium chloride confined in covalent organic frameworks

Ammonia is a vital chemical raw material, but it is also a highly toxic environmenal pollutant. However, its highly efficient uptake and reversible release is a challenge. Herein, we have designed and synthesized a series of hybrid materials for efficient NH₃ capture by confining calcium chloride (CaCl₂) in a porous covalent organic framework (COF). A high capture capacity of 26.5 mmol g^-1 is obtained at 25 °C and 1 bar, which is the highest value among existing porous materials, and NH₃ can be easily desorbed at 80 °C under vacuum for 2 h. Particularly, the hybrid COF is highly efficient for the absorption of low NH₃ content. Such excellent performance is ascribed to the highly dispersion of CaCl₂ in the pores of the COF, and coordinating interaction of NH₃ to Ca²⁺ together with hydrogen bond interaction between NH₃ and Cl^-.