High Ammonia Uptake of a Metal–Organic Framework Adsorbent in a Wide Pressure Range

Although numerous porous adsorbents have been investigated for NH₃ capture applications, these materials often exhibit insufficient NH₃ uptake, low NH₃ affinity at the ppm level, and poor chemical stability against wet NH₃ conditions. The NH₃ capture properties of M₂ (dobpdc) complexes (M=Mg²⁺ , Mn²⁺ , Co²⁺ , Ni²⁺ , and Zn²⁺ ; dobpdc⁴⁻ =4,4-dioxidobiphenyl-3,3-dicarboxylate) that contain open metal sites is presented. The NH₃ uptake of Mg₂ (dobpdc) at 298 K was 23.9 mmol g⁻¹ at 1 bar and 8.25 mmol g⁻¹ at 570 ppm, which are record high capacities at both pressures among existing porous adsorbents. The structural stability of Mg₂ (dobpdc) upon exposure to wet NH₃ was superior to that of the other M₂ (dobpdc) and the frameworks tested. Overall, these results demonstrate that Mg₂ (dobpdc) is a recyclable compound that exhibits significant NH₃ affinity and capacity, making it a promising candidate for real-world NH₃ -capture applications.