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

Abstract

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 M-2(dobpdc) complexes (M=Mg2+, Mn2+, Co2+, Ni2+, and Zn2+; dobpdc(4-)=4,4-dioxidobiphenyl-3,3-dicarboxylate) that contain open metal sites is presented. The NH3 uptake of Mg-2(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 Mg-2(dobpdc) upon exposure to wet NH3 was superior to that of the other M-2(dobpdc) and the frameworks tested. Overall, these results demonstrate that Mg-2(dobpdc) is a recyclable compound that exhibits significant NH3 affinity and capacity, making it a promising candidate for real-world NH3-capture applications.