Reversible and selective ammonia capture by a layered Co(II) coordination polymer with dense carboxyl pendants

Reversible adsorption and selective separation of ammonia (NH 3 ) is a win–win strategy for resource utilization and pollutant control. However, synchronously achieving the efficiency, selectivity and recyclability for ammonia capture is a technological challenge. Adsorbents developed for such process should be engendered with multiple moderate interactions and structural stability. Here, we present a two-dimensional (2D) coordination polymer (CP) [Co(HAIPA) 2 ] n (Co-AIPA, H 2 AIPA = 5-aminoisophthalic acid) with copious carboxyl groups within the interlayer, which shows a high uptake of 12.1 mmol g −1 at 298 K and 1 bar, exceptionally high selectivity for NH 3 /N 2 (23985) and NH 3 /CO 2 (2394), and cycling durability. It is unveiled that the host–guest interactions between –COOH and NH 3 , and the guest–guest interactions between NH 3 molecules are formed in the slits of Co-AIPA. Overall, the spatial arrangement of dense carboxyl pendants within the interlayer allows for concerted interactions by multiple hydrogen bonding, leading to the superior NH 3 uptake capacity, ideal selectivity, and good regeneration.