Porous acid-base hybrid polymers for enhanced NH 3 uptake with assistance from cooperative hydrogen bonds.

Carboxylic acid-modified materials are a common means of achieving efficient NH 3 adsorption. In this study, we report that improved NH 3 adsorption capacity and easier desorption can be achieved through the introduction of substances containing Lewis basic groups into carboxylic acid-modified materials. Easily synthesized mesoporous acid-base hybrid polymers were constructed with polymers rich in carboxylic acid and Lewis base moieties through cooperative hydrogen bonding interactions (CHBs). The hybrid polymer PAA-P4VP presented higher NH 3 capacity (18.2 mmol g -1 at 298 K and 1 bar NH 3 pressure) than PAA (6.0 mmol g -1 ) through the acid-base reaction and the assistance from CHBs with NH 3 , while the NH 3 desorption from PAA-P4VP was easier for the reformation of CHBs. Based on the introduction of CHBs, a series of mesoporous acid-base hybrid polymers was synthesized with NH 3 adsorption capacity of 15.8-19.3 mmol g -1 and high selectivity of NH 3 over CO 2 ( S NH 3 /CO 2 = 25.4-56.3) and N 2 ( S NH 3 /N 2 = 254-1068), and the possible co-existing gases, such as SO 2 , had a lower effect on NH 3 uptake by hybrid polymers. Overall, the hybrid polymers present efficient NH 3 adsorption owing to the abundant acidic moieties and CHBs, while the concomitant Lewis bases promote NH 3 desorption.