Deep eutectic solvents with multiple weak acid sites for highly efficient, reversible and selective absorption of ammonia

Advanced Materials for NH3 Capture: Interaction Sites and Transport Pathways

Ammonia (NH3) is a carbon-free, hydrogen-rich chemical related to global food safety, clean energy, and environmental protection. As an essential technology for meeting the requirements raised by such issues, NH3 capture has been intensively explored by researchers in both fundamental and applied fields. The four typical methods used are (1) solvent absorption by ionic liquids and their derivatives, (2) adsorption by porous solids, (3) ab-adsorption by porous liquids, and (4) membrane separation. Rooted in the development of advanced materials for NH3 capture, we conducted a coherent review of the design of different materials, mainly in the past 5 years, their interactions with NH3 molecules and construction of transport pathways, as well as the structure-property relationship, with specific examples discussed. Finally, the challenges in current research and future worthwhile directions for NH3 capture materials are proposed.

Porous acid-base hybrid polymers for enhanced NH3 uptake with assistance from cooperative hydrogen bonds

Carboxylic acid-modified materials are a common means of achieving efficient NH3 adsorption. In this study, we report that improved NH3 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 NH3 capacity (18.2 mmol g-1 at 298 K and 1 bar NH3 pressure) than PAA (6.0 mmol g-1) through the acid-base reaction and the assistance from CHBs with NH3, while the NH3 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 NH3 adsorption capacity of 15.8-19.3 mmol g-1 and high selectivity of NH3 over CO2 (SNH3/CO2 = 25.4-56.3) and N2 (SNH3/N2 = 254-1068), and the possible co-existing gases, such as SO2, had a lower effect on NH3 uptake by hybrid polymers. Overall, the hybrid polymers present efficient NH3 adsorption owing to the abundant acidic moieties and CHBs, while the concomitant Lewis bases promote NH3 desorption.

Efficient and reversible absorption of low pressure NH3 by functional type V deep eutectic solvents based on phenol and hydroxypyridine

Highly efficient and reversible absorption of low pressure ammonia by phenol-hydroxypyridine deep eutectic solvents.

Investigation of NH3 absorption by protic imidazolium thiocyanate-based deep eutectic solvents with multiple binding sites and low viscosity

Protic [Im][SCN]-based DESs with multiple binding sites and low viscosity for NH3 capture and separation are reported.