Self-Repairing [MEDTA]2- functionalized poly(ionic liquid)s in the application of NH3 adsorption through reversible NH3 insertion

MOFs have high adsorption performance of ammonia (NH 3 ) because of its porosity and abundant coordination sites, especially MOFs containing carboxylic acid ligands have emerged as effect NH 3 adsorbents. But, it’s troublous for reversible ammonia adsorption for the strong metal-NH 3 coordination or the collapse of adsorbents. [MEDTA] 2- is a very stable and classic carboxylic acid-containing complex, but there was no relevant report. Therefore, this work carried out the design and synthesis of PVIm-R8-MEDTA based on the use of the coordination structure of [MEDTA] 2- and the stability of PILs’ skeleton. The characterization indicated the [MEDTA] 2- could be introduced into PILs successfully for the hydrogen bonding interactions with the imidazolium cation, and the obtained PVIm-R8-MEDTA presented enhanced NH 3 capacity (10.4–14.7 mmol/g) than their precursor PVIm-R8-Br (7.8 mmol/g). The mechanism of NH 3 adsorption was proposed by DFT calculation, spectroscopic method, and the calorimetric test, it indicated the NH 3 was fixed by imdazolium cation through hydrogen bonding and inserted into two of the carboxylate and metal bonds of [MEDTA] 2- . Because of the multi-meshing coordination of [EDTA] 4- and metal ions, the disconnected carboxylate ions could easily coordinate with metal ions again and repair the chelating structure of [MEDTA] 2- , which caused the ammonia easily be desorbed. In the process of gas adsorption, there was no bonding breakage of the skeleton of PILs, which helped the PVIm-R8-MEDTA be recovered under moisture and NH 3 atmosphere. Thanks for the designability of PILs, such as the cationic structure, structure and size of cross-linking agent, the choice of complex anion and so on, it provides a new design idea and theoretical basis for efficient and reversible ammonia adsorption materials.