Direct synthesis of anion exchange polymer threaded in a metal-organic framework through in situ polymerization of an ionic liquid

Abstract

We report one step synthesis of anion exchange polymer threaded in a metal-organic framework (MOF) via in situ polymerization of an ionic liquid (IL) monomer. The ionic liquid 3-methyl-1-vinylimidazolium iodide (3MVIm-I) is water miscible and can be easily impregnated into hydrophilic UiO-66 before triggering in situ polymerization to produce the composite. This simple synthesis does not involve an amination step, which was previously required to incorporate anion-exchange function of a polymer threaded into ZIF-8. This method also avoids difficult impregnation of hydrophobic precursors into hydrophilic MOF for in situ ionic liquid formation and their removal. The synthesized P3MVim-I∼UiO-66 composite is tested for anion exchange and cation rejection in aqueous solvent. P3MVim-I∼UiO-66 demonstrates outstanding ion selectivity over pristine UiO-66 and commercial anion exchange resin (Amberlyst A26). Aside the high OH− exchange capacity (6.05 meq g−1), more than 95% of inorganic anions (AuCl4−) and 90% of anionic organic dye (Acid Blue 9) are exchanged by P3MVim-I∼UiO-66 within 30 min. In addition, there is complete rejection of standalone cationic dye (Rhodamine B) by P3MVim-I∼UiO-66 while the pristine UiO-66 exhibits no rejection. Crystallinity of the UiO-66 host is retained after impregnation and ion exchange.