Regenerable and stable olefin-linked covalent organic frameworks with coordination template for selective and efficient trapping of scandium ion

Using coordination templates within covalent organic frameworks (COFs) can significantly enhance the selective properties of these materials. Herein, 1,4-phthalaldehyde, 2,4, 6-trimethyl-1,3, 5-triazine, and a scandium coordination complex were selected to perform a three-in-one strategy, and a class of stable olefin-linked covalent organic frameworks with coordination templates were synthesized. By adjusting the proportion of organic ligands to scandium complexes, a range of crystalline COFs with tunable scandium incorporation levels has been obtained. Upon removing scandium from the material with the suitable metal content, we achieved a metalimprinted COF (De-Sc-0.33), demonstrating remarkable affinity and selectivity for Sc3+ ions, even in acidic environments and amidst competing metal ions (53.56 mg/g). In particular, the skeleton benefits from the characteristics of olefins, and its regenerability and stability in highly acidic environments surpass those of existing scandium adsorbents (with a capacity drop of less than 2 % after 20 cycles), thus holding tremendous potential for the enrichment of scandium in practical applications.