Cationic covalent organic polymers based on guanidine with higher positive potential for selective sorption of ReO4−: Synthesis and DFT calculation

Removal of TcO 4 − from liquid radioactive waste is urgent due to its long half-life and high mobility. Herein, two guanidine-based cationic covalent organic polymers (TG-TPAL-H and TG-TPAL-OMe) were synthesized, and were used to research for the removal of ReO 4 − . TG-TPAL-H showed high removal efficiency, its sorption capacity got to 549 mg g −1 and distribution coefficient K d was 1.17 × 10 6  mL g −1 . What impressively, the TG-TPAL-H removed 80% of ReO 4 − even there was 1000 times of competing anions (Cl − , SO 4 2− , H 2 PO 4 − ). While TG-TPAL-OMe showed a poor performance on ReO 4 − with the capacity of 317 mg g −1 and K d of 6.9 × 10 4  mL g −1 . TG-TPAL-H can remove 87% ReO 4 − from simulated Hanford LAW stream sample, while TG-TPAL-OMe just can remove 35%. The difference between the two materials can be attributed to the electron donating group (Methoxy) in TG-TPAL-OMe reduced the positive charge density of guanidine, which was demonstrated by the ESP of density functional theory (DFT) calculation.