Covalent organic frameworks (COFs) have developed as efficient and selective adsorbents to mitigate 99TcO4 - contamination. However, the eco-friendly and scalable production of COF-based adsorbents for the removal of 99TcO4 - has not yet been reported. This study explores the potential of a cationic COF (TpDB-COF) synthesized via a green hydrothermal method, achieving gram-scale yields per batch, thereby addressing a significant limitation of existing COF production methods. The TpDB-COF demonstrates an exceptional stability in strongly acidic conditions (2 weeks in 3 M HNO3), as well as in various organic solvents, making it suitable for harsh nuclear waste environments. Adsorption experiments using ReO4 - as a surrogate for 99TcO4 - show rapid adsorption kinetics, reaching nearly 100% removal efficiency within 1 min (with initial concentration of 28 ppm at a solid-to-liquid ratio of 1 g L-1), a maximum adsorption capacity of 570 mg g-1 and excellent stability. Moreover, the COF maintains high selectivity for ReO4 - even in the presence of competing anions such as SO4 2- and NO3 -. These findings highlight that the hydrothermal synthesis is an effective method to synthesize COF adsorbents for efficient removal of 99TcO4 - and offers a sustainable approach for practical applications.
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