A triazine-tri-imidazole based cationic covalent organic polymer featuring high recyclability and radiation tolerance for efficient Re(Tc)O4- sequestration

The extraction of TcO 4 - from nuclear wastewater via adsorption-based methods is recognized as a highly promising strategy but confronted with significant challenges due to the harsh conditions often encountered, such as highly acidic or alkaline environments, elevated ionic strengths, and intense radiation fields. In this work, we have designed and synthesized a triazine-tri-imidazole based cationic covalent organic polymer, CTFT, with covalent triazine frameworks (CTF) as the structural building blocks and tri-imidazole-based (TIB) units as the connecting motifs. This highly conjugated polymer successfully overcomes the aforementioned challenges and exhibits remarkable ReO 4 - (a non-radioactive substitute to TcO 4 - ) uptake capabilities across five critical performance metrics simultaneously: ultrafast adsorption kinetics (equilibrium reached within 0.5 min), exceptional resistance to strong acids and bases (4 M HNO 3 and 4 M NaOH), high selectivity towards ReO 4 - (80.5 %, 5000 × over SO 4 2- ), superior radiation resistance (400 kGy γ-rays), and outstanding recyclability (20 cycles, 95.6 % retention). Additionally, CTFT achieves a high ReO 4 - removal efficiency in simulated Hanford waste (85.3 %, 10 g/L). Experimental and theoretical calculation results demonstrate that strong electrostatic interactions and affinity exist between imidazolium cation and ReO 4 - . This finding provides a potential design strategy for developing polymers with high durability in the field of nuclear environmental remediation.