Efficient capture of iodine in steam and water media by hydrogen bond-driven charge transfer complexes

Untreated radioactive iodine (¹²⁹I and ¹³¹I) released from nuclear power plants poses a significant threat to humans and the environment, so the development of materials to capture iodine from water media and steam is critical. Here, we report a charge transfer complex (TCNQ-MA CTC) with abundant nitrogen atoms and π-conjugated system for adsorption of I₂ vapor and I₃^- from aqueous solutions. Due to the synergistic binding mechanism of benzene/triazine rings and N-containing groups with iodine, special I-π and charge transfer interaction can be formed between the guest and the host, and thus efficient removal of I₂ and I₃^- can be realized by TCNQ-MA CTC with the adsorption capacity up to 2.42 g/g and 800 mg/g, respectively. TCNQ-MA CTC can capture 92% of I₃^- within 2.5 min, showing extremely fast kinetics, excellent selectivity and high affinity (K_d = 5.68 × 10⁶ mL/g). Finally, the TCNQ-MA CTC was successfully applied in the removal of iodine from seawater with the efficiency of 93.71%. This work provides new insights in the construction of charge transfer complexes and lays the foundation for its environmental applications.