MXene/Cu0 fabricated via green molten salt etching: Cu0Ti dual active sites for synergistic radioactive iodine sequestration

Volatile radioactive iodine from the nuclear industry poses persistent safety risks, thus making it critical to develop adsorbents for efficient capture of elemental iodine in both gaseous and liquid phases. Ti 3 C 2 T x MXene is a promising environmental adsorbent, but its iodine adsorption performance is limited by scarce intrinsic high-activity metal sites. Existing MXene-based adsorbents mostly rely on fluorine-containing etching or silver loading, suffering from fluorine toxicity and potential biotoxicity. Most only focus on single-phase adsorption, and few study their adsorption performance in both gas and liquid phases. The atomic-level synergistic mechanism remains unclear. In this work, a green Lewis acid molten salt etching method was used to prepare highly dispersed Cu 0 -loaded MXene via one-step in situ synthesis, using copper chloride as both etchant and copper source. Notably, a fluorine-free in-situ etched Cu-based MXene is developed herein and applied to elemental iodine capture in both gaseous and liquid phases. Its adsorption capacities reached 1525.33 mg·g −1 (liquid, 45 °C) and 1190 mg·g −1 (gas, 200 °C), outperforming Ti 3 AlC 2 precursor, pristine MXene and most reported modified MXene materials and commercial silver-loaded zeolites. Dynamic breakthrough tests yield a saturation capacity of 726 mg·g −1 under 150 ppmv iodine vapor (20 sccm), with 582 mg·g −1 retained under 400 ppmv CO 2 competition. For 150 °C static gaseous adsorption, the adsorbent maintains 83.22% of its initial capacity after 5 regeneration cycles and 72.65% after 6 cycles via sodium borohydride elution. Systematic characterizations and DFT calculations confirmed efficient iodine immobilization via a physicochemical synergistic mechanism: chemisorption dominated by Cu 0 Ti dual active sites forming stable CuI and Ti I bonds, supplemented by interlayer physisorption. This work provides new insights into the green design of high-performance iodine adsorbents and atomic-level mechanism elucidation.