Creating Cu(I) Sites in an MOF for Reversible Capture of Molecular Iodine at Low Concentrations and High Temperatures

Developing adsorbents for capturing low-concentration molecular iodine (I₂) from nuclear plant off-gases is crucial yet poses significant challenges. Here, we report a specifically designed adsorbent, named MFU-Cu(I), which is prepared by incorporating coordinatively unsaturated monovalent Cu species into an azolate-based MOF. MFU-Cu(I) integrates excellent thermal stability, high porosity, and potent chemical adsorption sites, demonstrating superior I₂ capture performance under stringent conditions. At a low I₂ concentration of 150 ppmv, MFU-Cu(I) achieves high I₂ uptake capacities at both room temperature (3.11 g g^–1) and 150 °C (0.2 g g^–1), making it the most effective I₂ adsorbent to date. The ability of MFU-Cu(I) to capture I₂ at low concentrations and elevated temperatures is attributed to the Cu(I) sites firmly anchored within the MOF framework. These sites facilitate dissociative adsorption of I₂ through a redox reaction, while inhibiting the irreversible formation of CuI precipitates. Consequently, MFU-Cu(I) can be readily regenerated after I₂ adsorption via ion exchange followed by vacuum heating. The regenerability of MFU-Cu(I) represents a notable advantage over other chemical adsorbents developed for I₂ capture.