Ultrafast and Selective Adsorption of ⁹⁹ TcO ₄ – /ReO ₄ – from Water by Nonporous Cationic Metal–Organic Framework

Rationally designing adsorbents for the effective and selective removal of ⁹⁹TcO₄⁻ from a water environment is extremely desired but remains a challenge. In this study, we successfully constructed a nonporous cationic metal-organic framework (MOF-1) with a three-dimensional architecture. Remarkably, nonporous MOF-1 exhibits extremely fast adsorption kinetics toward ReO₄⁻ (a nonradioactive analog for ⁹⁹TcO₄⁻), achieving adsorption equilibrium within 1 min. And the maximum adsorption capacity of MOF-1 for ReO₄⁻ is 375 mg/g. Furthermore, MOF-1 exhibits exceptional selectivity for ReO₄⁻ removal in the presence of large excesses of competing anions such as NO₃⁻, SO₄²⁻, and Cl⁻, as even 6000 times of SO₄²⁻ in excess does not significantly affect the sorption of ReO₄⁻. Additionally, MOF-1 shows excellent ReO₄⁻ removal efficiency over a broad pH range (2.0-11.0), and it can still remove 97% of ReO₄⁻ after four recycles. Furthermore, a combination of characterization analyses, molecular dynamics simulations, and density functional theory calculations is utilized to clearly elucidate the adsorption mechanism of MOF-1 toward ⁹⁹TcO₄⁻/ReO₄⁻. MOF-1 holds superior adsorption performance and significant potential for large-scale preparation and is proven to be a highly promising material for removing ⁹⁹Tc from contaminated water sources.