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.
Liu et al. (Wed,) studied this question.