Assembly of a core–shell MOF with stability into polyacrylamide hydrogel for boosting extraction of uranium from seawater

Efficient and selective extraction of uranium (U(VI)) from seawater is essential for sustainable nuclear power production. This study reports a novel adsorbent zeolitic imidazolate framework (ZIF)-67@SiO₂-A/polyacrylamide (PAM) which was synthesized by grafting the core–shell metal–organic frameworks (MOFs)-based nanostructures coated with the 3-aminopropyl triethoxysilane (APTES) functionalized SiO₂ (SiO₂-A) onto PAM hydrogel. The SiO₂ shell was grown on the surface of MOF, which improved the acid-base resistance of MOF. The introduction of ZIF-67@SiO₂-A enhances the specific surface area and adsorption efficiency of the PAM. The ZIF-67@SiO₂-A/PAM shows remarkable adsorption capacity, fast adsorption kinetics, and good reusability for uranium. It has excellent adsorption property (6.33 mg·g⁻¹, 30 d) in natural seawater. The X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), energy dispersive spectroscopy (EDS) mappings, and density functional theory reveal that the coordination by N and O in ZIF-67@SiO₂-A/PAM with uranium is the main mechanism of uranium adsorption. Thus, ZIF-67@SiO₂-A/PAM has great potential to capture uranium from natural seawater.