Magnetic metal-organic frameworks/carbon dots as a multifunctional platform for detection and removal of uranium

Abstract Herein, a design of multifunctional hybrid adsorbent made of a magnetic core and a zeolite imidazolate framework (ZIF-8) shell embedded with carbon dots (CDs) is synthesized to combine detection with separation and recycling of uranium from aqueous solution. The adsorbents retain the strong superparamagnetic behavior of Fe 3 O 4 nanoparticles and similar luminescence of carbon dots. Interestingly, the adsorbents not only exhibit obviously fluorescence response for U (VI) but also enhance U (VI) adsorption performance via assisting with the loaded‑carbon dots. The adsorption processes of U(VI) on Fe 3 O 4 -CMC@ZIF-8 and Fe 3 O 4 -CMC@ZIF-8@CDs well fit with the pseudo-second-order model. The maximum U(VI) adsorption amount of Fe 3 O 4 -CMC@ZIF-8@CDs is high as 606.06 mg/g at pH = 4.0 and T  = 298 K with Langmuir model, which is obviously higher than that of Fe 3 O 4 -CMC@ZIF-8 (564.97 mg/g). Particularly, BET, FTIR and XPS results show that the improvement of adsorption properties on Fe 3 O 4 -CMC@ZIF-8@CDs is mainly ascribed to the large specific surface area and abundant nitrogen/oxygen functional groups on the surface, suggesting that the main interaction mechanisms are diffusion and coordination. The design for hybrid materials provides a convenient way to achieve a multifunctional adsorbent with detection, separation and recycling properties for uranium.