Fe-doped Zr-based metal-organic frameworks for efficient bromide ion capture: Adsorption performance and mechanism

The efficient recovery of bromide ions (Br-) from aqueous solutions can alleviate the shortage of bromide re-sources and holds significant practical value. In this work, a Fe-doped Zr-based metal-organic framework (Fe-MOF-808) was successfully prepared, demonstrating remarkable efficacy in the high-capacity adsorption of Br-. The incorporation of Fe leads to reduction in particle size, elevation of specific surface area, and defect-rich structure, allowing Fe-MOF-808 to quickly adsorb Br-, and the adsorption process follows the Langmuir isotherm and pseudo-second-order kinetic model. Notably, under the conditions of an initial Br- concentration of 100 mg/L, 298 K and pH of 7, Fe-MOF-808 demonstrates exceptional adsorption capacity for Br- (247 mg/g), surpassing that of the pristine MOF-808 and the majority of previously reported adsorbents. Additionally, in-sights derived from Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations elucidate the Br- adsorption mechanism on Fe-MOF-808, which can be attributed to the robust interaction between M-OH (M = Zr, Fe) groups and Br-, enhanced electron transfer behavior subsequent to iron modification, and ligand exchange processes. In summary, Fe-MOF-808 emerges as an efficient adsorbent for capturing Br- from aqueous solution, providing a novel approach for the design of advanced Br- adsorbents.