Green synthesis of amorphous Ce-MOFs as efficient adsorbents towards Ofloxacin antibiotics

This study presents an efficient and green strategy for the synthesis of amorphous metal-organic frameworks (MOFs). Hence, we synthesized a series of cerium (Ce)-based amorphous MOFs at room temperature using water as the sole solvent via screening the undissolved organic ligands. XRD and ATR-FTIR analyses confirmed the highly amorphous nature and preserved chemical structure of the synthesized Ce-MOFs, while N2 adsorption/desorption and TGA results revealed mesoporosity and good thermal stability. The synthesized small-sized amorphous Ce-MOFs particles exhibited hierarchical pores in the range of 4–15 nm, moderate surface areas (up to 280 m2/g), large pore volumes (up to 0.54 cm3/g), abundant active adsorption sites, and good structural stability, which are all beneficial for the efficient removal of the Ofloxacin (OFL) antibiotic from water. Among different synthesized amorphous Ce-MOFs, the Ce-MOF-A-2 with a surface area of 152 m2/g showed a high affinity toward OFL molecules, resulting in the highest experimental adsorption capacity of 138.98 mg/g under optimal conditions (T = 298 K, t = 4 h, pH ≈ 8). The experimental adsorption data for this adsorbent followed the Langmuir isotherm and pseudo-second-order kinetic models, resulting in a maximum calculated adsorption capacity of 140.84 mg/g, higher than its crystalline counterpart. Additionally, this amorphous adsorbent showed satisfactory regeneration and reusability performances, making it an acceptable adsorbent for water decontamination.