H 3 PW 12 O 40 /MIL-88A(Fe)/MIL-88B(Fe)/NiFe 2 O 4 nanocomposite: A new magnetic sorbent based on MOF/MOF hybrid coupled with PW 12 O 40 3- polyanions for efficient removal of hazardous antibiotics and dyes from water

In this research, a new magnetic quaternary sorbent based on the MOF-on-MOF approach was synthesized through a solvothermal method. For this purpose, the MIL-88A(Fe)/MIL-88B(Fe) binary metal–organic frameworks (biMOFs) were prepared, and H 3 PW 12 O 40 polyoxometalate and nickel ferrite (NiFe 2 O 4 ) were incorporated into this MOF/MOF hybrid. The as-prepared magnetically recyclable {H 3 PW 12 O 40 }/MIL-88A(Fe)/MIL-88B(Fe)/NFO nanocomposite was characterized by FT-IR spectroscopy, Raman spectroscopy, powder X-ray diffraction (XRD), SEM, EDX, TEM, BET surface area, zeta potential, and magnetic measurements. The composite displayed high adsorption capabilities and was effective in separating tetracycline (TC) and ciprofloxacin (CIP) antibiotics, as well as removing organic dyes from water solutions. The impacts of factors such as dosage, temperature, initial concentration, and pH on the absorption process were analyzed. The outcomes suggested that the nanocomposite adsorbed 100 % of drugs in 14 min for TC and 20 min for CIP from water with a maximum adsorption capacity of 1428.57 mg g-1 and 344.82 mg g-1, respectively. It is capable of selectively adsorbing cationic methylene blue (MB) dye in 100 % within a few minutes, even in mixtures.The nanocomposite's enhanced electrostatic attraction plays a significant role in its improved absorption rates and capacities. The adsorption process fits well with the Freundlich isotherm model and pseudo-second-order adsorption kinetic model, demonstrating a multilayer adsorption and chemical adsorption behavior. The nanocomposite exhibits stability and recyclability without any structural changes, making it a highly promising adsorbent for effectively removing drugs and organic dyes from polluted water.