Room-Temperature Synthesis of Melamine-Based Hydrogen-Bonded Organic Frameworks as Efficient Adsorbents for Ofloxacin Removal

Hydrogen-bonded organic frameworks (HOFs), an emerging type of crystalline porous material, have been proposed as potential adsorbent materials for the removal of pollutants from water. In the present work, by the knowledge of strong interactions between melamine (MA) and cyanuric acid (CA) monomers, MA–CA HOFs were proposed as efficient adsorbents to remove ofloxacin (OFX) antibiotics from water. Hence, a series of MA-based HOFs were synthesized at room temperature using different solvents (e.g., water, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF)) as reaction media and ethanol as an exchange solvent. PXRD, FTIR, FESEM, BET, and zeta potential analyses were applied to perform the characterization of the resulting MA-based HOFs. The results obtained from these analyses reveal the successful synthesis of HOFs with high crystallinity and acceptable porosity in all used solvents. This study reports the room-temperature synthesis of MA-based HOFs in water as the sole solvent, in which the synthesized HOF–Water sample exhibited an acceptable adsorption capacity of 441.43 mg/g toward OFX. However, the sample synthesized in the presence of DMSO (HOF–DMSO) showed the highest OFX adsorption capacity of 646.86 mg/g. The higher BET surface area (34.7 m2/g), higher total pore volume (0.4224 cm3/g), and larger pore size (48.63 nm) of the HOF–DMSO sample, along with its strong interactions with OFX molecules, such as hydrogen bonding, electrostatic interactions, π–π stacking interactions, and pore filling, contributed to this high adsorption capacity. This sample not only exhibited good structural stability against harsh conditions (acidic and basic solutions) but also showed excellent stability during the adsorption experiment and cyclic adsorption–desorption experiments. Therefore, it can be proposed that MA-based HOFs are promising adsorbent materials for water treatment applications and will have a bright future in this field.