Metal-organic frameworks (MOFs) have emerged as highly effective materials for the capture of pharmaceuticals and endocrine-disrupting compounds (EDCs) from aqueous environments. Among the most studied MOFs for this purpose are UiO-66 and MIL-101, which exhibit high surface areas, tunable porosity, and chemical stability. Their structural versatility allows for precise functionalization of organic linkers, enabling selective adsorption of target contaminants. The performance of these MOFs depends on several factors, including pore size, functional group interactions, and competitive adsorption effects in complex matrices. Additionally, regeneration methods such as solvent washing or thermal treatment play a crucial role in maintaining long-term efficiency. A life-cycle assessment of MOF synthesis further highlights the environmental implications of their production and use.
UiO-66, composed of zirconium clusters and terephthalate linkers, demonstrates exceptional stability in water and acidic conditions, making it suitable for wastewater treatment applications. Functionalization of its linkers with groups such as amino, nitro, or sulfonate enhances its affinity for specific contaminants. For example, UiO-66-NH2 exhibits improved adsorption of ibuprofen and diclofenac due to hydrogen bonding and electrostatic interactions. Similarly, MIL-101, constructed from chromium clusters and terephthalic acid, possesses large mesoporous cavities that facilitate the uptake of bulky pharmaceutical molecules. Modifications with hydrophobic or charged groups further optimize its selectivity for EDCs like bisphenol A and 17α-ethinylestradiol.
Competitive adsorption in complex aqueous matrices presents a significant challenge for MOF-based capture systems. Natural organic matter, inorganic ions, and other dissolved species can interfere with the removal efficiency of target pollutants. Studies indicate that UiO-66 retains high selectivity for carbamazepine even in the presence of humic acid, whereas MIL-101 shows reduced performance due to pore blockage. The presence of divalent cations like Ca²⁺ and Mg²⁺ can also influence adsorption by forming bridges between MOF surfaces and anionic contaminants. Understanding these interactions is critical for designing MOFs that maintain functionality in real-world wastewater conditions.
Regeneration of MOFs is essential for sustainable application. Solvent washing with ethanol or methanol effectively desorbs pharmaceuticals from UiO-66, with recovery rates exceeding 90% after multiple cycles. Thermal treatment at 150–200°C can also restore adsorption capacity by removing strongly bound contaminants, though excessive temperatures may degrade the framework. MIL-101 exhibits similar regeneration potential, though its chromium-based structure requires careful control to prevent metal leaching. The choice of regeneration method depends on the contaminant’s binding strength and the MOF’s thermal stability.
The life-cycle assessment of MOF synthesis reveals environmental trade-offs. The production of UiO-66 involves energy-intensive zirconium processing and organic solvent use, contributing to high carbon emissions. MIL-101 synthesis, while less energy-demanding, raises concerns over chromium toxicity and waste generation. However, the high adsorption capacity and reusability of MOFs can offset these impacts over their operational lifetime. Alternative synthesis routes, such as mechanochemical methods or water-based systems, are being explored to reduce environmental burdens.
In conclusion, UiO-66 and MIL-101 represent promising solutions for pharmaceutical and EDC removal, with functionalization strategies enhancing their selectivity and performance. Competitive adsorption effects necessitate careful material design, while efficient regeneration extends their usability. Despite the environmental costs of synthesis, their long-term benefits in water purification justify further development and optimization. Advances in greener production methods will be crucial for sustainable deployment in large-scale applications.