Efficient removal of drugs of abuse from drinking water using metal–organic frameworks

The presence of residues of drugs of abuse in potable water is a growing concern worldwide. Different studies have detected traces of opioids, cocaine, amphetamines, or cannabinoids in surface water, groundwater, and even treated drinking water, which is a clear indicator of insufficient removal during wastewater treatment processes. These substances may persist in the environment, posing potential long-term risks to human health and ecosystems, and consequently, making the quest for efficient decontamination technologies mandatory. Herein, we explore the use of a family of six eco-friendly water-stable isoreticular metal-organic frameworks (MOFs) and multivariate MOFs (MTV-MOFs), prepared from amino acids, as adsorbents for the removal of a mix of 29 drugs of abuse from water. Among them, the MOF prepared from the natural amino acid l-methionine, with the formula {Ca^IICu^II ₆[(<i>S</i>,<i>S</i>)-methox]₃(OH)₂(H₂O)}·16H₂O (3), features channels densely decorated with thioalkyl (-CH₂CH₂SCH₃) residues and exhibits an outstanding removal efficiency being capable to remove them almost completely in a single capture step under dynamic solid-phase extraction conditions (less than 30 seconds). Also, the removal performance of 3 toward the highly concerning drug fentanyl -responsible for a large number of deaths due to overdose in the United States and Canada was further investigated. 3 is capable of capturing fentanyl entirely, for at least 16 consecutive cycles, outperforming the current reference material, powdered activated carbon (PAC). Finally, the crystal structures of two host-guest adsorbates with amphetamine molecules embedded within the channels of two of the MOFs of the family {Sr^IICu^II ₆[(<i>S</i>,<i>S</i>)-mecysmox]₃(OH)₂(H₂O)}·15H₂O (2') and (3) could be resolved, helping to unveil the interactions between the drugs and the MOF matrix. Moreover, the crystal structure of another host-guest adsorbate with fentanyl molecules hosted in MOF Sr^IICu^II ₆[(<i>S</i>,<i>S</i>)-methox]₃(OH)₂(H₂O)}·16H₂O (3') was also elucidated. Overall, these properties situate MOF 3 among the most attractive adsorbents for the challenging removal of such emerging pollutants and it is a viable alternative for application in a real-world environment.