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^II₆[(S,S)-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^II₆[(S,S)-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^II₆[(S,S)-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.