A luminescent cationic MOF and its polymer composite membrane elicit selective sensing of antibiotics and pesticides in water

Abstract

Medicines and pesticides are being used excessively, misused, or abused in recent times, resulting in major environmental contamination and, more specifically, water pollution. Remediation of these anthropogenic wastes in ambient water holds the key to mitigating their bioaccumulation and the subsequent negative health impacts. To address this, here, we present a novel stable cationic metal–organic framework (MOF), [Cd(L)2(ClO4)2·xG]n (L = 1,1′-(5′-(4-(1H-imidazol-1-yl) phenyl)-[1,1′:3′,1′′-terphenyl]-4,4′′-diyl) bis(1H-imidazole); G = guest molecules), abbreviated as iMOF-14C (iMOF = ionic MOF; C = cationic). Composed of Cd(II), perchlorate and an imidazole ligand L, iMOF-14C exhibits selective photoluminescence (PL) quenching towards detecting a specific spectrum of antibiotics and pesticides from the contaminated water. It is also responsive to some nitro-functionalised toxins, viz. nitrofuran antibiotics, such as nitrofurazone (NFZ) and nitrofurantoin (NFT), as well as pesticides, including nitrofen (an herbicide) and chloropyriphos (CHPS). iMOF-14C presents high selectivity towards these target analytes even in the presence of other interfering antibiotics and pesticides, and it reveals a turn-off PL response towards trace levels of NFT and NFZ, with detection limits as low as 100 ppb and 20 ppb, respectively. Furthermore, it detects CHPS and nitrofen at 50 ppb and 250 ppb, respectively, i.e., among all porous solids, iMOF-14C stands out with record-high pesticide sensing performance. Upon hybridising iMOF-14C with low-cost polymer polyvinylidene fluoride (PVDF), the composite membrane iMOF-14C@PVDF overcomes processability issues oft-encountered with MOF powders while also exhibiting efficient sensing of antibiotics in water.