Selective and Sensitive Recognition of Specific Types of Toxic Organic Pollutants with a Chemically Stable Highly Luminescent Porous Organic Polymer (POP)

Abstract

The excessive use of anthropogenic wastes, such as emerging antibiotics and pesticides, has led to serious water pollution. Therefore, selective identification of those specific types of pollutants in wastewater is of significance owing to their direct detrimental impact upon human health. For practical requirements, a potential sensory material is highly desirable for detection of antibiotics and pesticides in water. As an advanced class of porous materials, porous organic polymers (POPs) are considered a potential candidate for the detection of micropollutants. Herein, we investigated the selective fluorescence quenching mechanism of a highly luminescent, electronically rich chemically stable POP (IPPOP-1) toward detection of antibiotics and pesticides in an aqueous medium. IPPOP-1 exhibited a selective strong quenching response in the presence of electron-deficient antibiotics (such as nitrofurantoin [NFT] and nitrofurazone [NFZ]) and pesticides like chloropyriphos (CHPS) and nitrofen, among others. IPPOP-1 was found to be highly sensitive to NFT and NFZ at trace levels, and the detection limits were found as 0.046 and 0.045 mM, respectively. On the other hand, in the case of the pesticides, CHPS and nitrofen, the detection limits were 0.470 and 0.471 mM, respectively. After the detection test, IPPOP-1 could be regenerated for further use without any apparent loss of function. Moreover, detailed mechanism of the detection ability of IPPOP-1 were elucidated with the help of a time-resolved photoluminescence lifetime decay study and the density functional theory (DFT). All of these studies suggested that both the fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) processes are responsible behind such selective emission quenching. Furthermore, isothermal titration calorimetry (ITC) experiment was carried out in addition to demonstrate IPPOP-1 being able to detect electron-deficient antibiotics in trace amounts in simulated hospital wastewater. Finally, IPPOP-1-based mixed-matrix membranes (MMMs) were fabricated and employed to mimic real-time antibiotic detection in water.