Metal-organic framework films functionalized with nonionic conjugated polythiophenes for visual detection of PAHs

Natural and anthropogenic activities lead to the generation of polycyclic aromatic hydrocarbons (PAHs), persistent contaminants that adversely affect the environment and public health. However, highly sensitive, fast, and portable techniques for the detection of PAHs remain a technological challenge. The rapid analysis of urinary levels of 1-hydroxypyrene (1-HP) would enable PAH carcinogens to be measured using biomonitoring techniques. Here, we demonstrate biocompatible, easy-to-use, and portable sensors based on novel π-conjugated metal-organic frameworks (MOFs) for the detection of 1-HP. These sensors were developed by incorporating nonionic conjugated polythiophenes with a PLQY as high as 65% into lanthanide-MOFs (CP1-Eu-MOF and CP2-Eu-MOF) using an in-situ synthesis strategy. The emission of the sensors can be effectively quenched by 1-HP via hydrophobic, π–π stacking, and hydrogen bonding interactions. Significantly, the unique structure of CP2-Eu-MOF sensor displays superior performance with enhanced sensitivity (LOD ~1.02 pM) that is 1.63 times higher than that of CP1-Eu-MOF (LOD ~1.66 pM). More importantly, we successfully demonstrated the possibility of employing wax-printed paper in combination with a fast and cost-effective smartphone for rapid 1-HP detection. Moreover, portable sensory films were fabricated by incorporating CP2-Eu-MOF into a poly(vinylidene difluoride) (PVDF) matrix to produce CP2-Eu-MOF/PVDF films for the visual detection of 1-HP levels as low as 25 pM. Finally, the feasibility of successfully analyzing the levels of 1-HP in urine was verified by testing real urine samples with satisfactory recoveries of 94.1-103.5%. This method provides new pathways for the biomonitoring of polyaromatic environmental pollutants.