Efficient and Rapid Synthesis of a Solvent and Ion-Responsive Luminescent Copper 2-Aminoterephthalate Thin Film

Metal–organic coordination polymers are promising optical sensing materials due to their tunable physical and chemical properties, which can be controlled through careful selection of metal centers, organic linkers, and/or reaction conditions. The fabrication of coordination polymers in thin film form is particularly desirable for sensor development because it facilitates integration with sensing platforms such as optical fibers, enables sensing material recovery and regeneration, and can enhance analyte uptake during analysis. However, many thin film fabrication techniques are tedious and require high temperatures and/or expensive equipment, creating a significant barrier toward scalable production. Here, coordination polymer thin films comprised of copper and 2-aminoterepthalic acid are selectively grown within 30 min at room temperature and under ambient atmosphere using an aluminum-doped zinc oxide template, circumventing the long time and high equipment costs typically associated with thin film production. The films luminesce in the presence of polar protic solvents and exhibit enhanced emission in the presence of aluminum(III) ions, an economically critical metal according to the 2022 United States Geological Survey. The “turn on” luminescent response to aluminum is selective against 15 other metal ions commonly found in environmental streams, and is highly sensitive, with estimated detection limits down to 120 parts-per-billion in water. As a proof-of-concept, the films were evaluated on diluted fly ash streams, with luminescent signals that qualitatively correlate with inductively coupled plasma mass-spectrometry analysis. Taken together, this work presents a promising route toward the scalable production of optically active coordination polymer films.