Aqueous inks based on covalent organic frameworks for polyols electrochemical sensing

Covalent organic frameworks (COFs) are crystalline, porous, and chemically stable nanomaterials, whose tunable structure and extended π-conjugation make them promising candidates for electrochemical sensing. However, their integration into practical sensing devices is severely hindered by their intrinsic insolubility and poor processability, which impede conventional film deposition. Inkjet printing could address these processing drawbacks enabling the versatile and cost-effective production of COF-based sustainable sensor. While polyol quantification traditionally relies on enzymatic sensors, these systems are constrained by narrow substrate specificity and operational instability under non-physiological pH and temperature conditions. To overcome these limitations, herein an aqueous ink based on a copper-metalated porphyrin-based COF is presented for non-enzymatic polyol sensing. The Cu-functionalized framework directly catalyses the electro-oxidation of polyols under alkaline conditions, thus circumventing enzymatic restrictions to enable robust and versatile voltammetric detection. Polyols of environmental and biomedical relevance, such as ethylene glycol, glucose, and erythritol, are herein tested. After testing the electrochemical performance of the system, a proof-of-concept application of the sensor for ethylene glycol has been explored toward the enzymatic degradation of PET microplastics. A water-based ink formulation is engineered to match the strict requirements of inkjet printing, yielding a printable COF dispersion with the potentiality to be used in successive studies to obtain fully-inkjet-printed paper-based sensors.