Polymerization Time-Optimized Covalent Organic Framework for Ultrasensitive Ethylene Glycol Sensing

Ethylene glycol (C₂H₆O₂) is a widely used yet toxic compound, requiring energy-efficient detection methods beyond prevalent high-temperature sensors. Here, an imine covalent organic framework (COF-TPC) was synthesized at room temperature (RT) using 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (Tp) and 2,5-dichlorobenzene-1,4-diamine (Pa-Cl) as ligands, with acetic acid as a catalyst. The structure-property relationship was investigated by controlling Schiff base reaction time (1-70 h), yielding four sensors (COF-T-30, COF-T-40, COF-T-50, and COF-T-60) for testing. Gas sensing data revealed that the COF-T-50 sensor exhibited a response of 6107% to 500 ppm C₂H₆O₂, significantly outperforming the other sensors. It also exhibited outstanding selectivity toward C₂H₆O₂ among 13 gases, along with excellent repeatability and moisture resistance. DFT calculations elucidated the adsorption mechanism and the origin of its exceptional selectivity. This work provides a new approach for rapid, stable C₂H₆O₂ detection using COFs, expanding their application scope.