Post‐Synthetic Functionalization of Covalent Organic Frameworks for Highly Sensitive and Selective Detection of Plasticizers

Here in, The nanoporous COF was synthesized by using 2-hydroxy-1,3,5-benzenetricarbaldehyde (BTC) and 2,5-diamino-1,4-benzenedithiol (2,5-DABT) under solvothermal conditions. The resulting COF features hydroxy groups from BTC selectively modified with longer octyl chains to impart hydrophobicity, while pendant thiol groups from 2,5-DABT anchor plasmonic silver (Ag) nanoparticles, yielding a superhydrophobic nanoporous material (denoted as Octyl-COF-SH@Ag). Indeed, the resultant Octyl-COF-SH@Ag hybrid serves as an efficient surface-enhanced Raman scattering (SERS) platform for the detection of various phthalic acid esters, including dimethyl phthalate (DMP), diphenyl phthalate (DPhP), dibutyl phthalate (DBP), diheptyl phthalate (DHeptP), dioctyl phthalate (DOP), dinonyl phthalate (DNP), and diisodecyl phthalate (DIDP), demonstrating exceptional sensitivity with the lowest detectable nanomolar concentration for DMP. Moreover, the resultant hybrid exhibited excellent stability and enabled rapid, highly sensitive, and selective detection of phthalic acid esters through the synergy between AgNPs and Octyl-COF-SH, which enhanced hot spot formation, analyte adsorption, and π-π interactions, making SERS combined with chemometric techniques a powerful approach for plasticizer detection. Furthermore, density functional theory (DFT) calculations were performed to elucidate the interaction between Octyl-COF-SH@Ag and phthalic acid esters, highlighting its selective detection of DMP over DBP.