Enhanced TNT Vapor Detection via a Donor–Acceptor-Based Imine Cross-Conjugated Aggregation-Induced Enhanced Emission Active Porous Polymer

Abstract

The development of sensitive and selective probes for the detection of nitro explosives is critical for ensuring public safety and environmental monitoring. Among various detection strategies, porous materials offer significant advantages for vapor-phase detection due to their high surface area and analyte-trapping capability. In this study, we report the design and synthesis of an electron-rich system with a donor–acceptor (D–A)-based organic porous polymer (P1), incorporating triphenylamine as the electron-donating unit and imine-conjugated sulfone (SO₂) functionalities as electron acceptors. The resulting aggregation-induced enhanced emissive (AIEE) porous network exhibits selective fluorescence quenching in the presence of nitro explosives, particularly picric acid (PA) and 2,4,6-trinitrotoluene (TNT) in aqueous media. Notably, in the vapor phase, P1 demonstrates a strong and selective response to TNT vapors with a detection limit of 50 ppb, attributed to its higher vapor pressure compared to PA. Experimental and density functional theory (DFT) mechanistic investigations revealed distinct sensing pathways: Förster resonance energy transfer governs PA detection, while photoinduced electron transfer is responsible for TNT sensing. The high porosity of the polymer, confirmed through FESEM imaging and BET surface area analysis, facilitates efficient analyte capture, contributing to its superior vapor-phase sensitivity.