Imidazolium-based ionic conjugated microporous polymer as a versatile SPE adsorbent for trace triazine herbicides in water and juice samples

Efficient monitoring of triazine herbicide residues is essential for safeguarding environmental and food safety. In this work, an innovative imidazolium-functionalized ionic conjugated microporous polymer (Im-CMP) was developed through Sonogashira–Hagihara coupling polymerization, and for the first time utilized as an adsorbent for solid-phase extraction (SPE) to enrich seven triazine herbicides from environmental water and fruit juice samples. Comprehensive characterizations confirmed that Im-CMP possessed a stable porous structure, high thermal stability, abundant π-π conjugated framework, and excellent hydrophilicity (water contact angle: 25.1°) derived from imidazolium ionic moieties, which solved the defect of poor aqueous dispersibility of traditional neutral CMPs. Density functional theory calculations and independent gradient model analysis revealed that the high extraction capacity of Im-CMP for triazine herbicides was dominated by efficient π–π stacking interactions, with synergistic contributions from directional weak interactions including C–H···π and N–H···π. Under optimized conditions, the established Im-CMP-SPE-HPLC-MS/MS method exhibited a wide linear range (0.25–250 ng·L⁻¹), low detection limits (0.03–0.11 ng·L⁻¹), high enrichment factors (387–554), and satisfactory recoveries (77.4–110.7%) with good precision. Additionally, the Im-CMP adsorbent demonstrated excellent reusability for nine cycles and consistent batch-to-batch reproducibility. This work not only provides a rational design strategy for ionic-functionalized porous adsorbents for sample pretreatment, but also establishes a sensitive, reliable and practical analytical method for the trace monitoring of triazine herbicides in complex environmental and food matrices, and further expands the application of ionic conjugated microporous polymers in the field of pesticide residue analysis.