AIE-Active Fluorescent Porous Polymers for Recognizable Detection of Imidacloprid and Structure–Property Relationship

Aggregation-induced emission (AIE)-active aromatic tetraaldehydes are utilized as starting monomers to create two fluorescent polymers (PAN-TPEs) with hierarchical pores ranging from micropores (1.4–1.9 nm) to mesopores (3.8–26.2 nm). Their chemsensing properties for five pesticides, including imidacloprid, acetamiprid, triflumizole, lambda-cyhalothrin, and indoxacarb, are studied. It is found that the Stern–Volmer quenching coefficient and the limit of detection for imidacloprid in the water medium reach 53 745 M–1 and 28 ppb, respectively, which are much superior to those of the reported porous materials in the literature and exceed 3–10 times of the other four pesticides. Moreover, the polymers exhibit fast fluorescence response for imidacloprid (less than 4 s), and the detection sensitivity is nearly not affected by the common cations and anions. Additionally, the studies reveal that, for the polymer sample with narrower pore channels, the recognition ability for imidacloprid strongly depends on the molecular volumes of pesticides, whereas in the case of the polymer with larger pore sizes, the inner filter effect and the photoinduced electron transfer between the pesticides and the chromophore groups in the polymer skeleton become the major factors. The results are of significance for understanding the effects of porosity parameters and AIE groups in fluorescent porous polymers on the recognizable detection of imidacloprid from other pesticides.