A novel ketone-functionalized carbazolic porous framework named PBPMCz is presented for fluorometric determination of p-nitroaniline (PNA). PBPMCz was prepared by FeCl3-promoted oxidative coupling polymerization of 1,3,5-tris((4-(9H-carbazol-9-yl)phenyl)methanone-1-yl)benzene. The polymer possesses a BET surface area of above 907 m2∙g-1 with a pore volume of 0.72 cm3∙g-1. Compared to the ketone-free framework, the green fluorescence of the probe PBPMCz is more strongly quenched by PNA. Figures of merit include (a) excitation/emission wavelengths of 366/540 nm; (b) a Stern-Volmer constant (Ksv) of 2.2 × 104 M-1, and (c) a detection limit of 1.1 μM. Furthermore, PBPMCz shows different quenching behaviors of PNA compared with o-nitroaniline and m-nitroaniline. The excellent performance of the fluorescent probe is ascribed to the abundant carbazole sites and ketone groups in PBPMCz. These facilitate the electron transfer and hydrogen-bonding interactions between PNA and the polymer. Graphical abstract Schematic presentation of a luminescent carbazolic porous organic framework (CzPOF) modified with keto groups. It shows ultra-sensitivity to quenching by PNA over other nitroaniline isomers.
Keywords: Carbazolic porous framework; Detection limit; Electron transfer; Fluorescence sensing; Nitroaniline isomers; Oxidative coupling; Quenching mechanism.