β-Diketone Boron Difluoride Integrated Olefin-Linked Luminescent Conjugated Porous Polymers as Nitroaromatic Sensors

The detection of nitroaromatic compounds (NACs) is critical due to their extensive use in explosives and their toxic environmental impact. Conjugated porous polymers (CPPs) having fluorescence properties are highly effective at detecting these NACs. Here, aiming to establish the structure-property relationship that governs nitroaromatic sensing, β-diketone boron difluoride (ABF₂)-based two luminescent CPPs (TPA-ABF₂ and TTz-ABF₂) have been synthesized through Knoevenagel condensation. The comprehensive spectroscopic and photophysical studies revealed that the super-amplified quenching by these polymers followed Perrin's quenching-sphere-of-action model. TPA-ABF₂ exhibited higher quenching efficiencies toward moderately electron-deficient (4-NA, 4-NPH) compounds, with static quenching constants (K_S) of 1.7 × 10⁴ M^-1, 1.5 × 10⁴ M^-1, and detection limits of 3.62, 3.10 µM, respectively. The TTz-ABF₂ preferentially responded to relatively highly electron-deficient analytes PA, 4-NPH, 2,-DNP, and 4-NA and showed significantly high static quenching constants in the range of 1 × 10⁴ to 5 × 10⁴ M^-1, along with detection limits of 3 to 6 µM. The high static quenching constants and lower detection limits position these ABF₂-based CPPs as effective luminescent probes for the detection of nitroaromatics.