Naphthalene-anchored ETTA-based 2D-covalent organic frameworks exhibiting restricted intramolecular rotation for fluorescence sensing of nitroaromatic compounds

초록

The development of cost-effective and efficient sensors for nitroaromatic compounds (NACs) is crucial due to their toxic and explosive nature. Herein, we report the green synthesis of a naphthalene-anchored ETTA (ethanetetrayl-tetra-aniline)-based 2D covalent organic framework (ETTA-2DCOF) via a Schiff-base reaction, avoiding toxic reagents and harsh conditions. Structural analysis revealed a well-defined crystalline framework with dual porosity, excellent stability, broad fluorescence emission (402-424 nm), and a long lifetime (7.19 ns). As a fluorescent sensor, ETTA-2DCOF exhibits exceptional performance for TNP detection, including a wide detection range (0.5-25 ppm), high sensitivity (Ksv = 5.86 x107 M-1; Kq = 0.815 x1016 M-1.s-1), high quenching efficiency (96.42 +/- 1.37 %), ultralow detection limit (0.41 ppb), excellent selectivity, and superior reusability. Importantly, the sensor achieved 90.91 +/- 0.79 % and 86.93 +/- 1.80 % TNP recovery from ground and river water, respectively. The outstanding performance is attributed to the unique combination of it-electron-rich units with enhanced restricted intramolecular rotation, dual-porous crystalline structure, and involvement of rapid dynamic-quenching mechanism. This study demonstrates the critical role of RIR units in both structural integrity and sensing functionality and establishes a new approach for designing high-performance 2DCOF-based fluorescent sensors for environmental monitoring of hazardous pollutants.

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