Amidinium sulfonate hydrogen-bonded organic framework with fluorescence amplification function for sensitive aniline detection

Although the construction of specific functional crystalline materials is still challenging, the multi-component molecular assembly has become a key solution for the design of functional materials. Here, we report a hydrogen-bonded organic framework (HOF) material FJU-360 constructed from disodium 6‑hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate (SSY) and terephthalimidamide. The charge-assisted hydrogen bonding between amidinium and sulfonate makes FJU-360 produce much stronger fluorescence than SSY, and can be used as a luminescence sensor to rapidly quench aniline through luminescence quenching. FJU-360 is sensitive and highly selective for the detection of aniline, and the detection limit reached 3.2 nmol/L, which is the lowest value reported currently. The mechanism of aniline response was analyzed through the aniline@FJU-360 single crystal structure, and the luminescence mechanism was clarified through density function theory calculations. This work is an important step towards the rational synthesis and assembly of sensing materials. Disodium 6‑hydroxy-5-[(4- sulfophenyl ) azo ]-2-naphthalenesulfonate (SSY) and terephthalimidamide self-assembled hydrogen-bonded organic framework material FJU-360 exhibits ultra-high fluorescence response to aniline with a detection line as low as 3.2 nmol/L.