Stable hydrogen-bonded organic frameworks for selective fluorescence detection of Al and Fe ions

• Published in: CrystEngComm 2021-12, Vol.23 (47), p.8334-8342
• Main Authors: Xiao, Cheng-Quan, Yi, Wen-Hai, Hu, Jun-Jie, Liu, Sui-Jun, Wen, He-Rui
• Format: Article
• ISSN: 1466-8033
• DOI: 10.1039/d1ce01182k

Four new hydrogen-bonded organic frameworks (HOFs) with the formulas {[H 4 TCPE·bpa]·(CH 3 OH·H 2 O)} n ( 1 ), {[H 4 TCPE·bpe]·(CH 3 OH·0.56H 2 O)} n ( 2 ), {[H 4 TCPE·bpa]·CH 3 OH} n ( 3 ) and {[H 4 TCPE·bpe]·(0.41CH 3 OH·0.59CH 3 CN)} n ( 4 ) (H 4 TCPE = tetrakis(4-carboxyphenyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene) have been prepared under different conditions and structurally characterized. X-ray crystallographic analysis reveals that the hydrogen bond strengths of 3 and 4 synthesized by solvothermal method are much stronger than those of 1 and 2 prepared by the volatilization method. An obvious fluorescence shift was observed during the sensing process of 3 and 4 toward Al 3+ and Fe 3+ ions. For HOF 3 , a red-shift emission ( ca. 28 nm) occurs upon the addition of Al 3+ ion. When Al 3+ ion is added to HOF 4 in acetonitrile suspension, a red-shift emission ( ca. 30 nm) as well as a great fluorescence enhancement happens. Both 3 and 4 exhibit strong fluorescence quenching with high selectivity and sensitivity toward Fe 3+ ion. In addition, they display relatively good stabilities as well as reusability. Therefore, HOFs 3 and 4 are excellent fluorescent sensors toward Al 3+ and Fe 3+ ions. Two pairs of HOFs were prepared with H 4 TCPE ligand under different conditions, and 3 and 4 have high stability and exhibit fluorescence quenching and enhancement toward Fe 3+ and Al 3+ ions, respectively.