Fluorescent In based MOFs showing “turn on” luminescence towards thiols and acting as a ratiometric fluorescence thermometer

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2019, Vol.7 (10), p.3049-3055
• Main Authors: Wu, Zhao-Feng, Tan, Bin, Velasco, Ever, Wang, Hao, Shen, Nan-Nan, Gao, Yu-Jie, Zhang, Xu, Zhu, Kun, Zhang, Guo-Yu, Liu, Yan-Yao, Hei, Xiu-Ze, Huang, Xiao-Ying, Li, Jing
• Format: Article
• Language: English
• Subjects: Cations; Chemical synthesis; Crystallography; Dyes; Europium; Fluorescence; Light emission; Metal-organic frameworks; Thiols; Ultraviolet radiation; White light
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C9TC00463G

Herein, two indium-based metal organic frameworks (In-MOFs), namely [(CH 3 ) 2 NH 2 ][In(bpdc) 2 ]·(DMF) 2 ( 1 ) and [(CH 3 ) 2 NH 2 ] 3 [(In 3 Cl 2 )(bpdc) 5 ]·(H 2 O) 5 (DMF) 2.5 ( 2 , bpdcH 2 = 4,4′-biphenyldicarboxylic acid), have been synthesized and characterized. By introducing a Cl − ion as a terminal ligand to break the symmetrical coordination environment of a typical InO 8 dodecahedron as that in a three dimensional (3D) compound 1 with a 4-connected and four-fold interpenetrating dia net topology, a chiral 2D compound 2 with unique double-helical chains along the c axis is generated. Fluorescence (FL) measurements indicate that both compounds demonstrate excellent FL sensing behaviour towards CS 2 , a trace amount of Fe 3+ ions and nitro-containing explosives. Notably, the layered 2 exhibits a unique “turn on” FL sensing behaviour towards thiol molecules, e.g. , cysteine and 1-butylmercaptan, by exfoliating 2 into a few-layer FL material. The detection mechanism was investigated in detail by multiple characterizations including but not limited to EDS, SEM and AFM. The [(CH 3 ) 2 NH 2 ] + cations in 2 can be replaced by an Eu 3+ ion to generate 2@Eu3+ which exhibits a new characteristic sharp red emission of Eu 3+ . More importantly, 2@Eu3+ can serve as a convenient ratiometric FL sensor for temperature, demonstrating obvious color changes from weak purple to red under UV light as the temperature increases. Furthermore, cationic green- and red-light emitting dyes incorporated with 2@dyes emit white light with 17.28% quantum yield.