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

摘要

Herein, two indium-based metal organic frameworks (In-MOFs), namely [(CH3)(2)NH2][In(bpdc)(2)](DMF)(2) (1) and [(CH3)(2)NH2](3)[(In3Cl2)(bpdc)(5)](H2O)(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 InO8 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 CS2, a trace amount of Fe3+ 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 [(CH3)(2)NH2](+) cations in 2 can be replaced by an Eu3+ ion to generate 2@Eu3+ which exhibits a new characteristic sharp red emission of Eu3+. 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.