A luminescent metal-organic framework with pre-designed functionalized ligands as an efficient fluorescence sensing for Fe3+ ions

Metal-organic frameworks are a class of attractive materials for fluorescent sensing. Here, we report the exploration of fluorescent Zn-based amine/azine-functionalized MOF, TMU-17-NH2, ([Zn(NH2-BDC)(4-bpdb)].2DMF; NH2-BDC = amino-1,4-benzenedicarboxylic acid, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-2,3-butadiene) for highly selective and sensitive detection of Fe3+ in DMF solution. TMU-17-NH2 shows fast recognition of Fe(3+)ion with a response time of < 1 min and detection limit of 0.7 mu M (40 ppb), and the luminescence is completely quenched in 10(-3) M DMF solution of Fe3+. Furthermore, the static quenching constant is calculated to be upper than 41,000 M-1 by the fluorescence titration experiment in low concentration of Fe3+. No interferences from 250 mu M As3+, Cd2+, Zn2+, Co2+,Ni2+, Cu2+, Pb2+, Mn2+ and Al3+ were found for the detection of Fe3+. The efficient fluorescent quenching effect is attributed to the photoinduced electron transfer between Fe3+ ions and the amino-functionalized ligand in this MOF. Moreover, the introduced azine N donors in the 4-bpdb ligand of TMU-17-NH2 additionally donate their lone-pair electrons to the Fe3+ ions, leading to significantly enhanced detection ability. Furthermore, the regenerated TMU-17-NH2 still has high selectivity for Fe3+ ions, which suggests that the functionalized TMU-17-NH2 is a promising luminescent probe for selectively sensing of Fe(3+)ions.