A water-stable Zn4O-based MOF decorated with carbazolyl chromophores for multi-responsive fluorescence sensing of Fe3+, Cr2O72− and nitro-compounds

Abstract

A novel luminescent isoreticular metal–organic framework Zn₄O(ECMTDC)₃·10DMF (Cz-MOF-1), where ECMTDC denotes 3-(9-ethyl-9H-carbazol-3-yl)-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylate and DMF denotes N,N-dimethylformamide, was successfully synthesized via solvothermal methods from Zn(NO₃)₂·6H₂O and H₂ECMTDC in DMF. Powder X-ray diffraction experiments along with scanning electron microscopy images indicate that Cz-MOF-1 has excellent water stability compared with other Zn₄O-based MOFs, which can be attributed to the hydrophobic surroundings around the Zn₄O clusters formed from N-ethylcarbazolyl and methyl groups. Cz-MOF-1 displays a strong deep blue light emission (452 nm) and a quantum efficiency of 3.74%, and has high selectivity and sensitivity for the detection of Fe³⁺, Cr₂O₇²⁻ and DCN. Furthermore, the possible luminescence sensing mechanisms have been discussed in detail, which are supported by PXRD analysis, UV-vis spectroscopy and density functional theory (DFT).