A functionalized UiO-66 MOF for turn-on fluorescence sensing of superoxide in water and efficient catalysis for Knoevenagel condensation

In the present work, a new MOF material of the UiO-family called Zr-UiO-66-NH-CH2-Py (1) has been obtained by the solvothermal technique and successfully characterized. The MOF structure was assembled with 2-((pyridin-4-ylmethyl) amino) terephthalic acid (H2BDC-NH-CH2-Py) as linker and Zr4+ ion. The activated form of 1 (called 1 ') exhibits considerable thermal and chemical stability. Compound 1 ' showed a very rapid and selective response for the fluorometric sensing of superoxide (O-2(-)) in aqueous medium even in the presence of the potentially competitive reactive oxygen species (ROS). The limit of detection value for O-2(-) sensing is 0.21 mu M, which is comparable with those of the reported O-2(-) sensors. This is the first MOF based fluorescent sensor for the detection of O-2(-). The response time of this MOF sensor for O-2(-) is very short (240 s). On the other hand, 1 ' was employed as a solid heterogeneous catalyst for Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate at 80 degrees C in ethanol resulting in a very high yield of the desired product. The effects of the esterified linker ((CH3)(2)BDC-NH-CH2-Py) and the corresponding metal salt (ZrCl4) on this catalytic reaction were examined separately. We have also tested the substrate scope elaborately for the catalytic reaction promoted by catalyst 1 '.