A Functionalized UiO-66 MOF for Turn-On Fluorescent Sensing of Superoxide in Water and Efficient Catalysis of Knoevenagel Condensation
In the present work, a new MOF material from UiO-family called Zr-UiO-66-NH-CH2-Py (1) has been obtained by solvothermal technique and successfully characterized. The MOF structure is contains 2-((pyridin-4-ylmethyl) amino) terephthalic acid (H2BDC-NH-CH2-Py) linker. The activated form of 1 (called 1′) exhibits considerable thermal as well as chemical stability. Compound 1′ showed very rapid and selective response for the fluorometric sensing of superoxide (O2•−) in aqueous medium even in presence of the potentially competitive reactive oxygen species (ROS). The limit of detection value for O2•− sensing is 0.21 μM, which is comparable with the reported O2•− sensors. This is the first MOF based fluorescent sensor for the detection of O2•−. The response time of this MOF sensor for O2•− is very short (60 s). On the other hand, 1′ was employed as a solid heterogeneous catalyst for Knoevenagel condensation between benzaldehyde and ethyl cyanoacetate at 80 °C in ethanol by providing a very high yield of the desired product. The effects of the free linker (H2BDC-NH-CH2-Py) and corresponding metal salt (ZrCl4) on this catalytic reaction were examined separately. We have also scrutinized the substrate scope elaborately for the catalytic reaction by catalyst 1′.