Diamino group-functionatized Zr-based metal-organic framework for fluorescence sensing of free chlorine in the aqueous phase and Knoevenagel condensation

We developed a porous diamino group-functionalized Zr(IV) metal- organic framework (MOF). The synthesized MOF has a similar structure to DUT-52 (DUT = Dresden University of Technology), which has a face-centered cubic structure with an Fm3m space group. The synthesized material (DUT-52-(NH2)(2)-1) was solvent exchanged with methanol (MeOH) and activated at 100 degrees C overnight. Both the as-synthesized and activated materials (DUT-52-(NH2)(2)-1') are thermally stable until 300 degrees C. The Brunauer-Emmett-Teller (BET) surface area of DUT-52-(NH2)(2)-1' was found to be 413 m(2) g(-1). DUT-52-(NH2)(2)-1' showed a significant quenching of fluorescence response after coming in contact with free chlorine (CIO-) in an aqueous medium. The selectivity of DUT-52-(NH2)(2)-1' towards ClO- was not significantly hampered in the presence of any competitive ion. The limit of detection (LOD) value was found to be 0.08 mu M in phosphate-buffered saline (PBS, pH = 7.4). DUT-52-(NH2)(2)-1' is recyclable and very sensitive towards ClO-. Moreover, the paper strip method was developed for onsite identification of ClO-. Furthermore, the catalytic activity of DUT-52-(NH2)(2)-1' was tested in the Knoevenagel condensation between benzaldehyde and cyanoacetamide. The experimental results clearly indicate that DUT-52-(NH2)(2)-1' exhibits high activity with very high selectivity towards condensation products. The solid was reusable three times with no decay in its activity, as evidenced by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and fourier transform infrared (FT-IR).