A new Keggin-type polyoxometallate-based bifunctional catalyst for trace detection and pH-universal photodegradation of phenol

The widespread application of phenolic substances in the field of food, medicine and industry, is harmful to the environment and human health. Therefore, it is very important to develop a convenient and effective method to detect and degrade phenolic compounds. Herein, we report a new keggin-type polyoxometallate-based metal-organic complex self-assembled under solvothermal condition, {[Cu(dap)(3-PA)](4)(SiW12O40)(H2O)(2)}<middle dot>2H(2)O (1, dap = 1,2-diaminopropane, 3-HPA = 3-pyridineacrylic acid). 1 shows an interesting 1D ladder-like structure. As a bifunctional catalyst, 1 can be employed as a colorimetric sensor toward phenol with the relatively low detection limit (LOD) of 0.36 mu mol/L (S/N = 3) in the wide range (0.001-0.1 mmol/L). The title colorimetric sensor is applied to determine phenol in various water environment with good recoveries ranging from 95%-105%. In addition, 1 also exhibits excellent photocatalytic degradation toward phenol under visible light with the highest removal efficiency at 96% for 100 min and wide pH universality. The selectivity, stability and reliability of the detection of 1 towards phenol, as well as the detection for 4-chlorophenol, o-cresol, 4-nitrophenol and phloroglucinol were studied. Furthermore, the photocatalytic reaction kinetics and the mechanisms of photodegradation of phenol were also investigated in detail.