Hydrothermal synthesis, structure, and catalytic properties of a (4,6)-connected framework constructed from Keggin-type polyoxometalate units and tetranuclear copper complexes
Jiayu Sun, Zi-Lan Wang, Zhong Zhang, Guo‐Cheng Liu, Xiuli Wang
Abstract
Under hydrothermal condition, a new Keggin-type polyoxometalate(POM)-based metal-organic complex, namely H<sub>4</sub>{[Cu<sub>4</sub>(EDDP)<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>]<sub>1.5</sub>(SiW<sub>12</sub>O<sub>40</sub>)}∙7.5H<sub>2</sub>O (<strong>CuW-EDDP</strong>, H<sub>4</sub>EDDP = ethylenediamine-N,N'-dipropionic acid) was synthesized by reaction of Na<sub>10</sub>[A-<em>α</em>-SiW<sub>9</sub>O<sub>34</sub>]·18H<sub>2</sub>O and CuCl<sub>2</sub>·2H<sub>2</sub>O in the presence of H<sub>4</sub>EDDP ligand and characterized by X-ray diffraction (powder, single-crystal), Infrared radiation (IR) spectra, elemental analysis, and thermogravimetry. Interestingly, <strong>CuW-EDDP</strong> features a three-dimensional structure with (4,6)-connected built up from [SiW<sub>12</sub>O<sub>40</sub>]<sup>4-</sup> units and tetranuclear-copper complexes [Cu<sub>4</sub>(EDDP)<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>].<strong> CuW-EDDP</strong> as an effective heterogeneous catalyst exhibited excellent performance, good reusability and structural stability in the selective oxidation of methyl phenyl sulfide (MPS) with high conversion (100%) and selectivity (98%) within 30 min. Furthermore, the catalytic activity of <strong>CuW-EDDP</strong> toward the oxidation of other sulfide derivatives was also investigated.