Synthesis and sulfide oxidation catalytic activity of a copper monosubstituted Keggin-type polyoxometalate-based supramolecular compound

Abstract

For the selective oxidation of sulfides, we synthesized a copper monosubstituted Keggin-type polyoxometalate-based supramolecular compound under hydrothermal conditions: {[(phen)₂Cu(H₂O)]₂[Cu(phen)₂]₂[H₂PW₁₁Cu(H₂O)O₃₉]₃}{[(phen)₂Cu]₂[H₂PW₁₁Cu(H₂O)O₃₉]}·4H₂O (1) (phen = 1, 10-phenanthroline). Single-crystal X-ray diffraction analysis shows that three coordination environments of Cu²⁺ are present in compound 1, with Cu1 being tetra-coordinated and Cu2 and Cu3 being penta-coordinated. The compound forms a 3D structure through hydrogen bonding and π–π interactions between various building blocks. Experimental results indicate that 1 exhibits excellent catalytic oxidizing activity for both thioethers and thiols. When using H₂O₂ as the oxidizing agent, all methyl phenyl sulfide (MPS) is converted within 2 h, and the selectivity of the product sulfoxide reaches 96%. When O₂ is employed as the oxidant, 1 is able to oxidize the 2-hydroxy-1-ethanethiol to the corresponding disulfide within 6 h. The good reusability of compound 1 in sulfide oxidation reactions has been verified through cycling experiments.