Engineering the heterogeneous photocatalytic activity of crystalline decatungstate-based coordination polymers

Abstract

Decatungstate (W₁₀O₃₂⁴⁻, DT) is a metastable polyoxometalate anion which presents excellent photocatalytic ability. In order to stabilize the DT species, four decatungstate-based coordination polymer compounds with different DT coordination modes, namely [Cu₂(3-bpo)₂(H₂O)₂(DMSO)₂][W₁₀O₃₂]·14H₂O (1), [Cu₂(3-bpo)₂(DMSO)₄][W₁₀O₃₂] (2), [Cu₂(4,4′-bipy)₄][H₂W₁₀O₃₂] (3) and [Cu(4,4′-bipy)₃(DMSO)(H₂O)][TBA][HW₁₀O₃₂]·H₂O (4) (DMSO = dimethyl sulfoxide, 3-bpo = 2,5-bis(3-pyridyl)-1,3,4-oxadiazole, 4,4′-bipy = 4,4′-bipyridine, TBA = tetrabutylammonium) were synthesized under controlled solvothermal conditions in the mixed solvent of DMSO and H₂O. The heterogeneous photocatalytic activity of these four compounds in the degradation of rhodamine B was tested and the results show that they possess fairly high photocatalytic activity without leaching of DT during the reaction. The effect of the coordination modes of terminal oxygen (O_t) atoms in DT anions on the activity was investigated.