Single-step catalytic synthesis of diphenyl carbonate over transition-metal-substituted Keggin-type tungstophosphoric acid

Single-step catalytic synthesis of diphenyl carbonate (DPC) through the transesterification of dimethyl carbonate (DMC) and phenol could be firstly arrived by using the transition-metal-substituted polyoxometalates (TMS-POMs) K₅[PW₁₁O₃₉M(H₂O)]/TiO₂ system (M = Mn^II, Co^II, Ni^II, Cu^II, Zn^II). The catalytic activity of this transesterification was strongly influenced by the type of transition metal in the TMS-POMs. Among them, the K₅[PW₁₁O₃₉Zn(H₂O)]/TiO₂ catalytic system showed the highest activity and selectivity for DPC. The conversion of phenol reached 12.8%, and the selectivity to DPC was 83.6%. The turnover number (TON) reached 6.44 × 10⁴ mol/mol [PW₁₁O₃₉Zn(H₂O)]^5-/TiO₂. A possible mechanism that the transition metal in the polyoxometalates anchored DMC to form intermediate compound in the transesterification was proposed.