Efficient Synthesis of Diphenyl Carbonate from CO2, Phenol, and Carbon Tetrachloride under Mild Conditions

Diphenyl carbonate (DPC) has outstanding practical potential, especially as a key building block for the phosgene-free synthesis of polycarbonate (PC) in the chemical industry. The synthesis of DPC from CO2 has been investigated for decades, but exploring highly efficient catalytic systems is still challenging. Herein, an efficient catalytic system for the direct synthesis of DPC from CO2, phenol, and carbon tetrachloride was developed by using a ZnCl2/copper triflate (Cu(OTf)2) composite catalyst. For the first time, high yield and high selectivity were achieved for DPC synthesis under mild conditions, even at atmospheric pressure. Carefully designed control experiments and DFT studies indicated that the synergistic activation of Cu(OTf)2 and its anion complex with ZnCl2 for phenol and CO2 led to a remarkably improved catalytic activity through a Lewis acid-assisted catalysis. This study not only provides a new strategy for efficient preparation of DPC but also offers an effective pathway for better CO2 utilization.