Density functional theory study on catalytic performance of Si-doped and Mg-doped monoclinic ZrO2 for the direct synthesis of dimethyl carbonate from CO2 and methanol

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol over the single-atom Si-doped and Mg-doped hydroxylated monoclinic (m) ZrO2(1¯11) surface (named as SHM and MHM surfaces) was explored by density functional theory (DFT) calculations, which indicated that DMC formation originated from *CH3O reacting with *CH3OCO on both surfaces. Compared with the hydroxylated m-ZrO2(1¯11), the doping of Si atom significantly increased the catalytic activity, but the doping of Mg atom distinctly did the opposite. The excellent catalytic performance and adjusted reaction pathway on SHM surface were strongly attributed to the influence of decreased band gap greater than that of the enhanced Brønsted acidity. However, the hydroxyl group and hydrogen atom from the dissociation of H2O molecule on MHM surface were reduced to H2O molecule by the doping of single-atom Mg, which leaded to the inexistence of Brønsted acid site and the larger band gap for the decreased catalytic activity. The results provide a theoretical basis for the influences of the dopants on the catalytic performance of m-ZrO2, and help the design of high performance ZrO2 catalysts for the direct synthesis of DMC.