Polarization-induced efficient charge separation in an electromagnetic coupling MOF for enhancing CO2 photocatalytic reduction

Rapid recombination of photogenerated carriers severely impairs the performance of photocatalysts, while polarization is an effective driving force for increasing the charge separation and hence improving the photocatalytic activity. In this work, a series of magnetoelectric-coupled layered metal-organic framework (MOF) catalysts with different Co-doped contents (denoted as Ni-MOF and CoxNi1-x-MOF) are fabricated with different polarities and employed as novel photocatalysts for CO2 photocatalytic reduction reaction. Our experiments show that the highest charge separation efficiency occurs in the Co0.1Ni0.9-MOF sample which has a maximal polarization. This Co0.1Ni0.9-MOF material has a best CO2 reduction performance of 38.74 μmol g-1h-1 which is at a high level in the currently reported layered materials. Meanwhile, it is found that a series of CoxNi1-x-MOF samples all display selectivity close to 100% for CO2 reduction to CO, which is desirable for industrial applications. Theoretical analysis shows that Co doping alters the degree of distortion of the asymmetrical Ni-centered octahedron {NiN2O4} in Ni-MOF by replacing Ni due to the magnetoelectric coupling effect and Jahn-Teller effect, which results in adjustable polarity of CoxNi1-x-MOF. This work provides new insights on how to improve photogenerated charge separation in MOF by enhancing polarization.