Novel bimetallic MIL-53(Fe/Mn) as dual cocatalysts promote charge separation efficiency of CdS for photocatalytic reduction of CO₂

Dual-co-catalyst-modified photocatalysts enhance charge separation efficiency, but the traditional dual co-catalyst is still difficult to get a high separation efficiency due to size and aggregation. Herein, we report bimetallic MIL-53(Fe/Mn) as dual co-catalysts with separate electron and hole mediators. CdS NPs were in-situ grown into MIL-53(Fe/Mn) at varying ratios. 20 %CdS/MIL-53(Fe/Mn) composites shown optimum photocatalytic CO₂ reduction activity. The XPS results shown the strong interaction between CdS and MIL-53(Fe/Mn). The EPR measure proved the carriers of CdS can be transferred to MIL-53(Fe/Mn) oxidation cluster by the oxo-Fe(III)/Fe(II) and oxo-Mn(II)/Mn(III) redox cycling, and the results also suggest the oxo-Fe(III) and oxo-Mn(II) were redox active sites. We believe the approach that bimetallic MOFs act as dual cocatalyst to improve the photocatalytic activity would open a new avenue for the separation efficiency of photo-generated charge carriers.