Optimized Ternary PdCuFe Prussian Blue Analogues for Selective Photocatalytic Conversion of CO2 to CO

Abstract

Photocatalytic CO₂ reduction is hindered by the rigid coordination environments of conventional catalysts, which limit coordinatively unsaturated sites (CUSs), suppress charge transfer, and reduce CO₂ binding affinity. Prussian blue analogues (PBAs) offer porous structures and stability, but traditional bimetallic PBAs retain these drawbacks. We introduce Pd²⁺ into a Cu−Fe cyanide PBA lattice, forming a ternary PdCuFe PBA with high-density CUSs. In this design, Pd sites stabilize ^*COOH intermediates, Cu sites function as electron reservoirs, and the Fe−CN framework ensures structural integrity. Under visible light without sacrificial agents, the PdCuFe PBA exhibits enhanced CO₂ reduction performance, outperforming CuFe and FeFe PBAs by factors of 1.77 and 4.10, respectively. In situ DRIFTS and DFT calculations reveal that Pd incorporation extends light absorption and lowers the ^*COOH formation energy barrier. This work presents a strategy for designing multimetallic photocatalysts rich in unsaturated active sites for sustainable solar fuel production.