Light-Driven CO₂ Reduction over Prussian Blue Analogues as Heterogeneous Catalysts

The increase of carbon dioxide (CO₂) in the atmosphere has resulted in a global greenhouse effect and extreme weather. Photocatalytic conversion of CO₂ into valuable chemicals driven by solar energy is conceivable for solving the above problem. Metal–organic frameworks (MOFs) as a class of organic–inorganic hybrid materials have considerable prospect for carbon dioxide reduction reaction (CO₂RR) photocatalysis. Nevertheless, most MOFs in the CO₂RR still have limited photocatalytic performance as well as selectivity caused by having a single metal and face the challenge of instability. Herein, 10 Prussian blue analogues (PBAs) as heterogeneous catalysts were directly employed for the photocatalytic CO₂RR, which exhibit good photocatalytic performance for CO production. A mass evolution rate of 140 mmol g^–1 h^–1, an apparent quantum efficiency (AQY) of about 0.7%, and a selectivity of about 96.8% for CO were obtained over Ni–Co PBA. Notably, the CO₂RR activities of M^IICo PBAs are better than those of M^II–Fe PBAs, but the former’s selectivities for CO are lower than those of the latter. The divergence of activity is dependent on their electron transfer rates, which is confirmed by the electrochemical experiments and spectral characterization. In addition, density functional theory (DFT) as well as H₂ adsorption and desorption experiments of the PBAs reveal the difference in selectivity.