Metal-Organic Frameworks Integrate Cu Photosensitizers and Secondary Building Unit-Supported Fe Catalysts for Photocatalytic Hydrogen Evolution

We report here the synthesis of a series of metal-organic frameworks (MOFs), FeX@Zr-6-Cu, comprising cuprous photosensitizing linkers (Cu-PSs) and catalytically active Fe-II centers supported on secondary building units (SBUs) for photocatalytic H-2 evolution. Close proximity (similar to 1 nm) between Cu-PS and SBU-supported Fe sites and stabilization of Fe sites by periodically ordered SBUs led to exceptionally high H-2 evolution activity for FeX@Zr-6-Cu, with turnover numbers of up to 33 700 and turnover frequencies of up to 880 h(-1). Photocatalytic H-2 evolution activities of FeX@Zr-6-Cu correlate with the lability of X counteranions, suggesting that open coordination environments of Fe sites generated by labile X groups facilitate the formation of Fe-hydride intermediates before hydrogen evolution. This work highlights the potential of using MOFs to integrate Earth-abundant components for solar energy utilization.