Post-synthetic exchange (PSE) of UiO-67 frameworks with Ru/Rh half-sandwich units for visible-light-driven H2 evolution and CO2 reduction

Abstract

Electron-deficient Ru/Rh half-sandwich units are optoelectronical, stereochemical, and redox and catalytically active in nature. Four different species of these units were designed and successfully incorporated into UiO-67 frameworks by post-synthetic exchange (PSE) method and employed for photocatalytic H₂ evolution and CO₂ reduction. Among them, the PSE-MOF catalysts containing [M–OH₂] (M = Rh or Ru) groups show higher photocatalytic activity than those with [M–Cl], providing a new example of the exploitation of H₂O molecules as small ancillary ligands for the construction of Ru/Rh half-sandwich units and subsequent incorporation into MOFs as photocatalytic centers. The application of TEOA (triethanolamine) and DMA (N,N-dimethylaniline) as sacrificial agents leads to different catalytic mechanisms and durations. A long-term hydrogen evolution lasting for 174 h without significant decrease in efficiency was achieved in the RhOH₂@UiO-DMA system, showing the advantage of PSE-MOFs as highly stable photocatalytic platforms with superior self-protective properties.