Photoswitchable Transformation between Homogeneous and Heterogeneous Catalysis Enabled by Azobenzene-Functionalized...

The persistent challenge in catalysis lies in reconciling the high activity of homogeneous systems and the easy separation of heterogeneous catalysts. Inspired by biological photoadaptation, we report azobenzene-functionalized metal-organic polyhedra (MOPs) that achieve a photoswitchable transformation between homogeneous and heterogeneous catalysis via light-triggered trans-cis isomerization. The photoswitchable catalysts were fabricated by grafting azobenzene moieties on Rh₂ paddlewheel axial sites in RhMOP. Visible light stabilizes the trans isomer, yielding homogeneous catalysis through optimized solvation and weakened intermolecular forces, while UV-induced cis isomerization triggers a catalyst precipitate via unfavorable solvation and enhanced interactions. This phase switching creates a 52% yield differential in CO₂ cycloaddition with epichlorohydrin, governed by phase-dependent active site accessibility and different steric effects derived from isomerization. The catalyst retains activity over light-regulated cycles and adapts to diverse substrates and photoswitchable catalysts. This study may provide a promising approach to bridge the gap between homogeneous and heterogeneous catalysis.