Photoswitchable Transformation between Homogeneous and Heterogeneous Catalysis Enabled by Azobenzene-Functionalized Metal–Organic Polyhedra

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.