Promoting Carrier Separation in [W₁₀O₃₂]^4--Doped POM@MOF Composites for Photocatalytic Oxidative Coupling of Amines

The integration of polyoxometalates (POMs) into metal-organic frameworks (MOFs) to construct composite photocatalysts represents a promising strategy for organic synthesis. The photosensitive [W₁₀O₃₂]^4- clusters (noted as W₁₀) were assembled with the La-MOF framework at the molecular level, successfully constructing a series of W₁₀@MOF composites. These materials not only endow La-MOF with visible-light absorption capacity but, more importantly, significantly promote the separation and migration efficiency of photogenerated electron-hole pairs. In the photocatalytic amine oxidation coupling reaction, W₁₀@MOF-4, with the largest W₁₀ loading amount, exhibits excellent catalytic performance. Under mild conditions and without the need for an external oxidant, it achieves a benzylamine conversion rate of 98% and an imine selectivity of >99%, outperforming the single component and demonstrating a significant synergistic catalytic effect. Through systematic photoelectrochemical characterization, including photocurrent response, electrochemical impedance, and solid ultraviolet diffuse reflection analysis, it was confirmed that the introduction of W₁₀ effectively regulated the material's energy band structure and significantly enhanced the interface charge separation efficiency as an electron capture center, providing a key mechanism basis for its outstanding photocatalytic performance.