Inhibiting Back‐Electron Transfer via an Organic–Inorganic D–A′–A Structure in Metal–Organic Frameworks for Redox‐Neutral Csp ² –Csp ² Coupling

Designing efficient photocatalytic structures for organic conversions has been a continuous endeavor, and one of the strategies is to focus on enhancing the availability of the photoinduced charge‐separated state of the catalyst. Inspired by the multilayer structures in Dye‐Sensitized Solar Cells (DSSCs), two isostructural crystalline metal–organic frameworks, TPPA–Cd–SiW ₁₂ and TPPA–Cd–SiV ₂ W ₁₀ , were developed, featuring a defined molecular organic–inorganic donor–acceptor′–acceptor structure on a rigid backbone, where the triphenylamine moiety acts as the electron donor ( D ), pyridyl groups as transient acceptors ( A′ ), and Keggin‐type polyoxometalates as terminal electron reservoirs ( A ). When applied to photoinduced redox‐neutral Csp ² –Csp ² coupling, these MOFs demonstrated a 200% maximum improvement in reaction rate constants compared to the free ligand. Experimental and computational mechanistic studies reveal that, upon UV irradiation, the initial charge separation within the organic ligand TPPA was followed by secondary electron transfer from the pyridyl groups of TPPA to neighboring polyoxometalates, thereby isolating the cationic and anionic centers, a mechanism parallel to that in DSSCs. This spatially separated D –A′ –A architecture effectively inhibits back‐electron transfer (BET), stabilizing the charge‐separated state and facilitating interaction between photoinduced redox centers and organic substrates. This D –A′ –A design strategy offers a robust platform for engineering charge separation in heterogeneous photocatalysis.