Rh⁰-Rh^δ+ Synergy Enables Hydroxyl-Directed Electrocatalytic Hydrogenation of Guaiacol

Electrocatalytic hydrogenation (ECH) of lignin-derived guaiacol offers an appealing route toward sustainable chemical production but is impeded by the exceptional stability of aromatic rings. Conventional rhodium catalysts with electronically symmetric Rh⁰-Rh⁰ sites generally activate guaiacol through Rh⁰-arene π interactions. However, the induced electronic perturbation remains largely delocalized over the arene π system, resulting in only limited local polarization and sluggish dearomatizing hydrogenation kinetics. Here, we introduce a hydroxyl-directed activation strategy that exploits the phenolic hydroxyl group as an intrinsic handle for aromatic-ring activation. Spatially adjacent Rh⁰ and Rh^δ+ sites (Rh⁰-Rh^δ+) were constructed in RhO_x clusters through lattice-oxygen-mediated electrochemical reconstruction. The electron-deficient Rh^δ+ sites selectively anchor the phenolic hydroxyl group, perturbing resonance donation from the phenolic oxygen into the aromatic ring and inducing asymmetric redistribution of aromatic π-electron density. This hydroxyl-directed adsorption simultaneously orients the aromatic ring toward neighboring Rh⁰ sites, thereby promoting d→π* back-donation and lowering the hydrogenation barrier. The resultant Rh⁰-Rh^δ+ catalyst achieves a 2-methoxycyclohexanol production rate of 197.51 mmol h^-1 g_Rh ^-1, which is 22-fold higher than that of Rh⁰-Rh⁰. Our findings establish hydroxyl-directed aromatic-ring activation as an effective strategy for overcoming aromatic inertia, providing a design principle for the electrocatalytic upgrading of lignin-derived aromatics.