Rh ⁰ –Rh ^δ+ Synergy Enables Hydroxyl‐Directed Electrocatalytic Hydrogenation of Guaiacol

ABSTRACT

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 Rh ⁰ –Rh ⁰ sites generally activate guaiacol through Rh ⁰ ‐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 Rh ⁰ and Rh ^δ+ sites (Rh ⁰ –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 Rh ⁰ sites, thereby promoting d→π* back‐donation and lowering the hydrogenation barrier. The resultant Rh ⁰ –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 Rh ⁰ –Rh ⁰ . 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.