Coordination-Driven Highly Active Bi-(Et₃N)_0.3 for Selective Cleavage of Lignin C_β-O-4 Bond via Fluidized Electrocatalysis

The development of a mild and efficient electrocatalytic system for lignin depolymerization via selective cleavage of aryl ether bonds to produce high-value-added chemicals is highly attractive yet remains challenging. Herein, we report a crystalline phase reconstruction strategy for the synthesis of heterogeneous Bi-(Et₃N)_0.3 catalyst with rich defect sites and high-valence Bi species, which, when coupled with a fluidized phosphotungstic acid (HPW) electrolyte, achieves 100% conversion of the 2-phenoxy-1-phenylethanol model compound and a phenol yield of up to 60.7%. The Faraday efficiency (FE) reached 89.3%, outperforming existing state-of-the-art lignin electrocatalytic systems. Comprehensive in situ electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) results confirm that the high-valence Bi species is beneficial in promoting the rapid activation of the protons (H⁺), while the rich-defect sites derived from the crystal phase reconstruction between Bi-O and Bi-N-C coordination optimize the adsorption-activation of oxygen-containing intermediates. Moreover, the HPW electrolyte with a low dissociation energy barrier ensures an abundant proton supply, while the ion-rich groups ([PW₁₀^VIW₂^VO₄₀]⁵⁻) further induce the progression of the reaction. By manipulating the variation of current density, the dissociation efficiency of H⁺ and [PW₁₀^VIW₂^VO₄₀]⁵⁻ of HPW were modulated, enabling the controllable switching of the phenol generation pathway. Through the rational design of an efficient electrocatalytic system and the optimization of the electrolyte microenvironment, the targeted and efficient cleavage of lignin C_β-O-4 bonds has been achieved, enabling the production of high-value-added chemicals.