Inner‐Axial Chlorine Engineering Enables Efficient and Selective Phenol Electrocatalytic Upcycling to Benzoquinone on Noble‐Metal‐Free Catalysts

Electrocatalytic upcycling of aqueous phenol into value-added para-benzoquinone (p-BQ) provides a promising route for synergistic wastewater treatment and sustainable chemical synthesis. Nevertheless, previous attempts have primarily relied on noble metal-based (e.g., Pd, Ru) electrocatalysts, but struggled with high costs and low selectivity. We, herein, report a noble-metal-free catalyst comprising carbon nanotube (CNT)-supported CoN₄ sites coordinated with inner-axial chloride atoms (Co-CNT-Cl), delivering 92.4% phenol conversion and 83.7% p-BQ yield under mild conditions. The superior electrocatalytic performance stems from inner-axial coordination of Cl, which fine-tunes the CoN₄ site microenvironment and electronic structure. This modification enhances charge-transfer capacity, optimizes oxidation thermodynamics, and facilitates phenol adsorption and p-BQ desorption. The proposed electrocatalytic system with the Co-CNT-Cl catalyst, maintains > 80.3% phenol conversion and > 70.7% p-BQ yield over 10 consecutive cycles. Furthermore, integrating the Co-CNT-Cl catalyst into a continuous-flow electrolyzer enables efficiently operational stability. This work establishes a potential and cost-effective electrocatalytic approach to valorize phenolic wastewater through resource recovery.