Electrochemical-Chemical Cascade Catalysis for Green Synthesis of Phenols Over a Three-Dimensional Hexaazatrinaphthalene-Based Covalent Organic Framework.

Abstract

Phenols are essential intermediates widely used in chemical and pharmaceutical industries, yet conventional synthetic routes typically demand energy-intensive conditions and multi-step procedures. Herein, we report a green and efficient cascade strategy for phenol synthesis that integrates in situ electrochemical hydrogen peroxide (H2O2) generation with chemical oxidation of arylboronic acids using molecular oxygen under mild conditions. This approach demonstrates excellent functional-group tolerance and broad substrate scope (20 examples), achieving high conversion and selectivity without employing toxic solvents. A three-dimensional covalent organic framework (3D COF) with hexaazatrinaphthalene (HATN) building units and htp topology is designed as a robust electrocatalyst, delivering a remarkable H2O2 production rate of ∼7.0 mol gcat -1 h-1. Mechanistic studies reveal that the abundant nitrogen sites in the COF backbone act as hydrogen-bond acceptors, which facilitate proton transfer, promote a well-matched proton-coupled electron transfer (PCET) process, and stabilize the key *OOH intermediate, thereby collectively enhancing the selectivity and activity of the 2e- oxygen reduction reaction. Techno-economic (TEA) analysis further validates the potential economic feasibility of this integrated route based on laboratory scale. This work highlights the potential of rationally engineered 3D COFs to bridge electrosynthesis and synthetic chemistry, offering a mild and sustainable alternative to conventional energy-intensive phenols production.