Co-Ligand-Induced Electronic Modulation Controls Substrate Adsorption and Selectivity in Biomass Electrooxidation.

The electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is often limited by competitive adsorption between HMF and surface-bound hydroxyl species (OHads), which governs both activity and selectivity, yet independent control over these interfacial adsorption processes remains a fundamental challenge. Here, we report a molecular design strategy that introduces distinct anionic co-ligands into Cu-based catalysts to modulate the electronic density of the metal center and, consequently, its interaction with both OHads and HMF. This approach enables differential tuning of competing adsorption processes on the same active sites, effectively reshaping their intrinsic coupling under fixed reaction conditions. As a result, the optimized catalyst achieves catalyst-controlled pathway selectivity together with efficient FDCA production, delivering a Faradaic efficiency of 99%, a selectivity of 98%, and a high partial current density of 351 mA cm-2 at 1.6 V vs. RHE. In situ attenuated total reflectance (ATR) infrared spectroscopy reveals distinct adsorption behaviors and reaction intermediates, providing molecular-level insight into the origin of selectivity. This work establishes co-ligand engineering as an effective strategy for precise interfacial adsorption control in electrocatalysis, enabling catalyst-controlled pathway selectivity beyond conventional regulation by pH and applied potential.