Organic Molecule Functionalization Enables Selective Electrochemical Reduction of Dilute CO₂ Feedstock

The electrochemical conversion of low-concentration CO₂ feedstock to value-added chemicals and fuels is a promising pathway for achieving direct valorization of waste gas streams. However, this is challenging due to significant competition from the hydrogen evolution reaction (HER) and lowered CO₂ reduction (CO₂R) kinetics as compared to systems that employ pure CO₂. Here we show that terephthalic acid (TPA) functionalization can boost selectivity towards CO₂R and suppress HER over a range of catalysts including Bi, Cu and Zn. For instance, TPA functionalized Bi attained a formate Faradaic efficiency (FE_HCOO-) of 96.3 % at 300 mA cm^-2 with pure CO₂ feedstock. Density functional theory simulations indicate that this is because TPA functionalization modulates the binding energies of the key reaction intermediates *OCHO and *H. With low-concentration feedstock (15 % CO₂) at 100 mA cm^-2, we achieved a high FE_HCOO- of 85.8 %, which was double that of an unmodified Bi catalyst. Using an electrolyzer with a porous solid electrolyte layer, we successfully showcase 30 h of continuous high-purity formic acid production with a 5 % CO₂ feed. Taken together, our findings demonstrate that molecular tuning of a catalyst can be an effective strategy for enabling selective CO₂R using low-concentration feedstock.