Engineering substitution position in cobalt phthalocyanines for enhanced activity and stability in CO2 electroreduction

Molecular catalysts have been explored for electrochemical CO 2 reduction (CO 2 RR) owing to their well-defined active sites, high product selectivity, and generally low cost. Moreover, their catalytic performance can be further improved by precisely tuning their electronic structure and mitigating the inherent structural flexibility of these molecular systems. In this work, substituent engineering is employed to modulate the electronic structure of cobalt phthalocyanine (CoPc) catalysts for CO 2 RR. Strong electron-donating methoxy-substituted CoPc catalysts with varied substitution positions were synthesized and evaluated using spectroscopic characterization, electrochemical measurements, and DFT calculations. These findings reveal that methoxy substitution modulates the electron density at the Co center and induces moderate molecular distortion, thereby promoting CO 2 adsorption by stabilizing key intermediates and suppressing the competing hydrogen evolution reaction. Notably, the para -methoxy substituted CoPc delivers the highest performance, achieving a CO Faradaic efficiency of 96% and a turnover frequency of 8.6 s −1 . It further sustains an FE CO above 80% during 120 h of continuous electrolysis, demonstrating markedly improved stability compared with unsubstituted CoPc. This work provides a facile molecular design strategy for tuning the substitution position of CoPc-based catalysts, offering valuable guidance for the development of efficient and stable CO 2 RR molecular systems.