Substituent-Position-Dependent Electrochemical CO₂ Reduction Activity of Pb–S-Based Coordination Polymers

Shunta Iwamoto, Ryohei Akiyoshi, Sora Nakasone, Chomponoot Suppaso, Megumi Okazaki, Kazuhide Kamiya, Yuta Tsuji,* Daisuke Tanaka,* Kazuhiko Maeda*

Developing electrocatalysts for CO₂ reduction is essential for the effective use of renewable energy. Materials containing molecules such as coordination polymers have strong potential to exhibit high activity and selectivity. However, a critical shortcoming is that they often decompose into metals or metal oxides during reactions, thereby preventing the manifestation of functions unique to molecular structures. In this study, we compare a series of Pb–S-based coordination polymers, [Pb(x-SPhOMe)₂]_n (HSPhOMe = methoxybenzenethiol, x = ortho (KGF-32), meta (KGF-33), and para (KGF-34)), as model electrocatalysts to investigate the design guidelines. They have different crystal structures in terms of dimensionality and coordination environment. Among them, KGF-32 shows the highest Faradaic efficiency for formate production: 96.6 ± 2.9% at −1.0 V vs RHE with a partial current density of −9.76 ± 2.1 mA cm^–2. By contrast, KGF-33 and -34 show lower Faradaic efficiencies for formate production, along with more pronounced decomposition to PbCO₃. We use scanning electron microscopy, X-ray diffraction, and Raman spectroscopy to confirm that KGF-32 retains much of its crystal structure during operation, whereas KGF-33 and -34 decompose extensively. In addition, density functional theory calculations reveal that the energy barrier for formate production on KGF-32 is lower than that on PbCO₃, which explains its superior catalytic activity. Our work demonstrates the inherent advantages of coordination-polymer-based electrocatalysts and provides valuable guidelines for designing more efficient and stable systems for CO₂ reduction.

Chem. Mater. 2026, in press.