Elucidating the Effects of Electrolytes on a Robust MOF Interface for Enhanced CO₂ Electroreduction to C₂ Products

Elucidating the role of electrolytes in steering CO₂ electroreduction toward C₂₊ products is critical, yet impeded by dynamic electrocatalyst reconstruction during the CO₂RR. Herein, we successfully prepared a novel Cu-based metal-organic framework (Cu-BDP, BDP = 1,4-benzenedipyrazolate) with robust Cu-N₄ coordination. Bode phase analysis and contact angle measurements demonstrate that Cs⁺ cations facilitate interfacial charge transfer and establish local hydrophobic microenvironments to suppress hydrogen evolution reactions. Meanwhile, adsorbed I^-anions generate more accessible active sites. As a result, in the optimized CsI electrolyte, a high C₂ Faradaic efficiency of 50.34% is achieved at -1.6 V vs RHE. Density functional theory (DFT) calculations reveal that I^- anions preferentially facilitate initial CO₂ activation and stabilize single *CO intermediates, while Cs⁺ cations promote the enrichment of multi-CO intermediates and the hydrogenation of *OCCO to *OCCOH on the Cu-BDP surface. Furthermore, the synergistic effect of the Cs⁺/I^- binary electrolyte system significantly reduces the energy barrier for C-C coupling compared to electrolytes containing only Cs⁺ or I^- ions. This work provides insights into the synergistic effect of electrolyte cations and halide ions on CO₂ electroreduction.