Electrochemical CO₂ reduction reaction in aqueous electrolytes is a promising route to produce added-value chemicals and decrease carbon emissions. However, even in Gas-Diffusion Electrode devices, low aqueous CO₂ solubility limits catalysis rate and selectivity. Here, we demonstrate that when assembled over a heterogeneous electrocatalyst, a film of nitrile-modified Metal-Organic Framework (MOF) acts as a remarkable CO₂-solvation layer that increases its local concentration by ~27-fold compared to bulk electrolyte, reaching 0.82 M. When mounted on a Bi catalyst in a Gas Diffusion Electrode, the MOF drastically improves CO₂-to-HCOOH conversion, reaching above 90% selectivity and partial HCOOH currents of 166 mA/cm² (at −0.9 V vs RHE). The MOF also facilitates catalysis through stabilization of reaction intermediates, as identified by operando infrared spectroscopy and Density Functional Theory. Hence, the presented strategy provides new molecular means to enhance heterogeneous electrochemical CO₂ reduction reaction, leading it closer to the requirements for practical implementation.

水性电解质中的电化学CO ₂还原反应是生产高附加值化学品和减少碳排放的一条有前途的途径。然而，即使在气体扩散电极装置中，低CO ₂水溶液溶解度也限制了催化速率和选择性。在这里，我们证明，当在非均相电催化剂上组装时，腈改性金属有机框架（MOF）薄膜可充当显着的CO ₂溶剂化层，与本体电解质相比，其局部浓度增加约27倍，达到0.82 M。当安装在气体扩散电极中的 Bi 催化剂上时，MOF 极大地提高了 CO ₂到 HCOOH 的转化率，达到 90% 以上的选择性和 166 mA/cm ²的部分 HCOOH 电流（相对于 RHE 为 -0.9 V） 。正如操作红外光谱和密度泛函理论所证实的那样，MOF 还通过稳定反应中间体来促进催化。因此，该策略为增强非均相电化学CO ₂还原反应提供了新的分子手段，使其更接近实际实施的要求。