Engineering CO ₂ Pre‐Activation in In‐MOF for Enhancing its Electroreduction Activity

ABSTRACT The efficiency of electrocatalytic CO ₂ reduction (ECR) is largely governed by the adsorption of CO ₂ , a step often accompanied by pre‐activation via molecular bending and electron redistribution before the first electron transfer occurs. However, the explicit correlation between the extent of CO ₂ pre‐activation and the resultant reaction performance remains elusive due to the lack of direct structural evidence. Herein, we employ two In‐MOFs, FJU‐350 and FJU‐351, as crystalline model catalysts to visualize distinct CO ₂ pre‐activation configurations and unravel their critical role in ECR. FJU‐350 exhibits superior ECR performance with FE _formate of 90.9% at −1.4 V (vs. RHE), outperforming FJU‐351 (88.6% at −1.6 V). Single‐crystal X‐ray diffraction analyses indicate that this 200 mV efficiency gain is the consequence of their distinct structural microenvironments. FJU‐350 features a polarized carboxyl‐oxygen site, stabilizing a uniquely bent CO ₂ species (127.2°) via single‐site interaction, indicative of pronounced pre‐activation. Theoretical calculations confirm that the highly distorted configuration facilitates charge transfer and lowers the energy barrier. In contrast, FJU‐351 lacks such a directed site, accommodating near‐linear CO ₂ (≥153.3°) via delocalized π‐interactions. This work reveals a correlation between the pre‐activated CO ₂ configuration and its electroreduction performance, providing a strategic foundation for designing efficient catalysts through precise micro‐environment engineering.