Atomic Layer Infiltration Enabled Cu Coordination Environment Construction for Enhanced Electrochemical CO₂ Reduction Selectivity: Case Study of a Cu Metal–Organic Framework

Cu-based materials are promising catalysts for the electrochemical CO2 reduction reaction (CO2RR). However, they frequently have a low Faradaic efficiency (FE) and selectivity for a specific single product. Particularly, the precise construction of a Cu microenvironment is a great challenge in the design and fabrication of excellent Cu-based CO2RR catalysts. In order to systematically regulate the Cu metal site environment, the classic HKUST-1 containing paddle-wheel Cu coordination nodes was used as a template and modified with the atomic layer infiltration (ALI) technique in this work. A detailed structural analysis shows that a uniform distribution of Zn–O–Zn sites is introduced into HKUST-1 and linked to neighboring Cu nodes without changing the original morphology and structure. In comparison with pristine HKUST-1, the FE for CO increases from 20–30% to 70–80% for the ALI-modified HKUST-1 within the tested overpotential range. Density functional theory (DFT) simulations prove that the modification with Zn–O–Zn by ALI enhances the adsorption enthalpy of CO2 and strengthens the bonding interaction between the COOH* intermediate and the adsorption center, thereby reducing the whole reaction barrier and accelerating CO formation. The proposed ALI technique elucidates the reliance of CO2RR selectivity on the Cu microenvironment and provides a platform for regulating the coordination environments of Cu or other metal-based electrocatalysts to facilitate the high selectivity of CO2RR in the future.