Carbon dioxide (CO₂) is the most notorious greenhouse gas, released by both natural and artificial processes. In an ideal scenario, the production and consumption of CO₂ should be balanced so that the concentration of CO₂ in atmosphere remains constant to maintain environmental stability. Unfortunately, with the intensification of human industrial activities, this balance has gradually been disrupted, leading to more CO₂ production and making global warming a pressing issue. With carbon neutrality gaining increasing attention, electrochemical CO₂ reduction reaction (CO₂RR) has emerged as a research orientation which converts CO₂ to value-added products while storing renewable energy. Cu-based electrocatalysts have been studied extensively for the CO₂RR into hydrocarbons in aqueous solutions under environmental conditions. However, they frequently endure low Faradaic Efficiency (FE) and selectivity of specific single product. Particularly, precise construction of Cu micro-environment is of great challenge for the design and fabrication of excellent Cu-based CO₂RR catalysts.

Atomic layer infiltration (ALI) allows gas phase precursors to penetrate and diffuse into porous substrates through their nanoporous structures and to grow within the subsurface. Aiming at systematically regulating the Cu metal site micro-environment, porous HKUST-1 containing paddle-wheel Cu coordination nodes was chosen as a template and modified with ALI technique in this work. Various metals were introduced into HKUST-1 using ALI method to construct bimetallic sites which tended to produce CO, HCOOH and other products with high FEs. Density Functional Theory (DFT) calculations prove the modification with metals by ALI enhances the adsorption enthalpy of CO₂ and alters the bonding interaction between reaction intermediates and adsorption center, thereby changing the reaction pathways. MOF conversion technique based on atomic layer deposition (ALD) will be utilized to fabricate HKUST-1 thin film in our future work, which allows nanometer precision of catalyst loading to balance active-site density with mass/charge transfer. The proposed ALI and ALD techniques elucidate the reliance of CO₂RR selectivity on the Cu micro-environment and provide a platform for regulating Cu or other metal-base electrocatalyst coordination environment to facilitate high selectivity of CO₂RR in the future