Engineering Copper‐Based Covalent Organic Framework Microenvironments to Enable Efficient CO 2 Electroreduction with Tunable Ethylene/Methane Switch

Abstract A microenvironment engineering strategy has been developed to switch the CO 2 electroreduction reaction (CO 2 RR) selectivity from methane (CH 4 ) to ethylene (C 2 H 4 ) by adjusting the coordination microstructures of trinuclear copper cluster‐based metal‐covalent organic framework (MCOF). When Cu sites are oriented to channels in Cu‐PyCA‐MCOF, methane is the main product. Conversely, when trinuclear copper sites are coordinated with OH − and H 2 O molecules in Cu‐PyCAOH‐MCOF nanosheets, the main product switches from CH 4 to C 2 H 4 with 50.5% selectivity and 200.2 mA cm − partial current density at −1.2 V (vs RHE). This happens because CO 2 molecules can only contact active sites perpendicular to the trinuclear copper cluster plane in Cu‐PyCAOH‐MCOF nanosheets, where the Cu─Cu distance between them is 3.2 Å, favoring the efficient conversion of CO 2 to C 2 H 4 through the C─C coupling reaction. Operando infrared spectroscopy, in situ X‐ray absorption near‐edge structure spectra, and DFT calculations reveal that changing the coordination environments of MCOFs significantly stabilizes key intermediates and reduces the energies of the CO 2 RR. This work offers an effective strategy for enhancing CO 2 RR performance toward C 2 H 4 products by tuning the microenvironments of copper‐based electrocatalysts.