Steering CO2 electroreduction toward C2+products by defect-engineered coordination microenvironments of Cu-MOFs

Electrocatalytic CO2 reduction reaction (CO2RR) presents a promising strategy to alleviate energy and environmental crisis, where upgrading CO2 into multicarbon (C2+) chemicals is greatly favored. Cu-based catalysts have been showing attractive potential for C2+ production and yet remain to achieve advanced performances and clarify actual mechanisms. Herein, defect-engineered Cu-based metal-organic frameworks (MOFs) with missing linkers (UC-Cu-BTEC) are constructed as electrocatalysts for CO2RR. The presence of linker vacancies leads to distorted Cu dimers and undercoordinated Cu ions, demonstrating a feasible strategy to regulate the local atomic structure, bonding features and electronic configurations of active sites. The Faradaic efficiency of C2+ on UC-CuBTEC reaches 77.2 % and maintains above 70 % within a wide potential window of 400 mV, far beyond that of pristine MOFs. The partial current density of C2+ under neutral conditions in a flow cell amounts to -153.5 mA cm- 2. By in situ X-ray absorption spectroscopy and Raman spectroscopy, it is unveiled that abundant undercoordinated Cu species have been generated by the reconstruction of defective Cu dimers during CO2RR, which improves *CO coverage and stabilizes C2 intermediates, thus promoting C-C coupling and enhancing the CO2-toC2+ performance. This work sheds new light on engineering the coordination microenvironments of active sites and designing defective MOFs for tailored functions.