Confined CuI sites in partially electro-reduced 2D conductive Cu-MOF film for boosting CO2 electrocatalysis to C2 products

Cu-based catalysts, especially co-sites of Cu0 and CuI, are the best competitors for electrochemical CO2 fixation to produce multi-carbon (C2 + ) products. However, it is challenging to construct highly stable CuI sites due to the changeability of its valence state and electronic structure in the electroreduction process, and the mechanism is also elusive. Herein, a 2D conductive CuII-MOF film (CuIIHHTP@Cu0) is prepared on Cu (100) foil by in-situ electrochemical assembly. After pre-reduction, the in-situ produced Cu2O clusters are confined in the cavities of the film created by the local breaking of the MOF framework to construct a unique CuI-CuIIHHTP@Cu0 catalyst, so that a novel strategy is proposed to stablize highly dispersed CuI sites during electrochemical reduction, thus protecting the Cu2O clusters from further reduction and ensuring the coexistence of CuI (11 1)Cu0 (100) sites. As such, the current density of CO2 electrochemical reduction catalyzed by this catalyst exceeds 300 mA cm-2, the duration overs 50 h, and the C2 selectivity achieves 72.6 %. In-situ spectroscopy and theoretical calculations reveal that the optimized microenvironment of the CuI (1 1 1) sites reduces the energy barrier of *OCCOH coupling, and Cu0 (100) sites increase the coverage of *CO, thus boosting the production of C2 products.