Atmosphere-Directed Reconstruction of Cu-based Metal-Organic Frameworks toward Efficient CO2 Electroreduction

Abstract

The electrochemical reconstruction of metal-organic frameworks (MOFs) offers a promising approach for in situ fabrication of high-performance electrocatalysts. However, this innovation is often hindered by unpredictable structural transformations due to the complex thermodynamic and kinetic interplay of such multiple electrochemical and chemical processes. Herein, the reaction-atmosphere (Ar or CO2) guided reconstruction of Cu-based MOFs to Cu nanoparticles with mix-valence surface/interfaces was for the first time investigated to unravel the kinetic contribution made by intermediate chemisorption. As shown, Cu-1,3,5-benzenetricarboxylate (HKUST-1) with frangible Cu-O4 nodes undergoes thermodynamically favored reduction quickly upon applying cathodic potentials, followed by the varied surface changes kinetically governed by the intermediates of hydrogen evolution or CO2 reduction reactions (HER or CO2RR). Under an Ar atmosphere, the predominant HER increases the [OH-] of the microenvironment near cathodes and thereby boosts the re-oxidation of in-situ formed Cu toward Cu/Cu2O interfaces. Conversely, the CO2RR facilitates the strong adsorption of *CO on Cu surfaces, effectively preserving Cu(0) species. Thanks to the rich Cu/Cu2O interfaces with the lowered energy barrier for *CO-*CO coupling during the subsequent CO2RR test, the restructured electrocatalysts under Ar affords the obviously improved CO2-to-C2H4 conversion as compared with the counterpart restructured under CO2. Such atmosphere-controlled reconstruction strategy is further validated using CuBDC (BDC = 1,4-benzenedicarboxylate) with labile Cu-O4 nodes, while CuPz2 (Pz = pyrazole) with robust Cu-N4 coordination remains stable, highlighting the framework-dependent nature. These findings establish atmosphere-controlled reconstruction of metastable MOFs as a powerful tool for rational electrocatalyst design.