Chemical clipping-driven electronic structure modulation in bimetallic Fe/Ni-MOFs for enhanced oxygen evolution reaction

Abstract

Bond breaking has become an innovative approach for post-synthetic modification of pore structures in metal–organic frameworks, enabling the creation of pore environments that cannot be achieved through conventional methods. Herein, a series of hierarchical porous bimetallic MOF-based electrocatalysts were prepared through an advanced chemical clipping technique, involving the introduction of Fe and selective removal of Ni centers to tailor the porosity of the Ni-BTC frameworks (HP-Ni_x/Fe_100-x-BTC, BTC = 1,3,5-trimesic acid). By controlling the concentration of 2-methylimidazole, the crystallographic morphology of HP-Fe₅₀/Ni₅₀-BTC we precisely regulated, enabling the formation of complex polyhedral structures such as octahedra, truncated tetrahedra and regular tetrahedra. The electrocatalytic oxygen evolution efficiency was significantly increased and the current density was enhanced through structure modulation. The optimized HP-Fe₅₀/Ni₅₀-BTC-1 constructs achieved substantially lower OER overpotentials reached as low as 258 mV and Tafel slopes of 48.79 mV dec⁻¹. Additionally, these materials demonstrated robust stability, maintaining performance over 35 h under operational conditions. Furthermore, density functional theory (DFT) calculations reveal that the modulated d-band center of HP-Fe₅₀/Ni₅₀-BTC-1 directs the flow of electrons, resulting in the enhancement the rate-determining step, and improves the adsorption capacity for intermediates during the oxygen evolution reaction (OER). These findings underscore the transformative potential of precise molecular engineering in metal-organic frameworks, advancing the paradigm of catalyst design by enabling microstructural control to optimize electrochemical properties.