Site-specific electronic sacrifice at a MOF-on-MOF-derived CoP/(CoFe)P2 heterointerface for oxygen evolution catalysis

The rational design of heterointerfaces is a potent strategy for optimizing the electronic structure of catalysts, yet achieving site-specific activation at the atomic level remains a formidable challenge. Nevertheless, most reported heterostructures suffer from ill-defined interfaces and non-specific activation, thereby obscuring structure-activity relationships and limiting mechanistic understanding. Herein, we propose a lattice-guided MOF-on-MOF strategy to fabricate an atomically precise CoP/(CoFe)P 2 interface embedded within an N-doped carbon matrix (CoP/(CoFe)P 2 -C). Specifically, the epitaxial growth of CoFe-PBA nanocubes on a MOF-274 template yields a MOF-274@PBA precursor with pre-organized metal domains, which are transformed into intimate phosphide heterojunctions during phosphidation. The optimized CoP/(CoFe)P 2 -C catalyst exhibits exceptional oxygen evolution reaction (OER) activity in alkaline media, requiring an overpotential of only 269 mV to reach 10 mA cm −2 , while demonstrating remarkable structural stability for over 60 h. Furthermore, density functional theory (DFT) calculations reveal that this superior performance stems from a site-specific electronic sacrifice mechanism. At the heterointerface, specific Co sites act as electronic buffers, sacrificially stabilizing unfavorable local configurations. This redistribution optimizes the electronic structure of adjacent Co and Fe sites, collectively lowering the kinetic barrier for *OOH formation and thus enhancing OER kinetics. This work establishes a controllable and generalizable strategy for constructing phosphide heterointerfaces with atomic-level precision, and provides fundamental mechanistic insights into the rational design of advanced OER electrocatalysts through site-specific electronic modulation.