The in-depth exploration of electronic structure serves as a cornerstone for rational catalyst design, which is essential to unlock the precise structure-activity relationships governing heterogeneous CO₂ hydrogenation to formic acid. Herein, we report a coordination engineering strategy to tailor the electronic structure of iridium single-atom sites by synthesizing a series of Ir–N_x catalysts with well-defined N-coordination numbers (x = 4, 3, 2). Significantly, the optimized Ir–N₂ catalyst exhibits exceptional activity, achieving a high turnover number (TON) of 19,400, significantly surpassing most reported heterogeneous catalysts. Combined X-ray absorption fine structure (XAFS) analysis and density functional theory (DFT) calculations reveal that the reduced coordination in Ir–N₂ sites optimizes the local electron density, resulting in enhanced d-band charge occupancy and an upshifted d-band center. This favorable electronic structure facilitates reactant activation and stabilizes key intermediates, thereby lowering the overall energy barrier of the reaction. This work establishes a direct correlation between coordination geometry and catalytic performance through electronic modulation, offering a generalizable design principle for high-performance single-atom catalysts in CO₂ conversion.
This work entitled “Coordination engineering directs d-band center optimization for efficient CO₂ hydrogenation to formic acid on Ir–N_x single-atom catalysts” was published in Advanced Powder Materials (available online on 1 July 2026).
DOI: 10.1016/j.apmate.2026.100449