Defect-confined iridium single atoms in bimetallic–organic frameworks for efficient CO₂ photoreduction

Single-atom catalysts (SACs) have emerged as promising candidates for CO₂ conversion. However, their catalytic activity is hindered by low metal loading, insufficient accessibility, and non-uniform dispersion. Herein, we present a novel “defect capture and confined reduction” strategy to achieve the uniform dispersion of high-loading Ir single atoms in a Ti-Mn-metal–organic framework (Ti-Mn-MOF). The defective Ti-Mn-MOF induced by in-situ etching of Mn²⁺ species enabled the efficient single-atom anchoring, while the robust Ti–O bonds provided high structural integrity. The intrinsic MOF cavities offered spatial confinement to suppress atom aggregation. This approach demonstrates broad applicability for incorporating various metal single atoms. Under visible light irradiation, Ir/Ti-Mn-MOF delivered a remarkably high CO evolution rate of 30.1 μmol·g⁻¹·h⁻¹ in gas–solid CO₂–H₂O photocatalytic system, outperforming most reported photocatalysts. The incorporation of Ir single atoms led to the formation of a unique bridging Ir–*COHO*–Mn structure, which stabilized the *COOH intermediate and significantly reduced the reaction energy barrier, resulting in superior photocatalytic performance. This work establishes a versatile route for constructing high-loading SACs and offers valuable insights into the rational design of efficient photocatalysts for CO₂ reduction.