Charge‐Density‐Mediated Mitigation of Jahn–Teller Effect for Boosting CO ₂ Photoreduction in a Self‐Assembly Metal–Organic Layer

Abstract Precisely tailoring the electronic effect of catalytic sites remains a fundamental challenge in the field of artificial photosynthesis. Particularly, the strategies for regulating orbital and electronic state via the Jahn–Teller (J–T) effect at the atomic level for boosting CO 2 photoreduction remain rarely investigated. Herein, a rational mitigation strategy is demonstrated via a single‐atom modification in metal‒organic assemblies which enables precise control over the J–T effect and thereby regulates the electron density at the locally catalytic Fe sites. Through rational ligand design, a nanolayer ( 1 ) exhibiting mitigated J–T distortion and a nanoribbon ( 2 ) with pronounced J–T distortion are synthesized. Remarkably, the photocatalyst 1 achieves a more rapid CO production rate of 10.91 mmol g −1 h −1 under visible light, nearly double that of 2 (6.19 mmol g −1 h −1 ). A combination of experimental analyses, including single‐crystal X‐ray diffraction, XPS, magnetic susceptibility, and in situ DRIFTS, as well as DFT calculations, reveals that the mitigation of the J–T effect noticeably enhances the charge density at the Fe active sites, which boosts CO 2 adsorption and activation, and ultimately promotes CO generation. This work demonstrates the prominence of the J–T engineering photocatalysts and highlights the potential of regulating orbital and electronic degeneracies for boosting artificial photosynthesis.