Structurally Asymmetric Ni−O−Mn Node in Metal–Organic Layers on Carbon Nitride Support for CO₂ Photoreduction

The Jahn-Teller (J-T) effect-induced lattice distortion presents an advantageous approach to tailor the electronic structure and CO₂ adsorption properties of catalytic centers, consequently conferring desirable photocatalytic CO₂ reduction activity and selectivity. Nevertheless, achieving precise J-T distortion control over catalytic sites to enhance CO₂ adsorption/activation and target-product desorption remains a formidable challenge. In this work, we successfully induced J-T lattice distortion in neighboring Ni sites by exchanging high-spin Mn²⁺ into Ni-O-Ni nodes. EXAFS results and DFT simulations revealed that the highly asymmetric Ni-O-Mn nodes induced structural contraction (shortened Ni-O bonds) in the adjacent Ni-O lattice. The magnetic hysteresis loop (M-H) confirmed that the introduction of Mn²⁺ increased the number of spin electrons, thereby increasing the magnetization intensity. The spin mismatch between photogenerated electrons and holes suppressed charge recombination. Significantly, the d orbitals of the Ni sites in the Ni-O-Mn nodes exhibited strong orbital hybridization with the p orbitals of CO₂, as evidenced by the enhanced d-p orbital overlap, facilitating rapid CO₂ adsorption and activation. Consequently, the sample featuring lattice-mismatched Ni-O-Mn nodes exhibited an 8.79-fold enhancement in CO production rate compared to the Ni-O-Ni nodes, in the absence of cocatalysts and sacrificial reagents.