# Manipulating Spin States by Metal Axial Coordination of Active Sites for Generating Valuable CH4 in CO2 Reduction

## TL;DR

This paper shows how manipulating metal coordination in catalysts can improve CO2 reduction to produce methane.

## Contribution

A new spin-state manipulation strategy is introduced to enhance CO2 reduction for methane generation.

## Key findings

- Ni axial coordination induces a spin-state transition in Mn, improving CO2 reduction activity.
- The Mn d-band center shifts toward the Fermi level, strengthening *CO adsorption.
- This leads to efficient eight-electron processes for CH4 production.

## Abstract

Dual‐atom catalysts (DACs) exhibit superior catalytic performance with more active sites and diverse electronic structures. However, electronic spin state as the crucial factor is rarely explicitly studied, and the in‐depth understanding of the electronic structures remains a great challenge. Herein, double‐solvent method is adopted to encapsulate the Ni and Mn ions into the channels of Mn‐based ZIF ‐8 (Ni→Mn DAC) and Ni‐based ZIF ‐8 (Mn→Ni DAC), respectively. The introduced metal exhibits axial coordination around the metal active site with the distinct coordination environments, indicating the diverse electronic structures. Experimental investigations and theoretical calculations demonstrate that the improved CO2 reduction (CO2RR) activity of Ni→Mn DAC derives from the axial coordinated Ni atom‐induced spin‐state transition of Mn 3d
3 from low‐spin (dxy
↑↓ dz
2
↑) to high‐spin (dxy
↑ dxz
↑ dyz
↑). This is attributed to the splitting of Mn 3d orbital with specific C─Ni─N─Mn─N3 coordination structure, which makes Mn d‐band center push toward the Fermi level and further strengthens the adsorption of *CO. Based on the accelerated reaction kinetics, the strong interaction between Mn active sites and *CO leads to the rapidly completion eight‐electron process for generating CH4. This work provides an efficient spin‐manipulation strategy for accelerating the generation of valuable CH4.

By encapsulating Ni atoms into Mn zeolitic imidazolate framework‐8, the spin‐state transition of Mn 3d
3 from low‐spin to high‐spin was facilitated upon Ni axial coordination via Mn 3d orbital splitting. This facilitates the electronic donation and induces the closing of Mn d‐band center toward Fermi level to strengthen *CO adsorption, thereby generating valuable CH4 in CO2 reduction reaction.