The discovery of efficient catalysts with suitable electronic states for CO₂ activation is critical for advancing CO₂ electrochemical reduction (CO₂ER). However, due to chemical inertness of CO₂, seldom materials exhibit such characteristics without modification. Herein, we employ density functional theory (DFT) computations to demonstrate that an intrinsic antiferromagnetic Mn₂B₇ monolayer characterized by alternating spin alignment prevents the complete filling of either spin-up or spin-down orbitals. This unique electronic structure provides unpaired ${\mathrm{d}}_{z^2}$ electrons to activate CO₂ and facilitate its conversion. As a result, Mn₂B₇ monolayer exhibits superior catalytic selectivity toward CH₄ and CH₃CH₂OH production, with low limiting potentials (−0.43 and −0.45 V) and kinetic energy barriers (< 1.0 eV), significantly outperforming nonmagnetic Fe₂B₇, Ru₂B₇, and Os₂B₇ monolayers. This study demonstrates the crucial role of adjacent antiferromagnetic unpaired ${\mathrm{d}}_{z^2}$ electrons in CO₂ adsorption, activation, and conversion, providing new insights into the design of highly efficient CO₂ER catalysts.