Two-Dimensional Metal-Organic Framework (TM₃X₁₂C₂₄) as Promising Cathodes for Li-O₂ Batteries

Two-dimensional (2D) metal-organic frameworks (MOFs) have emerged as promising electrocatalysts for Li-O₂ batteries due to their tunable structures, high specific surface areas, and well-defined active sites. Herein, first-principles calculations combined with the computational hydrogen electrode model are systematically employed to investigate the structural stability, electronic properties, adsorption behaviors of Li_xO_y intermediates, and electrocatalytic mechanisms of 2D TM₃X₁₂C₂₄ MOFs (TM = Fe, Co; X = NH, O, S) for Li-O₂ battery reactions. The results show that the optimized 2D TM₃X₁₂C₂₄ MOFs exhibit atomically thin planar structures, where covalent bonds (C-C and C-N/O/S) and ionic bonds (TM-N/O/S) coexist, ensuring structural robustness. Electronic structure reveals that spin densities are mainly localized on Fe/Co centers. Fe-based MOFs display distinct magnetic properties, whereas Co-based MOFs exhibit varying electronic characteristics depending on the coordination environment. The adsorption strength of Li_xO_y intermediates follows a coordination-dependent trend. Thermodynamic free energy calculations demonstrate that the Fe-NH MOF possesses excellent thermal stability and the lowest discharge/charge overpotentials. Furthermore, the adsorption energy of LiO₂ could be identified as a key descriptor governing reaction activity. This work provides valuable mechanistic insights into how the coordination environment regulates the catalytic performance of 2D MOFs and offers a rational design strategy for high-performance Li-O₂ battery electrocatalysts.