Electronic properties and ORR/OER catalytic activity of MOF-74 metal-organic frameworks: A theoretical study

Abstract

The electronic properties and catalytic activity for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of the metal–organic frameworks $M$$M$-MOF-74, where $M$$M$ = Cr, Mn, Fe, Co, Ni, and Cu, were investigated using density functional theory calculations. The ORR/OER activity was assessed by evaluating the adsorption free energy of reaction intermediates on the metal centers, following the computational hydrogen electrode method. Our findings reveal that all $M$$M$-MOF-74 structures exhibit band gap energies of approximately 2 eV and high-spin magnetic moments per metal atom with a ferromagnetic ground state. In terms of catalytic performance, Cr-MOF-74 and Fe-MOF-74 show outstanding ORR activity, with overpotentials around 0.5 V. Notably, Mn-MOF-74 and Ni-MOF-74 exhibit bifunctional ORR/OER activity, meaning they can catalyze both reactions simultaneously, with similar overpotentials of approximately 0.7 V. These ORR and OER overpotentials are comparable to those found on Pt(111) and IrO${}_2$${}_2$(110) surfaces, which are the most effective commercial electrocatalysts for the respective reactions. Additionally, the ORR/OER performance of $M$$M$-MOF-74 is analyzed using catalytic descriptors, providing deeper insights into its electronic structure and the adsorption behavior of reaction intermediates.