Defects as catalytic sites for the oxygen evolution reaction in Earth-abundant MOF-74 revealed by DFT

Abstract

The oxygen evolution reaction (OER) is the bottleneck of hydrogen production via water splitting and using efficient electrocatalysts becomes paramount to render this process viable. Metal–organic framework (MOF) catalysts, which are porous solid materials at the frontier between homogeneous and heterogeneous catalysis, have emerged as promising candidates. Earth-abundant MOF-74 materials have recently shown great performance towards the OER, but the true nature of their active sites remains unclear. Here, we employ density functional theory (DFT + U) to elucidate the reaction mechanism and rationalize the electrocatalytic activity of Fe–MOF-74. Our results demonstrate that the open metal sites of the pristine catalyst do not promote the OER; instead, metal sites associated with defective structures do. This study provides new insights into guiding the rational synthesis and post-synthetic engineering of MOFs for electrocatalysis.