Evolving metal-organic frameworks for highly active oxygen evolution

Metal-organic frameworks (MOFs) as oxygen evolution reaction (OER) electrocatalysts in water have exhibited promising catalytic activity thanks to abundant reaction sites and great tunability. Generally, metal centers in MOFs are known to experience geometric and electronic changes to form catalytically active sites in the OER process. However, the in situ restructuring process of metal centers in MOFs is largely hindered by the intrinsic drawbacks of MOFs, such as low electrical conductivity, scarce coordinatively unsaturated metal nodes, and redox-inert linkers. Many strategies have been attempted to tune the geometric and electronic features of metal centers in pristine MOFs to refine the restructuring of metal centers. Clearly, an in-depth understanding of the structural correlation between the restructuring process and pristine MOFs becomes a prerequisite for obtaining highly active OER catalysts. In this perspective, we summarize the four essential design strategies of MOFs, including modulating morphologies, defects, metal nodes, and organic linkers of MOFs. We deduce that these strategies efficiently optimize the geometric and electronic structures of metal centers in MOFs, such as undercoordinated environments, coordination bond strengths, and the density of electronic states near the Fermi level, which facilitate the reconfiguration process of metal centers under operating conditions. This perspective offers a deep understanding of the restructuring process of MOFs during the OER process, which will lay the foundation for designing MOF electrocatalysts with high activity.