Metal-Salen metal organic framework supported single-metal site electrocatalysts for oxygen evolution reaction

Metal-organic frameworks (MOFs) are emerging as versatile platforms for supporting isolated single-site catalysts due to their privileged structural designability and uniformity, have received special attention in electrocatalytic applications. Herein, a novel pyrazole-type nickel (Ni)-Salen based MOF has been constructed via an incompletely linked self-assembled form, as determined by the single-crystal X-ray diffraction. The ring-opening tetradentate metal nitrogen‑oxygen (MN₂O₂) structure in above MOF features strong chelating coordination and accessible open metal sites, strongly implying its enormous potential as single-metal site electrocatalysts. The obtained Ni-Salen based MOF is then used to catalyze oxygen evolution reaction (OER), exhibiting superior catalytic performance than the pyrazole-type BUT-55 MOF without suspended metal sites. Notably, the nickel/iron (Ni/Fe)-Salen MOF can be constructed through partially replacing Ni with Fe, that has a higher OER activity over commercial ruthenium dioxide (RuO₂) and a good electrocatalytic stability over 40 h. The subsequent electrochemical property testing and density functional theory (DFT) calculations deepen the understanding of structure-activity relationships and reveal the thermodynamic rationale for the different catalytical performance of MOFs. This work pioneers the application of metal-Salen based MOFs in electrocatalysis, highlighting the advantages of strong chelating coordination and accessible open metal sites in metal-Salen MOF, providing new insights for designing MOFs with electrocatalytic capabilities.