Efficient Electrocatalytic Water Oxidation by Fe(salen)–MOF Composite: Effect of Modified Microenvironment

An efficient and robust heterogeneous electrocatalyst, FSWZ-8 ((Fe-(salen)(OH) + H4[SiW12O40]·HCl)@ZIF-8) for oxygen evolution reaction (OER) at the neutral pH, was developed by coencapsulation of Fe-salen (i.e., Fe(salen)Cl) and SiW12 (i.e., H4[SiW12O40]) inside the cavity of zeolitic imidazolate framework-8 (ZIF-8) material by an in situ synthesis. Here ZIF-8 functions as a host, Fe-salen as the active catalyst, and SiW12 helps in the charge transport by lowering the overall electrical resistance of the resulting composite system. High turnover frequency (∼5 s–1) and high Faradaic efficiency (∼94%) make the concerned composite an efficient catalyst toward water oxidation. This is the first report of one of the simplest known metal complexes, Fe-salen, to perfrom electrocatalytic OER as a heterogeneous catalyst in the neutral pH. This work also highlights the benefits of coencapsulation of the Keggin polyoxometalate (POM) along with the active catalyst Fe-salen species. Encapsulation of SiW12 results in ...