Polyoxometalates as Bifunctional Templates: Engineering Metal Oxides with Mesopores and Reactive Surface for Catalysis
Mesoporous metal oxides with optimized porosity and active surface usually exhibit unexpected performance in heterogeneous catalysis. However, sacrificial templates and complicated processes are generally required to direct mesopores. Herein, we discover the bifunctional templating talent of polyoxometalate (POM) for generating not only mesopores but also reactive surface into metal oxides, and a facile, recyclable, and general method is reported. By mechanochemically ion-sharing between metal salts and POM, metal precursors undergo pyrolysis around large POM clusters, which can incorporate abundant mesopores into metal oxides (e.g.,Co3O4, Fe3O4, NiO, La2O3, MnO2, CeO2, ZrO2, CuO) with ultrahigh specific surface areas (up to 210 m2/g) after simply recycled by water washing. Unexpectedly, the oxidative feature of POM naturally contributes to the formation of high valence metal cations on material surface. As an example, the Co3O4 sample with both mesopores and enriched surface Co3+ species was more active than Co3O4 derived from silica template (T100=200oC) and commercial Co3O4 (T100=250oC), in CO oxidation. The current strategy may provide a promising route for the commercialization of mesoporous metal oxide catalysts with preferred surface features.