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The research and development of transition metal oxides based electrocatalysts with high activity and stability for both oxygen evolution reaction and hydrogen evolution reaction via a facile design strategy is of critical importance. Herein, we fulfill both significant oxygen evolution reaction and hydrogen evolution reaction improvement in activity by hierarchically nanostructured Ce-MnCo 2 O 4 prepared by an oxalate coprecipitation method and a followed calcination process. X-ray photoelectron spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy mappings analysis show that the hierarchically nanostructured Ce-MnCo 2 O 4 -3% sample is homogeneously modified by 1.49 wt % Ce with increased Co 3+ species. We suspect that the introduction of suitable Ce content into MnCo 2 O 4 facilitates the oxygen transfer and the formation of Co 3+ species, and modifies the local chemical binding, resulting in active performance for oxygen evolution reaction (390 mV at 10 mA•cm −2 and a Tafel slope of 125 mV•dec −1 ) in 1.0 M KOH solution. In addition, the Ce-MnCo 2 O 4 -3% sample also exhibits hydrogen evolution activity with overpotential of 389 mV at 10 mA•cm −2 and a Tafel slope of 96 mV• dec −1 , and relatively good long-time stability for 12 h.

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Efficient and stable photocatalysts for selective oxidative coupling of amines to imines are crucial to the conversion of sustainable solar energy to value-added chemical energy. In this work, UiO-66-NH 2 @ Au@COF core−shell nanocomposites with intercalated Au nanoparticles between the UiO-66-NH 2 core and the covalent-organic framework (COF) shell have been demonstrated to exhibit enhanced activity and stability for visible-light-driven aerobic selective oxidation of amines to imines. With optimized Au and two-dimensional π-conjugated COF content, the obtained UiO-66-NH 2 @Au 0.5 @COF1 photocatalyst exhibited the highest conversion of benzylamine with an imine yield of 66.9% for at least five cycles. It is revealed that the introduction of appropriate Au and COF could not only broaden the visible-light absorption band but also promote the separation of photoinduced charge carriers and enhance the photocatalytic performance. Furthermore, a rational mechanism was explored to elucidate the process of photocatalytic reaction. The intercalated Au nanoparticles with the localized surface plasmon resonance (LSPR) effect act as generators of hot electrons and also transfer channels for the photo-generated electrons from the COF shell to the UiO-66-NH 2 core. Importantly, the MOF@metal@COF photocatalysts might provide a promising strategy to construct photocatalysts with desirable activity and stability under visible-light illumination.