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Strategies for developing efficient energy conversion and storage devices that have been optimized by designing electrode materials is a critical challenge for researchers. Herein, we report the design and synthesis of a series of Co@NC trifunctional electrocatalysts derived from rationally designed cobalt-added anion MOF precursors and preliminarily reveal the relationship between the precursor and corresponding efficient electrocatalysts. Benefiting from the special composition of Co2+-doped anion MOFs involving Co2+ chelates as the Co2+ sources, the resulting CoT@NC electrocatalyst possesses abundant Co/Co–Nx/Co–Ox and multiple active nitrogen sites that are evenly distributed. As expected, the rich variety of active species and hierarchical pore structures endow CoT@NC with excellent performances toward ORR, HER, and OER, including a high half-wave potential value of 0.86 V for ORR and low overpotential values for OER (350 mV) and HER (209 mV) at 10 mA cm−2 in an alkaline solution. Moreover, we assembled a conventional Zn–air battery with CoT@NC as the air-cathode catalyst, which exhibited excellent rechargeable performance and ultrahigh durability. Moreover, CoT@NC coated on Ni foam was used as both anode and cathode for the overall water-splitting process, which needed a bias voltage of 1.70 V to achieve a current density of 10 mA cm−2. This study sheds light on the design, fabrication, and regulation of highly active cobalt-based electrocatalysts with abundant active sites and tunable pore structures for electrocatalysis and other applications. [ABSTRACT FROM AUTHOR]

Exploring efficient and stable oxygen evolution reaction (OER) catalysts with earth-abundant elements has been an urgent task in water splitting. Metal–organic frameworks (MOFs), possessing abundant active metal sites and tunable porous crystalline structures, are promising as OER catalysts. In this paper, a MOF based on benzotriazole-5-carboxylate (Co3-btca) that contains unsaturated coordinated metal centers and a 1D channel was selected to act as an OER catalyst. To optimize the OER performance, isostructural bimetallic and trimetallic frameworks were obtained by doping with Fe and/or Ni ions. The optimized Co2.36Fe0.19Ni0.45-btca possesses the lowest overpotential of 292 mV at 10 mA cm−2 and a small Tafel slope of 72.6 mV dec−1. The enhanced catalytic performance could be attributed to the synergistic effect between the unsaturated coordinated Co, Fe and Ni sites, which are beneficial for the nucleophilic attack of OH− forming adsorption intermediates. [ABSTRACT FROM AUTHOR]

The butterfly-like tetranuclear cobalt cluster based 3D MOF [Me2NH2][Co2(bptc)(μ3-OH)(H2O)2] (1) underwent a reversible thermally triggered single-crystal-to-single-crystal transformation via Co–Owater weakened intermediate 1a to produce a partly dehydrated phase [Me2NH2][Co2(bptc)(μ3-OH)(H2O)] (2), which was confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and IR spectroscopy. During the dehydration course, the local coordination environment of one Co2+ ion was changed from the saturated octahedron to a coordinately unsaturated square-pyramid, accompanied by a crystal color change from red to purple. Compared with pristine hydrated 1, dehydrated 2 exhibits highly efficient and recyclable catalytic activity for cyanosilylation of carbonyl compounds with a low catalyst loading of 0.1 mol% Co at room temperature under solvent-free conditions, which due to the open Co2+ sites as catalytically activated sites played a significant role in the heterogeneous catalytic process. [ABSTRACT FROM AUTHOR]