Microwave-assisted rapid synthesis and activation of ultrathin trimetal-organic framework nanosheets for efficient electrocatalytic oxygen evolution.

Ultrathin metal-organic frameworks (MOFs) nanosheets have been considered as one of promising electrocatalysts for oxygen evolution reaction due to their unique structures. However, the preparation process is subject to the low-yield exfoliation and time-consuming synthetic methods. And it still requires to be explored to develop an efficient strategy for regulation of surface electronic states of MOFs to enhance their electrocatalytic activities. Herein, we report a facile microwave-assisted synthesis of NiCoFe-based trimetallic metal-organic framework (MOF) nanosheets, which can achieve simultaneously rapid synthesis and activation of MOF for OER. The as-prepared Ni4Co4Fe2-MOF nanosheets exhibit excellent OER activity and electrochemical stability, which can deliver a current density of 10 mA cm-2 at a low overpotential of 243 mV with a small Tafel slope of 48.1 mV dec-1. This work provides a facile method for the rapid synthesis of MOF nanosheets and also demonstrates an effective approach for regulating the electronic structure of MOFs for electrocatalysis.

Ultrathin Trimetal-Organic Framework Nanosheet Electrocatalysts for the Highly Efficient Oxygen Evolution Reaction.

Synthesis of ultrathin metal-organic framework (MOF) nanosheets for highly efficient oxygen evolution reaction (OER) is prevalent, but still many challenges remain. Herein, a facile and efficient three-layer method is reported for the synthesis of NiCoFe-based trimetallic MOF nanosheets, which can be directly used for the oxygen evolution reaction in alkaline conditions. The physical characterization and morphology of trimetallic MOF nanosheets were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). By optimizing the molar ratio of Ni/Co/Fe atoms, a series of MOFs with different metal proportions were synthesized. Among them, the as-prepared (Ni3Co1)3Fe1-MOF nanosheets can deliver a current density of 10 mA cm-2 at a low overpotential of 245 mV with a small Tafel slope of 50.9 mV dec-1 in an alkaline electrolyte and exhibit excellent stability. More importantly, through the characterization of the intermediates in the OER process, the possible source of the catalytic active species is the electrochemically transformed metal hydroxides and oxyhydroxides.

Regulating Hydrogenation Chemoselectivity of α,ß-Unsaturated Aldehydes by Combination of Transfer and Catalytic Hydrogenation.

Two hydrogenation mechanisms, transfer and catalytic hydrogenation, were combined to achieve higher regulation of hydrogenation chemoselectivity of cinnamyl aldehydes. Transfer hydrogenation with ammonia borane exclusively reduced C=O bonds to get cinnamyl alcohol, and Pt-loaded metal-organic layers efficiently hydrogenated C=C bonds to synthesize phenyl propanol with almost 100 % conversion rate. The hydrogenation could be performed under mild conditions without external high-pressure hydrogen and was applicable to various α,ß-unsaturated aldehydes.