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Two novel polyoxometalate (POM)-based metal-organic frameworks (MOFs), [TBA]3[ε-PMo(V)8Mo(VI)4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA(+) = tetrabutylammonium ion) and [TBA]3[ε-PMo(V)8Mo(VI)4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1'-biphenyl]-3,4',5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA(+) ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of ε(trim)(4/3), NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials. It shows an onset overpotential of 180 mV and a Tafel slope of 96 mV·dec(-1), and the catalytic current density can approach 10 mA·cm(-2) at an overpotential of 237 mV. Moreover, NENU-500 and NENU-501 maintain their electrocatalytic activities after 2000 cycles.

Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe2O4 (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed show the 3D net-like textural structures of the electrospun spinel-type MFe2O4 NFs. In particular, the resulting MFe2O4 NFs have lengths up to several dozens of micrometers with an average diameter size of about 150 nm and possess abundant micro/meso/macropores on both the surface and within the films. The hierarchically porous structures and high surface areas of these MFe2O4 NFs (for example, the CoFe2O4 NFs possess a larger BET specific surface area (61.48 m(2) g(-1)) than those of the CoFe2O4 NPs (5.93 m(2) g(-1))) can afford accessible transport channels for effectively decreasing the mass transport resistances, enhancing the electrical conductivity, and increasing the density and reactivity of the exposed catalytic active sites. All these advantages will be responsible for the better electrocatalytic performances of these MFe2O4 NFs compared with their structural isomers (i.e. the MFe2O4 NPs) for the oxygen evolution reaction (OER) and H2O2 reduction in alkaline solution. Meanwhile, both the OER and H2O2 reduction catalytic activities for these MFe2O4 NFs obey the order of CoFe2O4 NFs > CuFe2O4 NFs > NiFe2O4 NFs > MnFe2O4 NFs > Fe2O3 NFs. The CoFe2O4 NFs represent a new class of highly efficient non-noble-metal catalysts for both OER and H2O2 reduction/detection in alkaline media.

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The Cu-based MOF loaded on macroporous carbon (MPC) creates novel Cu-MOF-MPC hybrids for the first time. The obtained Cu-MOF-MPC composites are used as electrocatalysts for the oxidation of NADH and reduction of H2O2 in neutral solution.

Facile synthesis of tiny CoP nanocrystal decorated porous carbon matrices as highly active non-noble-metal electrocatalysts for the HER in acidic solution.

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Ordered mesoporous boron-doped carbons (BOMCs) were prepared by co-impregnation and carbonization of sucrose and 4-hydroxyphenylboronic acid into SBA-15 silica template. Nitrogen sorption, small angle X-ray diffraction (XRD), and transmission electron microscopy (TEM) reveals that BOMCs possess highly ordered mesoporous structure, uniform pore size distribution, and high surface area. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that B atoms can be successfully doped into the framework of OMCs. Due to the desirable characteristics of BOMCs, BOMCs are highly active, cheap, and selective metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution. Although B content is a key factor in determining ORR activity, the ORR activity of BOMCs is also dependent on the surface area. The high surface area of BOMCs facilitates the exposure of the active sites for ORR. BOMCs may be further exploited as potentially efficient and inexpensive metal-free ORR catalysts with good long-term stability in alkaline solution.