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Nonmetallic doping and in situ growth techniques for designing electrode materials with excellent electrocatalytic activity are effective strategies to enhance the electrochemical performance. Bifunctional electrode materials for supercapacitors (SCs) and the hydrogen evolution reaction (HER) have attracted great interest due to their potential applications in green energy storage and conversion. Herein, the bimetallic MnCo LDH is anchored on a hollow sulfur (S)-doped MnCo-MOF-74 surface, forming a poplar flower-like 3D composite which is used for SCs and the HER in alkaline media. The fabricated S-MnCo-MOF-74@MnCo LDH/NF electrode exhibits a favorable specific capacitance of 1875.4 F g−1 at 1 A g−1 and steady long-term cycling performance. Moreover, the assembled HSC using S-MnCo-MOF-7@MnCo LDH/NF as the cathode material and active carbon (AC) as the anode material shows 546.4 F g−1 capacitance (1 A g−1) with a maximum energy density of 58 W h kg−1 at 14 000 W kg−1 power density. As an electrocatalyst, S-MnCo-MOF-7@MnCo LDH/NF exhibits excellent HER properties with a small Tafel slope of 128.9 mV dec−1 a low overpotential of 197 mV at 10 mA cm−2 and durable performance for 10 hours in alkaline media. The present work provides insights into understanding and designing active electrode materials for stable hydrogen evolution and high-performing supercapacitors in an alkaline environment. [ABSTRACT FROM AUTHOR]

The first polyoxometalate (POM)-encapsulated twenty-four-nucleus organophosphorus-copper nanocage cluster organic framework has been constructed. Here, the phosphomolybdate POMs were incorporated into an octahedral nanocage cluster organic framework, and the resulting material exhibited highly efficient bifunctional electrochemical performance. The crystalline material showed a high specific capacitance of 366.3 F g−1 at a current density of 3 A g−1. [ABSTRACT FROM AUTHOR]

A simple continuous hydrothermal method was used to synthesize a NiFe2O4@Ni–Mn LDH/NF composite. The layered structure provides a large void to transfer the electron effectively, and the composite materials exhibit remarkable electrochemical performance including excellent specific capacitance (1265 F g−1 at 1 A g−1) and remarkable cycling stability (the specific capacitance remains at 80.9% after 5000 cycles). In addition, the asymmetric supercapacitor exhibits a high energy density of 96.2 W h kg−1 at a power density of 700 W kg−1, and there is an extraordinarily good cycling stability with a capacity retention rate of 92.5% after 4000 cycles. The outcomes indicate that the NiFe2O4@Ni–Mn LDH/NF composite electrode has potential application as a high-performance supercapacitor. [ABSTRACT FROM AUTHOR]

A new CuO–Cu2O/GO nanocomposite was prepared by using Cu(OAc)2 and graphene oxide (GO) as the main raw materials under hydrothermal conditions in the presence of cetyltrimethyl ammonium bromide (CTAB). The structures of CuO–Cu2O/GO were characterized by FT-IR spectroscopy, XRD, XPS, TEM and HR-TEM. The results showed that the nanoparticles of CuO and Cu2O as heterostructures have been simultaneously grown in situ on GO sheets with 10–15 nm particle size. The photocatalytic properties of the nanocomposite were evaluated for the photocatalytic degradation of organic dyes and tetracycline pollutants. The designed nanocomposite showed excellent dual function catalytic ability for the rapid catalytic oxidation of tetracycline (TC) and methyl orange (MO). The degradation ratios of TC and MO reached 90% and 95% after 120 min (under visible light), respectively. The high catalytic activity is mainly due to the excellent photogenerated electron–hole transfer properties of the CuO–Cu2O/GO nanocomposite. [ABSTRACT FROM AUTHOR]

A novel polyoxometalate-based metal–organic framework templated by twin-Dawson clusters, [{Cu3(μ3-O)}2(trz)6Cu2(H2O)13][H1.73P2As1.73W16.27O62]·8.25H2O (1) (trz = 1,2,4-triazole), has been synthesized under hydrothermal conditions. In 1, there are two crystal distinct motifs: a 3D metal–organic nanotube framework and seven-connected Dawson clusters. It is worth mentioning that the 3D framework possesses nanotube-like channels. The twin-H1.73P2As1.73W16.27O62 clusters (abbreviated as P2(As/W)18 clusters) as templates occupy channels of the nanotube framework. To the best of our knowledge, this represents the first metal–organic nanotube framework templated by twin-Dawson clusters. The electrochemical experiments indicate that the 1-based glassy carbon electrode (1-GCE) possesses high catalytic efficiency and high stability toward reduction of inorganic bromate molecules and oxidation of the biological molecule ascorbic acid. The electrocatalytic efficiency towards the reduction of bromate in 1 M H2SO4 solution and oxidation of AA in N2 purged solution is ca. 848.4% and 896.8% (catalytic substrate: 0.5 mM), respectively. The current signal after 100 cycles exhibits almost no loss for 1-GCE. [ABSTRACT FROM AUTHOR]

A new polyoxovanadate-based metal–organic framework, [Cu(Pz)](V4O10) (1) (Pz = Pyrazine) has been synthesized under hydrothermal conditions. Single crystal X-ray diffraction analysis reveals that compound 1 displays a 3D framework with a rare reduced V4O102− layer. The electrochemical study shows that 1 exhibits bifunctional electrocatalytic activities toward reduction of iodate and oxidation of ascorbic acid. Surface photovoltage spectroscopy (SPS) and electric field induced surface photovoltage spectroscopy (EFISPS) measurements reveal that 1 has the behavior of an n-type semiconductor. In addition, 1 shows excellent photocatalytic activity for the decomposition of Rhodamine-B dye under visible light. [ABSTRACT FROM AUTHOR]

Two unprecedented polyoxometalate-encapsulated twenty-nuclear silver-tetrazole nanocage frameworks have been synthesized, which exhibit high activity in hydrogen evolution reaction. HUST-100 shows an onset overpotential of 148 mV and a Tafel slope of 82 mV dec−1, and the catalytic current density approaches 10 mA cm−2 at an overpotential of 234 mV. [ABSTRACT FROM AUTHOR]

A new coordination polymer, (H2bpe)(Hbpe)2{[Cu(pzta)(H2O)][P2W18O62]}·5H2O (1) (pztaH = 5-(2-pyrazinyl) tetrazolate, bpe = bis(4-pyridyl)ethylene), was synthesized by the hydrothermal method. The structure was determined by single crystal X-ray diffraction analyses and further characterized by the SEM, EDS, BVS, FTIR, and PXRD techniques. In 1, the [P2W18O62]6− (P2W18) clusters as bidentate connectors link [Cu(pzta)(H2O)]24+ dinuclear copper(ii) complexes to form inorganic–organic chains. These chains and the [H2bpe]2+ counter-cations are fused together via hydrogen bonding to form a 3D supramolecular architecture. While 1 was employed as the electrode in a supercapacitor, the cycling stability (90.7% capacitance retention after 1000 circles) and specific capacitance (168 F g−1 at a current density of 5 A g−1) of the 1-based electrode are better than those of the parent α-K6P2W18O62-based electrode, demonstrating more outstanding electrochemical performances of 1. Besides, the 1-based electrode showed excellent electrocatalytic activities towards the reduction of H2O2 and KIO3. [ABSTRACT FROM AUTHOR]

Three new compounds have been synthesized at different pHs under identical hydrothermal conditions, namely, (H2bimb)[Cu(bimb)3(H2O)2(H2P2W18O62)]·4H2O (1), (H2bimb)3[Cu2(bimb)5(H2O)4(HP2W18O62)2]·9H2O (2), and (H2bimb)5[Cu(bimb)2(H2O)2(P2W18O62)2]·8H2O (3) (bimb = 4-bis(imidazol-1-yl)benzene). Their structures were determined using single crystal X-ray diffraction analyses and characterized using routine methods. When the pH was adjusted to 2.0–2.5, compound 1 was obtained, which is a monomer. Compounds 2 and 3 were obtained at pH values of 2.5–3.2 and 3.2–4.0, which are two kinds of distinct dimers (I and II), respectively. The pH of the reaction plays a key role in the assembly of POM-based hybrid aggregates. Electrochemical experiments indicate that a 1-based carbon paste electrode (1-CPE) exhibits high catalytic efficiency and high stability towards reduction of NO2−. Namely, the electrocatalytic efficiency towards the reduction of NO2− is ca. 235% in 1 M H2SO4 containing 50 mM NO2−, and the current signal after 100 cycles exhibits almost no loss for the 1-CPE. [ABSTRACT FROM AUTHOR]

To explore the influence of the charge/polarity of Keggin polyanions and coordination modes of transition metal cations on the construction of polyoxometalate (POM)-based hybrid compounds, we design two synthetic routes and obtain six new POM-based inorganic–organic hybrid compounds, namely, [Co5(H2O)6(bimb)8(PWVI10WV2O40)2]·14H2O (1), [Co2(bimb)2(GeW12O40)][bimb]·2H2O (2), [Co2(bimb)2(BW12O40)][Hbimb]·2H2O (3), [Co2(bimb)2(H2W12O40)][H2bimb]·2H2O (4), [Cu(bimb)(BW12O40)][H2bimb]2·2H2O (5) and [Ag2(bimb)2(BW12O40)][H3bimb]·2H2O (6) (bimb = 1,4-bis(1-imidazolyl)benzene). All compounds were characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction. Compound 1 represents the first POM-based three-dimensional (3D) self-penetrating structure composed of a unique metal–organic polycatenated framework and tridentate Keggin clusters. Compounds 2, 3, 4 and 6 are isostructural, which show POMOF structures consisting of Keggin cluster guests and a metal–organic nanotube host. The structure of compound 5 is a simple 2D grid layer. The isolation of the title compounds is very informative for systematically understanding the effect of the charge/polarity of POMs and coordination modes of transition metal cations on the structures of POM-based hybrids. The effect of the charge/polarity of POMs and coordination modes of transition metal cations is discussed in this work. Additionally, the luminescence and electrochemical properties of 1–6 have been investigated in detail. [ABSTRACT FROM AUTHOR]

To explore the influence of the charge/polarity of Keggin polyanions and coordination modes of transition metal cations on the construction of polyoxometalate (POM)-based hybrid compounds, we design two synthetic routes and obtain six new POM-based inorganic–organic hybrid compounds, namely, [Co5(H2O)6(bimb)8(PWVI10WV2O40)2]·14H2O (1), [Co2(bimb)2(GeW12O40)][bimb]·2H2O (2), [Co2(bimb)2(BW12O40)][Hbimb]·2H2O (3), [Co2(bimb)2(H2W12O40)][H2bimb]·2H2O (4), [Cu(bimb)(BW12O40)][H2bimb]2·2H2O (5) and [Ag2(bimb)2(BW12O40)][H3bimb]·2H2O (6) (bimb = 1,4-bis(1-imidazolyl)benzene). All compounds were characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction. Compound 1 represents the first POM-based three-dimensional (3D) self-penetrating structure composed of a unique metal–organic polycatenated framework and tridentate Keggin clusters. Compounds 2, 3, 4 and 6 are isostructural, which show POMOF structures consisting of Keggin cluster guests and a metal–organic nanotube host. The structure of compound 5 is a simple 2D grid layer. The isolation of the title compounds is very informative for systematically understanding the effect of the charge/polarity of POMs and coordination modes of transition metal cations on the structures of POM-based hybrids. The effect of the charge/polarity of POMs and coordination modes of transition metal cations is discussed in this work. Additionally, the luminescence and electrochemical properties of 1–6 have been investigated in detail. [ABSTRACT FROM AUTHOR]

By introducing different polyoxomolybdates into a Cu–bimb system (bimb = 1,4-bis(imidazol-1-yl) benzene), three new polyoxomolybdate-based inorganic–organic hybrids with distinct architectures, [CuII(bimb)1.5(H2O)(β-Mo8O26)0.5] (1), (Hbimb)2[CuI(bimb)(PMo12O40)]·4H2O (2) and [CuI4(bimb)4(SiMo12O40)]·2H2O (3), have been synthesized under identical hydrothermal conditions and characterized by routine methods. Compound 1 displays an interesting 2-fold interpenetrated structure consisting of two identical layers. When the polyoxomolybdate clusters were changed from β-[Mo8O26]4− to [PMo12O40]3−, and [SiMo12O40]4−, compounds 2 and 3, respectively, were obtained. Compound 2 shows a highly opened three-dimensional framework, while compound 3 exhibits a three-dimensional interdigitated architecture. The different structural features of compounds 1–3 suggest that the influences of different polyoxometalate clusters on structure must play a key role in the process of assembling. Additionally, both the luminescent and electrochemical properties for 1–3 have been investigated. [ABSTRACT FROM AUTHOR]

The first (7,8)-connected polyoxometalate-based metal–organic framework (POM–MOF) has been constructed from seven- and eight-connected twin Wells–Dawson clusters, and possesses the highest connection number of polyoxometalates to any mixed-connected POM–MOF to date and a unique structural motif that contains both organic–inorganic and all-inorganic networks. [ABSTRACT FROM AUTHOR]

A compound, [CuI5(pz)6(H2O)4][PWVI10WV2O40] (1) (pz = pyrazine), with a novel Cu12(pz)12 loop-based coordination polymer templated by double-Keggin anions, has been hydrothermally synthesized, and its photocatalytic activity has also been investigated. The results indicate that the title compound exhibits good photocatalytic activity towards degradation of rhodamine B dye and could be a potential photocatalyst for decomposition of rhodamine B dye. [ABSTRACT FROM AUTHOR]

By choosing asymmetric L ligands (L = 1-(imidazol-1-yl)-4-(1,2,4-triazol-1-ylmethyl)benzene), Cu2+/Co2+ cations and Keggin clusters as starting materials, two new POM-based zipper-like compounds, {Cu(L)4[HPMo12O40]}·4H2O (1) and {[Co(L)4][HPMo8VV4O40(VIVO)2]} (2), have been hydrothermally synthesized and characterized by elemental analyses, single-crystal X-ray diffraction, XPS, powder X-ray diffraction, IR spectroscopy, and TG analyses. A structural feature of 1 and 2 is that there exists a 1D + 1D → 3D interdigitated architecture achieved using molecular zippers, in which overhanging mono-coordinated L arms act as teeth. Compound 2 shows bifunctional electrocatalytic activities toward not only reduction of normal iodated inorganic molecules (IO3−) ascribed to Mo-centers, but also oxidation of biological molecules such as ascorbic acid (AA) ascribed to V-centers. [ABSTRACT FROM AUTHOR]

A novel compound, Na2[Ce4(H2O)22(dpdo)5](Mn2HP2W15O56)2·8H2O (1) (dpdo = 4,4′-bipyridine-N,N′-dioxide) with 3d–4f heterometallic 3D POMOF that can be described as a self-penetrating (4,4,6)-connected net topology, has been isolated via a stepwise method, and its magnetic and electrocatalytic properties have been investigated. [ABSTRACT FROM AUTHOR]

Nonmetallic doping and in situ growth techniques for designing electrode materials with excellent electrocatalytic activity are effective strategies to enhance the electrochemical performance. Bifunctional electrode materials for supercapacitors (SCs) and the hydrogen evolution reaction (HER) have attracted great interest due to their potential applications in green energy storage and conversion. Herein, the bimetallic MnCo LDH is anchored on a hollow sulfur (S)-doped MnCo-MOF-74 surface, forming a poplar flower-like 3D composite which is used for SCs and the HER in alkaline media. The fabricated S-MnCo-MOF-74@MnCo LDH/NF electrode exhibits a favorable specific capacitance of 1875.4 F g -1 at 1 A g -1 and steady long-term cycling performance. Moreover, the assembled HSC using S-MnCo-MOF-7@MnCo LDH/NF as the cathode material and active carbon (AC) as the anode material shows 546.4 F g -1 capacitance (1 A g -1 ) with a maximum energy density of 58 W h kg -1 at 14 000 W kg -1 power density. As an electrocatalyst, S-MnCo-MOF-7@MnCo LDH/NF exhibits excellent HER properties with a small Tafel slope of 128.9 mV dec -1 a low overpotential of 197 mV at 10 mA cm -2 and durable performance for 10 hours in alkaline media. The present work provides insights into understanding and designing active electrode materials for stable hydrogen evolution and high-performing supercapacitors in an alkaline environment.

The first polyoxometalate (POM)-encapsulated twenty-four-nucleus organophosphorus-copper nanocage cluster organic framework has been constructed. Here, the phosphomolybdate POMs were incorporated into an octahedral nanocage cluster organic framework, and the resulting material exhibited highly efficient bifunctional electrochemical performance. The crystalline material showed a high specific capacitance of 366.3 F g-1 at a current density of 3 A g-1.

A simple continuous hydrothermal method was used to synthesize a NiFe 2 O 4 @Ni-Mn LDH/NF composite. The layered structure provides a large void to transfer the electron effectively, and the composite materials exhibit remarkable electrochemical performance including excellent specific capacitance (1265 F g -1 at 1 A g -1 ) and remarkable cycling stability (the specific capacitance remains at 80.9% after 5000 cycles). In addition, the asymmetric supercapacitor exhibits a high energy density of 96.2 W h kg -1 at a power density of 700 W kg -1 , and there is an extraordinarily good cycling stability with a capacity retention rate of 92.5% after 4000 cycles. The outcomes indicate that the NiFe 2 O 4 @Ni-Mn LDH/NF composite electrode has potential application as a high-performance supercapacitor.

A new coordination polymer, (H 2 bpe)(Hbpe) 2 {[Cu(pzta)(H 2 O)][P 2 W 18 O 62 ]}·5H 2 O (1) (pztaH = 5-(2-pyrazinyl) tetrazolate, bpe = bis(4-pyridyl)ethylene), was synthesized by the hydrothermal method. The structure was determined by single crystal X-ray diffraction analyses and further characterized by the SEM, EDS, BVS, FTIR, and PXRD techniques. In 1, the [P 2 W 18 O 62 ] 6- (P 2 W 18 ) clusters as bidentate connectors link [Cu(pzta)(H 2 O)] 2 4+ dinuclear copper(ii) complexes to form inorganic-organic chains. These chains and the [H 2 bpe] 2+ counter-cations are fused together via hydrogen bonding to form a 3D supramolecular architecture. While 1 was employed as the electrode in a supercapacitor, the cycling stability (90.7% capacitance retention after 1000 circles) and specific capacitance (168 F g -1 at a current density of 5 A g -1 ) of the 1-based electrode are better than those of the parent α-K 6 P 2 W 18 O 62 -based electrode, demonstrating more outstanding electrochemical performances of 1. Besides, the 1-based electrode showed excellent electrocatalytic activities towards the reduction of H 2 O 2 and KIO 3 .

By choosing V-shaped ligands, Cu2+ cations and isopolymolybdates as starting materials, a novel double helical compound [Cu(H2O)(bimb)]2[β-Mo8O26] (1) (bimb = 1,3-bis(1-imidazoly)benzene) was hydrothermally synthesized and characterized by elemental analyses, single-crystal X-ray diffraction, powder X-ray diffraction and IR spectroscopy. A structural feature is that compound 1 represents the first example of a helical compound based on polyoxometalates, which possesses an unprecedented helical disposition, namely the coexistence of both interconnected and interweaved double helices in one structure. The photocatalytic properties of compound 1 were also investigated in detail and the result of photocatalytic experiments shows that compound 1 can be used as a stable photocatalyst toward the decomposition of the organic pollutant methylene blue.

A novel compound, Na2[Ce4(H2O)22(dpdo)5](Mn2HP2W15O56)2·8H2O (1) (dpdo = 4,4'-bipyridine-N,N'-dioxide) with 3d-4f heterometallic 3D POMOF that can be described as a self-penetrating (4,4,6)-connected net topology, has been isolated via a stepwise method, and its magnetic and electrocatalytic properties have been investigated.