Tailoring the Hydrophobic Interface of Core-Shell HKUST-1@Cu2O Nanocomposites for Efficiently Selective CO2 Electroreduction.

The electrochemical reduction of carbon dioxide (CO2) to ethylene creates a carbon-neutral approach to converting carbon dioxide into intermittent renewable electricity. Exploring efficient electrocatalysts with potentially high ethylene selectivity is extremely desirable, but still challenging. In this report, a laboratory-designed catalyst HKUST-1@Cu2O/PTFE-1 is prepared, in which the high specific surface area of the composites with improved CO2 adsorption and the abundance of active sites contribute to the increased electrocatalytic activity. Furthermore, the hydrophobic interface constructed by the hydrophobic material polytetrafluoroethylene (PTFE) effectively inhibits the occurrence of hydrogen evolution reactions, providing a significant improvement in the efficiency of CO2 electroreduction. The distinctive structures result in the remarkable hydrocarbon fuels generation with high Faraday efficiency (FE) of 67.41%, particularly for ethylene with FE of 46.08% (-1.0 V vs RHE). The superior performance of the catalyst is verified by DFT calculation with lower Gibbs free energy of the intermediate interactions with improved proton migration and selectivity to emerge the polycarbon（C2+） product. In this work, a promising and effective strategy is presented to configure MOF-based materials with tailored hydrophobic interface, high adsorption selectivity and more exposed active sites for enhancing the efficiency of the electroreduction of CO2 to C2+ products with high added value.

Surface band bending caused by native oxides on solution-processed twinned InSb nanowires with p-type conductivity.

Indium antimonide nanowires (InSb NWs) are attractive building-block candidates for bottom-up construction of high-efficiency electronics and optoelectronics due to their narrow direct band gap, fast room temperature carrier mobilities and small exciton binding energy. However, InSb NWs synthesized by the vapor-liquid-solution (VLS) mechanism generally suffer from an increased carrier and phonon scattering rate, which is thought to be caused by randomly distributed crystal defects along the NW growth direction. In this study, by utilizing the recently developed low-temperature, solution-processed technique, these crystal defects were successfully suppressed by periodically distributed twin planes to form twinned InSb nanowires. Importantly, measurements of the electrical transport properties of field effect transistors (FETs) reveal that the InSb NWs exhibit a hole-dominated conductivity with room temperature mobilities of up to 50.71 cm2 V-1 s-1, which is distinctly contrary to the intrinsic n-type InSb NWs. This observation of n-p switching behavior is probably attributed to the surface band bending effect with regard to the Fermi energy level, which is caused by surface oxide trap states arising from the native-oxide layer at the surface of the InSb NWs. All these results illustrate that the as-prepared colloidal InSb NWs can potentially be used as p-type materials for integration with next-generation nanoscale electronics and optoelectronics via surface engineering.

Self-Sacrificing Template of the POMs-Based Composite for the High-Performance Organic-Inorganic Hybrid Cathode of Lithium-Ion Batteries.

The high theoretical capacity of vanadium oxides makes them promising cathode candidates for the rechargeable lithium-ion batteries (LIBs). Nevertheless, the relatively poor electrical conductivity and capacity retention hinder the practical application and have to be overcome urgently for the increasing demand for storage technologies. Herein, a new BRG system composed of bimetallic oxide/rhodamine B (RB)/reduced graphene oxide (RGO) was prepared through the facile self-sacrificing template of the precursor polyoxometalate (POM) composites POMs/RB/RGO (PRG). RB not only acts as a cationic mediator to facilitate the loading of POMs on graphene for conversion to oxides but also promotes the formation of uniform nanorods on the RGO. The prepared composite FeV3O8-RB/RGO-1 as the cathode exhibits superior cycling stability (specific capacity of 225 mA h g-1 at 100 mA g-1) and elastic rate capabilities for LIBs. What is more, the new PRG precursor provides versatile possibilities for the design of oxide composites from the self-sacrificing template of POMs-based composites with abundant architectural designs and compositions for the energy storage system.

Oriented electron transmission in polyoxometalate-metalloporphyrin organic framework for highly selective electroreduction of CO2.

The design of highly stable, selective and efficient electrocatalysts for CO2 reduction reaction is desirable while largely unmet. In this work, a series of precisely designed polyoxometalate-metalloporphyrin organic frameworks are developed. Noted that the integration of {ε-PMo8VMo4VIO40Zn4} cluster and metalloporphyrin endows these polyoxometalate-metalloporphyrin organic frameworks greatly advantages in terms of electron collecting and donating, electron migration and electrocatalytic active component in the CO2 reduction reaction. Thus-obtained catalysts finally present excellent performances and the mechanisms of catalysis processes are discussed and revealed by density functional theory calculations. Most importantly, Co-PMOF exhibits remarkable faradaic efficiency ( > 94%) over a wide potential range (-0.8 to -1.0 V). Its best faradaic efficiency can reach up to 99% (highest in reported metal-organic frameworks) and it exhibits a high turnover frequency of 1656 h-1 and excellent catalysis stability ( > 36 h).

Polyoxometalate-Based Metal-Organic Frameworks with Conductive Polypyrrole for Supercapacitors.

Metal-organic frameworks (MOFs) with high porosity could act as an ideal substitute for supercapacitors, but their poor electrical conductivities limit their electrochemical performances. In order to overcome this problem, conductive polypyrrole (PPy) has been introduced and a novel nanocomposite resulting from polyoxometalate (POM)-based MOFs (NENU-5) and PPy has been reported. It comprises the merits of POMs, MOFs, and PPy. Finally, the highly conductive PPy covering the surfaces of NENU-5 nanocrystallines can effectively improve the electron/ion transfer among NENU-5 nanocrystallines. The optimized NENU-5/PPy nanocomposite (the volume of Py is 0.15 mL) exhibits high specific capacitance (5147 mF·cm-2), larger than that of pristine NENU-5 (432 mF·cm-2). Furthermore, a symmetric supercapacitor device based on a NENU-5/PPy-0.15 nanocomposite possesses an excellent areal capacitance of 1879 mF·cm-2, which is far above other MOF-based supercapacitors.

Rational Design of MOF/COF Hybrid Materials for Photocatalytic H2 Evolution in the Presence of Sacrificial Electron Donors.

Crystalline and porous covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) materials have attracted enormous attention in the field of photocatalytic H2 evolution due to their long-range order structures, large surface areas, outstanding visible light absorbance, and tunable band gaps. In this work, we successfully integrated two-dimensional (2D) COF with stable MOF. By covalently anchoring NH2 -UiO-66 onto the surface of TpPa-1-COF, a new type of MOF/COF hybrid materials with high surface area, porous framework, and high crystallinity was synthesized. The resulting hierarchical porous hybrid materials show efficient photocatalytic H2 evolution under visible light irradiation. Especially, NH2 -UiO-66/TpPa-1-COF (4:6) exhibits the maximum photocatalytic H2 evolution rate of 23.41 mmol g-1 h-1 (with the TOF of 402.36 h-1 ), which is approximately 20 times higher than that of the parent TpPa-1-COF and the best performance photocatalyst for H2 evolution among various MOF- and COF-based photocatalysts.

Proton conductivity resulting from different triazole-based ligands in two new bifunctional decavanadates.

Triazole, similarly to imidazole, makes a prominent contribution to the proton conductivity of porous materials. To investigate the effects of triazole-based ligands in polyoxovanadates (POVs) on proton conduction, we designed and synthesized two decavanadate-based POVs, [Zn3(C2H4N4)6(H2O)6](V10O28)·14H2O (1) and [Zn3(C2H3N3)8(H2O)4](V10O28)·8H2O (2) constructed from the ligands 3-amino-1,2,4-triazole and 1H-1,2,4-triazole, respectively, via an aqueous solution evaporation method. Surprisingly, complex 1 obtained a superior proton conductivity of 1.24 × 10-2 S cm-1 under 60 °C and 98% RH, which is much higher than that of complex 2. Furthermore, due to the contribution of the conjugate properties of the ligands to the third-order nonlinear optical (NLO) properties, we also studied its two-photon responses and achieved satisfactory results.

A highly stable polyoxometalate-based metal-organic framework with an ABW zeolite-like structure.

A novel polyoxometalate-based metal-organic framework (POMOF) with an ABW network, NENU-601, was synthesized in situ. To the best of our knowledge, this is the first POMOF with a zeolite-like structure, which was designed by regulating the length and angle of mixed ligands and rationally choosing suitable Polyoxometalates (POMs) as nodes.

Polyoxomolybdate-Polypyrrole/Reduced Graphene Oxide Nanocomposite as High-Capacity Electrodes for Lithium Storage.

A nanocomposite polyoxomolybdate (PMo12)-polypyrrole (PPy)/reduced graphene oxide (RGO) is fabricated by using a simple one-pot hydrothermal method as an electrode material for lithium-ion batteries. This facile strategy skillfully ensures that individual polyoxometalate (POM) molecules are uniformly immobilized on the RGO surfaces because of the wrapping of polypyrrole (PPy), which avoids the desorption and dissolution of POMs during cycling. The unique architecture endows the PMo12-PPy/RGO with the lithium storage behavior of a hybrid battery-supercapacitor electrode: the nanocomposite with a lithium storage capacity delivers up to 1000 mAh g-1 at 100 mA g-1 after 50 cycles. Moreover, it still demonstrates an outstanding rate capability and a long cycle life (372.4 mAh g-1 at 2 A g-1 after 400 cycles). The reversible capacity of this nanocomposite has surpassed most pristine POMs and POMs-based electrode materials reported to date.