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Copper-oxo clusters have been of great interest due to their fascinating structures and potential applications. However, it was difficult to construct copper clusters using conjugated macromolecules by a conventional solvent method due to their insolubility. Herein, a hydroxo-bridged [Cu20] cluster was self-assembled through the employment of solvothermal techniques by using the conjugated macromolecule anthracene-9-carboxylic acid and copper bromide or cuprous bromide. The bromine anion as a template has been found to play a crucial role in the synthesis of the [Cu20] cluster compared to other anion-based copper salts, which form the paddlewheel [Cu2] cluster. The catalytic tests showed that the [Cu20] cluster exhibited an excellent conversion efficiency in the cycloaddition reaction of CO2 with epichlorohydrin. The turnover number (TON) was about 58 823, while the turnover frequency (TOF) was approximately 19 607 h−1. As far as we know, these values in this work for metal–organic catalysts were the highest among the previously reported catalytic data on the cycloaddition of CO2 to epoxide under similar conditions. The cycling test showed that the catalytic activity of the [Cu20] cluster in the cycloaddition of CO2 to epoxide was retained for five repeated cycles, indicating that the catalytic reaction was actually heterogeneous. The high catalytic efficiency and stability enable the use of raw power station flue gas, which reveals the broad prospect of this copper-oxo cluster in the industrial application of CO2 fixation. [ABSTRACT FROM AUTHOR]

The design and construction of wide-bandgap semiconductor nanostructures is a promising way to achieve photocatalytic overall water-splitting, because their redox potentials easily simultaneously satisfy the thermodynamic requirements of water reduction and oxidation. However, the narrow light-harvesting range and the fast charge recombination of wide-bandgap semiconductors tremendously limit their photocatalytic activities. Herein, we developed a novel wide-bandgap semiconductor photocatalyst of CaNb2O6 nanofibers (NFs) fabricated by an electrospinning technique, followed by calcination. Upon UV-visible light irradiation, the as-electrospun CaNb2O6 NFs could split water into H2 and O2 without adding any cocatalyst and sacrificial agent. The H2-production rate of CaNb2O6 NFs was ∼7.7 times higher than that of CaNb2O6 nanoparticles (NPs). It is because the CaNb2O6 NFs with the NP-packed 1D nanostructure possess abundant homogeneous interfaces to facilitate inter-particle continuous charge migration, thereby prolonging the lifetimes of photoinduced electrons and holes toward both water reduction and oxidation. Notably, the introduction of Au NPs into the CaNb2O6 NFs could extend light absorption from the UV to the visible light range. The optimal sample of 1.0 at% Au NP-decorated CaNb2O6 NFs exhibited ∼13.1-fold enhancement of photocatalytic activity for overall water splitting as compared to CaNb2O6 NFs. This remarkable enhancement is attributed to an interesting plasmonic sensitization process, during which the visible-light-excited hot electrons in plasmonic Au NPs are able to transfer to the interband-excited CaNb2O6 across their hetero-interface for enhancing the photocatalytic water reduction. Meanwhile, the hot holes left in the Au NPs possess a longer lifetime for fulfilling the photocatalytic water oxidation. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF) materials have been extensively incorporated with inorganic semiconductor photocatalysts to improve their photocatalytic activity through an efficient charge transfer process across their heterointerface. In this work, octahedral UiO-66-NH2 MOFs with edge-lengths of 110–330 nm are uniformly decorated on the surface of TiO2 electrospun nanofibers by a traditional solvothermal method combined with activation pretreatment. Before the solvothermal growth of UiO-66-NH2, the TiO2 electrospun nanofibers were activated in NaOH solution to etch the TiO2 surface for allowing the exposure of lattice oxygen. The exposed lattice oxygen on the TiO2 surface could interact with the MOF precursor of Zr4+ ions, thus enabling octahedral UiO-66-NH2 to grow uniformly on the surface of TiO2 nanofibers with an intimate Ti–O–Zr hetero-interface. Such an intimate hetero-interface provides an effective channel for boosting the electron transfer between UiO-66-NH2 and TiO2 in their heterostructure. Thus, the UiO-66-NH2/TiO2(anatase) heterostructures exhibited enhanced photocatalytic activity for H2 production as compared to either TiO2(anatase) nanofibers or UiO-66-NH2 nanooctahedra in the presence of Rhodamine B (RhB) as a sensitizer under visible light irradiation. In particular, the decoration of UiO-66-NH2 nanooctahedra on anatase/rutile mixed TiO2 nanofibers could induce further enhancement of the photocatalytic H2 production. The enhanced photocatalytic activity is attributed to the multi-step continuous interfacial transfer of photoinduced electrons with the way of RhB → UiO-66-NH2 → TiO2(anatase) → TiO2(rutile). [ABSTRACT FROM AUTHOR]

Porous crystalline materials, such as porous organic cages (POCs) and covalent organic frameworks (COFs), are important for a wide range of applications such as gas storage/separation, sensing and catalysis. A conventional synthetic approach for imine-based POCs and COFs usually involves the use of organic solvents/acid catalysts (such as AcOH or TFA). However, synthesizing and growing POC crystals and COF crystallites with enhanced crystallinity is not an easy-to-perform process, in which many reaction parameters need to be screened. To overcome these problems, we have proposed herein a facile and green synthetic strategy by adopting H2O/organic solvents/MOH (M = Na, K, and Cs) as reaction media to produce a series of phenol-based POCs and COFs. X-ray crystallography and molecular simulations have been used to confirm their structures in addition to NMR, mass and FT-IR spectra, and gas sorption experiments reveal their porosity and sorption properties. This new approach provides not only an efficient and alternative route to synthesize highly crystalline POCs and even COFs, but also insight into the crystallization process of these two kinds of porous materials, especially in the hydrous media. [ABSTRACT FROM AUTHOR]

Herein, an interesting electron-donating strategy is proposed to guide the construction of novel CdS-based MOFs for co-catalyst-free photocatalytic H2 evolution in the presence of triethanolamine as the hole-scavenger. The optimally designed CdS-based MOF exhibits an exceptional H2-evolution rate of 26.1 mmol g−1 h−1 which is almost the highest rate among the reported co-catalyst-free MOF systems. [ABSTRACT FROM AUTHOR]

One-dimensional SnO2/TiO2 heterostructures were successfully synthesized through the hydrothermal assembly of the single-crystalline SnO2 nanocubes onto the TiO2 electrospun nanofibers. The as-synthesized heterostructures with controllable coverage density of SnO2 nanocubes were then coated onto the ceramic-based interdigital electrodes to produce the humidity nanosensors for the investigation of their humidity sensing characteristics. The results showed that the optimal nanosensor with ∼20 at% SnO2-based heterostructure exhibited good humidity sensitivity, fast response–recovery behavior, low humidity hysteresis, and good reproducibility. In particular, the response and recovery times of this optimal nanosensor could reach ∼2.4 s and ∼30.2 s, respectively, which were considerably shorter than the corresponding values of TiO2 nanofiber-based humidity nanosensors. The improved sensitivity characteristics for the SnO2/TiO2 heterostructures can be attributed to the interfacial electron transfer between SnO2 nanocubes and TiO2 nanofibers, which leads to an appropriate height of the potential barrier on the surface of the heterostructures for water adsorption and desorption. Our proposed humidity sensing mechanism would provide opportunities to guide the design and fabrication of other high-performance humidity sensors based on semiconductor heterostructures. [ABSTRACT FROM AUTHOR]

Core/shell nanofibers of TiO2@carbon embedded by Ag nanoparticles (TiO2@C/Ag NFs) were fabricated by combining the electrospinning technique, the hydrothermal method and an in situreduction approach. The results showed that a uniform graphite carbon layer of approximately 8 nm in thickness was formed around the electrospun TiO2nanofiber and small Ag nanoparticles (Ag NPs) were dispersed well inside the carbon layer. And, the TiO2@C/Ag NFs had remarkable light absorption in the visible region. The photocatalytic studies revealed that the TiO2@C/Ag NFs exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) and Methyl Orange (MO) compared with the pure TiO2nanofibers, TiO2@carbon core/shell nanofibers and TiO2/Ag nanofibers under visible light irradiation, which might be attributed to the good light absorption capability and high separation efficiency of photogenerated electron–hole pairs based on the photosynergistic effect among the three components of TiO2, carbon and Ag. And, the TiO2@C/Ag NFs could be easily recycled due to their one-dimensional nanostructural property. [ABSTRACT FROM AUTHOR]

In this paper, a facile two-step synthesis route combining an electrospinning method and hydrothermal technique has been accepted as a straightforward protocol for the exploitation of Bi4Ti3O12/TiO2heterostructures which are composed of Bi4Ti3O12nanosheets on the surface of TiO2submicron fibers. The thickness of the as-grown nanosheets was about 20 nm and the size of the nanosheets increase with the increase of precursor concentration. Photocatalytic tests display that the Bi4Ti3O12/TiO2heterostructures possess a much higher degradation rate of rhodamine B (RB) than the unmodified TiO2submicron fibers under visible light. The enhanced photocatalytic activity can be attributed to the extended absorption in the visible light region resulting from the Bi4Ti3O12nanosheets, and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Bi4Ti3O12/TiO2junction interface. [ABSTRACT FROM AUTHOR]

The tubular nanocomposite with well-dispersed distribution of small gold nanoparticles (AuNPs) assembled on the inside and outside surfaces of silica nanotubes (SNTs) was fabricated by combining the single capillary electrospinning technique and an in situreduction approach. The AuNPs/SNTs nanocomposite exhibited a good catalytic activity for reduction of 4-nitrophenol (4-NP). [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF) materials have been extensively incorporated with inorganic semiconductor photocatalysts to improve their photocatalytic activity through an efficient charge transfer process across their heterointerface. In this work, octahedral UiO-66-NH2 MOFs with edge-lengths of 110-330 nm are uniformly decorated on the surface of TiO2 electrospun nanofibers by a traditional solvothermal method combined with activation pretreatment. Before the solvothermal growth of UiO-66-NH2, the TiO2 electrospun nanofibers were activated in NaOH solution to etch the TiO2 surface for allowing the exposure of lattice oxygen. The exposed lattice oxygen on the TiO2 surface could interact with the MOF precursor of Zr4+ ions, thus enabling octahedral UiO-66-NH2 to grow uniformly on the surface of TiO2 nanofibers with an intimate Ti-O-Zr hetero-interface. Such an intimate hetero-interface provides an effective channel for boosting the electron transfer between UiO-66-NH2 and TiO2 in their heterostructure. Thus, the UiO-66-NH2/TiO2(anatase) heterostructures exhibited enhanced photocatalytic activity for H2 production as compared to either TiO2(anatase) nanofibers or UiO-66-NH2 nanooctahedra in the presence of Rhodamine B (RhB) as a sensitizer under visible light irradiation. In particular, the decoration of UiO-66-NH2 nanooctahedra on anatase/rutile mixed TiO2 nanofibers could induce further enhancement of the photocatalytic H2 production. The enhanced photocatalytic activity is attributed to the multi-step continuous interfacial transfer of photoinduced electrons with the way of RhB → UiO-66-NH2 → TiO2(anatase) → TiO2(rutile).