This review summarizes the use of metal-organic frameworks (MOFs) as a versatile supramolecular platform to develop heterogeneous catalysts for a variety of organic reactions, especially for liquid-phase reactions. Following a background introduction about catalytic relevance to various metal-organic materials, crystal engineering of MOFs, characterization and evaluation methods of MOF catalysis, we categorize catalytic MOFs based on the types of active sites, including coordinatively unsaturated metal sites (CUMs), metalloligands, functional organic sites (FOS), as well as metal nanoparticles (MNPs) embedded in the cavities. Throughout the review, we emphasize the incidental or deliberate formation of active sites, the stability, heterogeneity and shape/size selectivity for MOF catalysis. Finally, we briefly introduce their relevance into photo- and biomimetic catalysis, and compare MOFs with other typical porous solids such as zeolites and mesoporous silica with regard to their different attributes, and provide our view on future trends and developments in MOF-based catalysis.

Developing electrode materials with both high energy and power densities holds the key for satisfying the urgent demand of energy storage worldwide. Herein, we demonstrate the successful preparation of Co3V2O8 nanostructures that are constructed from self-assembly of ultrathin nanosheets via a simple hydrothermal method followed by annealing in air at 350 °C for 2 h. A "slipping-exfoliating-self reassembly" model based on the time-dependent experiments was proposed to elucidate the formation of the hierarchical nanosheets. When tested as lithium ion anodes, the as-synthesized multilayered nanoarchitectures exhibit outstanding reversible capacity (1114 mA h g(-1) retained after 100 cycles) and excellent rate performance (361 mA h g(-1) at a high current density of 10 A g(-1)) for lithium storage. Detailed investigations of the morphological and structural changes of Co3V2O8 upon cycling reveal an interesting kinetics toward lithium ion intercalations, where reversible conversion reactions between Co and CoO are found proceeding on the amorphous lithiated vanadium oxides matrixes. We believe that this observation is a valuable discovery for metal vandates-based lithium ion anodes. The superior electrochemical performances of the multilayered Co3V2O8 nanosheets can be attributed to the unique morphologies and particularly the surface-to-surface constructions that are generated during the lithium ion insertion processes.

Transparency has never been integrated into freestanding flexible graphene paper (FF-GP), although FF-GP has been discussed extensively, because a thin transparent graphene sheet will fracture easily when the template or substrate is removed using traditional methods. Here, transparent FF-GP (FFT-GP) was developed using NaCl as the template and was applied in transparent and stretchable supercapacitors. The capacitance was improved by nearly 1000-fold compared with that of the laminated or wrinkled chemical vapor deposition graphene-film-based supercapacitors.

No abstract

New layered SnS2 nanosheet arrays consisting of 1–5 atomic layers were synthesized directly on Sn foil as both the tin source and the metal current collector substrates by a simple biomolecule-assisted method. It is found that SnS2 nanosheets synthesized have excellent photoelectric applications, such as on lithium ion batteries, and photocatalytic, field emission, and photoconductive properties. Cyclic voltammetry and discharge and charge behaviors of the atomic SnS2 nanosheets were examined, and it shows that the average discharge capacity in 1050 mAh/g is much larger than the theoretical capacity at the 1C rate. The photocatalytic action driven by solar light is quite quick, and the degradation rate of RhB is 90%, only irradiated for 20 min when the content of SnS2 nanosheets is 0.4 g/L. The response of the SnS2 device to the incidence UV light is very fast and shows excellent photosensitivity and stability. In addition, field emission properties of SnS2 nanosheets were also researched, and we found that the turn-on field for SnS2 is 6.9 V/μm, which lowered ever reported values. The enhanced photoelectric properties are likely to originate in a graphene-like structure. Thus, graphene-like SnS2 materials are promising candidates in the photoelectric field.

Although nanomaterials investigations have been carried over the recent decades, researchers still face a fundamental challenge: how to control the phase, size and shape of nanocrystals in the synthesis of nanomaterials, i.e., how to achieve the transformation from nanocrytsal synthesis to functional nanostructure fabrication. For this issue, we, in this review, introduce recent developments in laser ablation in liquid (LAL) for the synthesis and fabrication of novel nanostructures with metastable phases and shapes. Laser ablation of solid targets in liquid has actually opened a door toward to synthesize nanocrystals and fabricate nanostructures due to these advantages as follows: (i) LAL is a chemically "simple and clean" synthesis due to the process with reduced byproduct formation, simpler starting materials, no need for catalyst, etc. (ii) Under ambient conditions, not extreme temperature and pressure, a variety of metastable phases that may not usually be attainable, can be generated by mild preparation methods. (iii) New phase formation involves in both liquid and solid upon LAL, which allows researchers to choose and combine interesting solid target and liquid to synthesize nanocrystals and fabricate nanostructures of new compounds for purpose of fundamental research and potential applications. (iv) The phase, size and shape of the synthesized nanocrystals can be readily controlled by tuning laser parameters and applying assistances such as inorganic salts or electrical field upon LAL. For example, we have synthesized the micro- and nanocubes of carbon with C(8)-like structures by the inorganic salts assisted LAL, and the micro- and nanocubes and spindles of GeO(2) by the electrical field assisted LAL. Additionally, we have developed a new technique to fabricate functional nanopatterns on the basis of the pulsed-laser deposition in liquid. Accordingly, LAL could greatly extend its application in fabrication of functional nanostructures in the future.

A new kinetic model is suggested to describe the self-limiting oxidation of Si nanowires by only considering the diffusion step with the influence of stress due to the two-dimension nonuniform deformation of the oxide but not including any rate-limiting step for interfacial reaction. It is assumed the stress results in the change of distribution of diffusion activation energy in the high density region which rises monotonically along with the oxidation, and may be the main physical origin of the self-limiting oxidation behavior of SiNWs. Moreover, the present kinetic model can excellently describe the experimental results for the wide initial diameter over the range of self-limiting oxidation temperature.

Highly efficient energy storage systems are in great demand for power source applications ranging from wearable electronics to hybrid electric vehicles. Graphene-based hybrid structure capacitors are ideal candidates for manufacturing these systems. Herein, we present the design and fabrication of heterostructured composites made of vertically aligned graphene nanosheets (VAGN) and MnO nanoparticles. Electrodes with various MnO mass contents were obtained by depositing nanosized MnO particles onto VAGN under different hydrothermal conditions. The VAGN served as an excellent backbone and electron collector, enhancing the specific capacitance of the VAGN/MnO electrode (37 wt% MnO) to 790 F g À1 at a scan rate of 2 mV s À1 . The electrodes also showed high specific capacitance (381 F g À1 ) with high active material loading content (80 wt% MnO), and outstanding cycling stability (80% retention after 4000 cycles at 10 A g À1 ). These excellent electrochemical performances result from the particular three-dimensional structure of VAGN, which offers convenient access for electrolyte cations participating in the redox reaction of MnO. These composites show enormous potential for use in energy management applications.