Wei-Guo Song

Construction of Covalent Organic Framework for Catalysis: Pd/COF-LZU1 in Suzuki-Miyaura Coupling Reaction

Covalent organic frameworks (COFs) are crystalline porous solids with well-defined two- or three-dimensional molecular structures. Although the structural regularity provides this new type of porous material with high potentials in catalysis, no example has been presented so far. Herein, we report the first application of a new COF material, COF-LZU1, for highly efficient catalysis. The easily prepared imine-linked COF-LZU1 possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. Via a simple post-treatment, a Pd(II)-containing COF, Pd/COF-LZU1, was accordingly synthesized, which showed excellent catalytic activity in catalyzing the Suzuki-Miyaura coupling reaction. The superior utility of Pd/COF-LZU1 in catalysis was elucidated by the broad scope of the reactants and the excellent yields (96-98%) of the reaction products, together with the high stability and easy recyclability of the catalyst. We expect that our approach will further boost research on designing and employing functional COF materials for catalysis.

Mono dispersed SnO2 nanoparticles on both sides of single layer graphene sheets as anode materials in Li-ion batteries

A two step programmed method is developed to load mono dispersed SnO2 nanoparticles onto single layer graphene sheets. The SnO2-G composite has near mono dispersion of the SnO2 nanocrystals as well as a high SnO2 content of over 60 wt%. These outstanding features are desirable and enable the composite material to be an excellent anode material for Li-ion batteries.

Low-cost synthesis of flowerlike α-Fe2O3 nanostructures for heavy metal ion removal: adsorption property and mechanism.

Flowerlike α-Fe(2)O(3) nanostructures were synthesized via a template-free microwave-assisted solvothermal method. All chemicals used were low-cost compounds and environmentally benign. These flowerlike α-Fe(2)O(3) nanostructures had high surface area and abundant hydroxyl on their surface. When tested as an adsorbent for arsenic and chromium removal, the flowerlike α-Fe(2)O(3) nanostructures showed excellent adsorption properties. The adsorption mechanism for As(V) and Cr(VI) onto flowerlike α-Fe(2)O(3) nanostructures was elucidated by X-ray photoelectron spectroscopy and synchrotron-based X-ray absorption near edge structure analysis. The results suggested that ion exchange between surface hydroxyl groups and As(V) or Cr(VI) species was accounted for by the adsorption. With maximum capacities of 51 and 30 mg g(-1) for As(V) and Cr(VI), respectively, these low-cost flowerlike α-Fe(2)O(3) nanostructures are an attractive adsorbent for the removal of As(V) and Cr(VI) from water.

Microwave-assisted gas/liquid interfacial synthesis of flowerlike NiO hollow nanosphere precursors and their application as supercapacitor electrodes

A rapid method based on an efficient gas/liquid interfacial microwave-assisted process has been developed to synthesize flowerlike NiO hollow nanosphere precursors, which were then transformed to NiO by simple calcinations. The wall of the sphere is composed of twisted NiO nanosheets that intercalated with each other. Such hollow structure is different from widely reported flowerlike nanostructures with solid cores. An Ostwald ripening mechanism was proposed for the formation of the hollow nanostructures. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, energy-dispersive X-ray analysis, and N2adsorption-desorption methods. These flowerlike NiO hollow nanospheres have high surface area of 176 m2 g−1. Electrochemical properties show a high specific capacitance of 585 F g−1 at a discharge current of 5 A g−1 and excellent cycling stability, suggesting its promising potentials in supercapacitors.

Pd nanoparticles in silica hollow spheres with mesoporous walls: a nanoreactor with extremely high activity

A true nanoreactor composed of mesoporous silica hollow spheres and Pd nanoparticles residing inside the spheres shows superior activity in Suzuki coupling reactions with 99.5% yield in 3 min.

A Bi/BiOCl heterojunction photocatalyst with enhanced electron–hole separation and excellent visible light photodegrading activity

Under visible light irradiation, excited electrons in heterojunction structure of Bi/BiOCl were transferred into oxygen vacancies states, and then to the Bi metal nanoparticles, resulting in effective separation of electron–hole pairs. The heterojunction photocatalyst exhibited an extraordinary high activity in photodegradation of RhB dye and persistent organic pollutants, i.e. RhB was completely degraded in 2 minutes.

Superb Adsorption Capacity and Mechanism of Flowerlike Magnesium Oxide Nanostructures for Lead and Cadmium Ions

A facile method based on microwave-assisted solvothermal process has been developed to synthesize flowerlike MgO precursors, which were then transformed to MgO by simple calcinations. All the chemicals used (magnesium nitrate, urea, and ethanol) were low cost and environmentally benign. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, and N(2) adsorption-desorption methods. These flowerlike MgO nanostructures had high surface area and showed superb adsorption properties for Pb(II) and Cd(II), with maximum capacities of 1980 mg/g and 1500 mg/g, respectively. All these values are significantly higher than those reported on other nanomaterials. A new adsorption mechanism involving solid-liquid interfacial cation exchange between magnesium and lead or cadmium cations was proposed and confirmed.

Chrysanthemum-like α-FeOOH microspheres produced by a simple green method and their outstanding ability in heavy metal ion removal

Chrysanthemum-like α-FeOOH was synthesized via an environment-friendly H2O/ethylene glycol (EG) cooperating-mediated method. Based on detailed characterizations of the as-obtained hierarchical α-FeOOH nanostructure, the assembly process and possible formation mechanism were clarified. The as-obtained α-FeOOH nanomaterial exhibits a high adsorption performance in water treatment.

One-step synthesis of magnetic composites of cellulose@iron oxide nanoparticles for arsenic removal

Composite materials, containing magnetic nanoparticles and cellulose, were synthesized by one-step co-precipitation using NaOH–thiourea–urea aqueous solution for cellulose dissolution. The NaOH in cellulose solution acted as the precipitant of iron oxide nanoparticles, and low-cost cellulose was used as the template to promote the growing of nanoparticles in the cellulose matrix. The method provided a facile, “green” pathway for the fabrication of magnetic nanomaterials. The synthesized cellulose@iron oxide nanoparticles were characterized by FTIR, XRD, SEM, TEM, XPS, TG and VSM. The FTIR, XRD and XPS results demonstrated the formation of Fe2O3 nanoparticles in the composite materials after the co-precipitation. SEM and TEM characterization showed that the Fe2O3 nanoparticles were dispersed in the cellulose matrix due to the synergistic effect. Magnetometric measurements revealed that the resultant composites of cellulose@Fe2O3 nanoparticles exhibited a sensitive magnetic-induced behavior and could be easily separated from aqueous solution through the external magnetic field. The composite materials were applied to remove arsenic from aqueous solution. The results showed that the magnetic nanoparticle composites displayed excellent adsorption efficiency of arsenic compared with other magnetic materials reported, and the Langmuir adsorption capacities of the composites for the removal of arsenite and arsenate were 23.16 and 32.11 mg g−1, respectively.

Adsorption of heavy metal ions from aqueous solution by carboxylated cellulose nanocrystals

A novel nanoadsorbent for the removal of heavy metal ions is reported. Cotton was first hydrolyzed to obtain cellulose nanocrystals (CNCs). CNCs were then chemically modified with succinic anhydride to obtain SCNCs. The sodic nanoadsorbent (NaSCNCs) was further prepared by treatment of SCNCs with saturated NaHCO3 aqueous solution. Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb2+ and Cd2+. The effects of contact time, pH, initial adsorption concentration, coexisting ions and the regeneration performance were investigated. Kinetic studies showed that the adsorption equilibrium time of Pb2+ and Cd2+ was reached within 150 min on SCNCs and 5 min on NaSCNCs. The adsorption capacities of Pb2+ and Cd2+ on SCNCs and NaSCNCs increased with increasing pH. The adsorption isotherm was well fitted by the Langmuir model. The maximum adsorption capacities of SCNCs and NaSCNCs for Pb2+ and Cd2+ were 367.6 mg/g, 259.7 mg/g and 465.1 mg/g, 344.8 mg/g, respectively. SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb2+. NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles. The adsorption mechanisms of SCNCs and NaSCNCs were discussed.