Novel 3D Semiconducting Open-Frameworks based on Cuprous Bromides with Visible Light Driven Photocatalytic Properties.

Visible light driven photocatalysts based on crystalline microporous metal halogenides received much less attention compared with dense or composite oxide semiconductors. Using the well-known photosensitive transition metal-complexes [TM(2,2-bipy)3 ]2+ (TM=Fe, Co, Ni, Ru) as templates, a special three-dimensional (3D) metal halogenide framework of [TM(2,2-bipy)3 ]Cu4 Br6 was designed with [Cu4 Br4 ] cluster as 4-connected node. These microporous materials feature narrow band gaps and stable visible light driven photocatalytic properties including water reduction to provide H2 and photodegradation of organic pollutants. The study of electronic band structure shows that the TM complexes effectively prevent the recombination of photo-induced electron/hole pairs leading to excellent photocatalytic activity and photochemical stability. This work represents the first 3D microporous metal halogenides used as visible light driven photocatalyst to provide hydrogen energy.

A Chemical Blowing Strategy to Fabricate Biomass-Derived Carbon-Aerogels with Graphene-Like Nanosheet Structures for High-Performance Supercapacitors.

The efficient exploitation and utilization of low-cost and biomass-derived carbon materials will play an active role in developing sustainable energy storage systems. However, the difficult morphology control and incomplete activation limits their pervasive application in electrochemical energy storage. Inspired by the famous Chinese folk handicraft of sugar-figure blowing, biomass-derived carbon aerogels (GCA) with 2 D graphene-like thin nanosheets were fabricated by a simple chemical blowing strategy from a viscous agaric solution obtained through hydrothermal treatment of agaric. A chemical blowing agent (NH4 Cl) was used to effectively exfoliate the bulk biomass-derived carbon flake into 2 D graphene-like nanosheets, which resulted in a highly porous structure and high specific area (2200 m2 g-1 ) after the activation process. As a result, a high specific capacitance of 340 F g-1 at 3 A g-1 and a high specific energy of 25.5 Wh kg-1 at a power density of 2 kW kg-1 was obtained for the GCA electrode, which can be attributed to the abundant electrochemically active surfaces, short ion transport paths, and effective electrolyte infiltration.. This work demonstrates an effective and low-cost strategy to prepare hierarchical and well-organized porous biomass carbon materials with graphene-like nanosheets for high-performance supercapacitors.

Graphene Oxide-Graft-Poly(l-lactide)/Poly(l-lactide) Nanocomposites: Mechanical and Thermal Properties.

The surface modification of graphene sheets with polymer chains may greatly hinder its aggregation and improve its phase compatibility with a polymer matrix. In this work, poly(l-lactic acid)-grafted graphene oxide (GO-g-PLLA) was prepared via a simple condensation polymerization method, realizing its dispersion well in organic solvents, which demonstrated that the surface of GO changed from hydrophilic to hydrophobic. GO-g-PLLA can disperse homogeneously in the PLLA matrix, and the tensile test showed that the mechanical properties of GO-g-PLLA/PLLA were much better than that of GO/PLLA; compared with GO, only 3% GO-g-PLLA content can realize a 37.8% increase in the tensile strength for their PLLA composites. Furthermore, the differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results demonstrated that GO-g-PLLA shows a nucleating agent effect and can promote the crystallization of PLLA.

Comparison studies of hybrid lead halide [MPb2X7]2- (M = Cu, Ag; X = Br, I) chains: band structures and visible light driven photocatalytic properties.

By using transition-metal (TM) complex cationic dyes as structure-directing agents and photosensitizers, a series of inorganic-organic hybrid metal halides, namely, [TM(2,2'-bipy)3]AgPb2I7 [TM = Ni (1), Co (2) and Zn (3)], [Co(2,2'-bipy)3]CuPb2Br7 (4) and [TM(2,2'-bipy)3]AgPb2Br7 [TM = Ni (5) and Fe (6)], have been solvothermally prepared and structurally characterized. Compounds 1-3 feature 1D [AgPb2I7]2- chains built from the condensation of [Ag2I6] dimers and [Pb4I14] tetramers, and compounds 4, 5 and 6 contain similar 1D [CuPb2Br7]2- and [AgPb2Br7]2- chains, respectively. UV-Vis diffuse reflectance measurements reveal narrow band gaps of 1.75-2.18 eV for compounds 1-6, which lead to efficient and stable photocatalytic degradation activities over organic pollutants under visible light irradiation. Among the title compounds, sample 5 shows the highest photocatalytic degradation activity. The possible mechanism for their stable photocatalytic activities is proposed based on the experimental and theoretical studies.

Transition metal complex directed lead bromides with tunable structures and visible light driven photocatalytic properties.

With similar transition metal (TM) complex cations as structural directing agents (SDAs), six new hybrid lead bromides were synthesized and structurally characterized as [Co(2,2-bipy)3]2{[Co(2,2-bipy)]3Pb7Br24} (1), [Co(2,2-bipy)2Br]PbBr3 (2), [TM(phen)3]Pb2Br6 (TM = Co (3) and Ni (4)), [Co(2,2-bipy)3]Pb3Br9 (5) and [Co(2,2-bipy)3]Pb5Br13·CH3CN (6) with distinct structural types from zero-dimensional (0D) unit, one-dimensional (1D) chain to two-dimensional (2D) layer. Compound 1 contains the 0D {[Co(bipy)]3Pb7Br24}4- units built from the [Pb7Br24] ring attached by three unsaturated [Co(2,2-bipy)]2+ complexes via Co-Br bonds. Under the direction actions of different SDAs, compounds 2 and 3-4 contain two different types of [Pb2Br6]4- chains based on the same octahedral [PbBr6] units but with distinct connecting manners, respectively. Using the same [Co(2,2-bipy)3]3+ as SDA, compound 5 reveals a 1D [Pb3Br9]3- double chain, whereas compound 6 features a 2D complex [Pb5Br13]3- layer. The UV/vis diffuse-reflectance measurements reveal that the title compounds feature tunable band gaps of 1.70-2.29 eV. Under the visible light irradiation, sample 6 exhibits efficient and stable photocatalytic degradation activities over organic pollutants, which mainly originates from the multi-electronic effects of the TM complex cations. A possible photocatalytic mechanism is also proposed based on the radical trapping experiments and electronic band structural calculations.